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Scottish Court of Session Decisions
You are here: BAILII >> Databases >> Scottish Court of Session Decisions >> City Inn Ltd v Shepherd Construction Ltd  ScotCS CSOH_190 (30 November 2007)
Cite as:  CILL 2537, (2008) 24 Const LJ 590,  CSOH 190,  ScotCS CSOH_190, 2008 GWD 8-145,  BLR 269
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OUTER HOUSE, COURT OF SESSION
 CSOH NUMBER
LORD DRUMMOND YOUNG
in the cause
Pursuer: Keen, QC, Higgins; McGrigor Donald
Defender: Borland; Pinsent Masons
 The pursuers and the
defenders are respectively the employer and the contractor under a contract
dated 15 October and
date of possession specified in the Abstract of Conditions was
certain disputes arising between the parties were referred to
adjudication. The adjudicator, Mr John D Spencely, determined that the defenders were entitled to a
further five-week extension of time and directed the pursuers to repay them the
sum of £150,000. That determination is
not, of course, conclusively binding, and the matters argued before the
adjudicator fall to be determined in the present proceedings as if no
determination had been made by the adjudicator. The pursuers contend that the defenders are
not entitled to any extension of time beyond the contractual completion date,
defenders contend that they are entitled to an extension of time of 11 weeks
in total, with the result that the contractual completion date should be fixed
the foregoing background, the pursuers have raised the present action in which
they conclude for a range of remedies.
First, they seek declarator that the
Completion Date is
 After a period of adjustment the action proceeded to a debate before Lord Macfadyen (reported at 2002 SLT 781). That debate covered a number of issues arising out of the parties' pleadings. For present purposes it is sufficient to note that Lord Macfadyen considered the construction of clause 13.8 of the contract conditions. He concluded that it applied to late instructions which because of their content gave rise to a need to adjust the contract sum or to grant an extension of time, but that it did not apply to late instructions which, merely because of their lateness, gave rise to a need to adjust the contract sum or grant an extension of time. I refer to this issue further at paragraphs -. A reclaiming motion was marked against Lord Macfadyen's decision. This was heard by the Second Division and was refused (reported at 2003 SLT 885), although the decision proceeded to some extent on different grounds. The reclaiming motion did not, however, cover the question of whether clause 13.8 extended to late instructions which because of their lateness gave rise to a need for an adjustment of the contract sum or an extension of time.
 I intend to begin by setting out the contractual provisions that govern the parties' claims and considering the proper approach to the construction of such a contract. Thereafter I will deal with the evidence that was led, first in general terms and thereafter in relation to each of the three matters relied on by the defenders in order to justify an extension of time. Those three matters are: first the architect's instruction given on 23 March 1998 to use an alternative form of gasproof membrane; secondly the instructions given by the architect in relation to the roof steelwork and roof coverings; and thirdly the series of instructions issued by Keppie Architects after they became contract architect on or about 2 December 1998. After considering the justification for an extension of time, I will consider the construction of clause 13.8, and the issues of waiver and personal bar that arise in relation to that clause, in order to determine whether the defenders are entitled to an extension. Finally, I will consider the defenders' claim in the counterclaim for direct loss and expense that is alleged to have been caused by the various architect's instructions.
The relevant contractual provisions
 The parties' contract incorporates the conditions of the Standard Form of Building Contract (Private Edition with Quantities) (1980 edition), subject to a substantial number of amendments. Clause 24.1 of that form of contract states that if the Contractor fails to complete the Works by the Completion Date then the architect shall issue a certificate to that effect. Clause 24.2.1 provides for the payment of liquidated and ascertained damages in the event that the Contractor fails to complete the Works by the Completion Date; these are payable for the period between the Completion Date and the date of Practical Completion. The parties fixed the amount of liquidated damages at £30,000 per week.
"If and whenever it becomes reasonably apparent that the progress of the Works is being or is likely to be delayed the Contractor shall forthwith give written notice to the Architect of the material circumstances including the cause or causes of the delay and identify in such notice any event which in his opinion is a Relevant Event".
Clause 25.3.1 then provides:
"If, in the opinion of the Architect, upon receipt of any notice, particulars and estimate under clauses 188.8.131.52 and 25.2.2,
.1 any of the events which are stated by the Contractor to be the cause of the delay is a Relevant Event and
.2 the completion of the Works is likely to be delayed thereby beyond the Completion Date the Architect shall in writing to the Contractor give an extension of time by fixing such later date as the Completion Date as he then estimates to be fair and reasonable. The Architect shall, in fixing such new Completion Date, state:
.3 which of the Relevant Events he has taken into account and
.4 the extent, if any, to which he has had regard to any instruction under clause 13.2 requiring as a Variation the omission of any work issued since the fixing of the previous Completion Date,
Clause 25.3.3 further provides as follows:
"After the Completion Date, if this occurs before the date of Practical Completion, the Architect may, and not later than the expiry of 12 weeks after the date of Practical Completion shall, in writing to the Contractor ...
.1 fix a Completion Date later than that previously fixed if in his opinion the fixing of such later Completion Date is fair and reasonable having regard to any of the Relevant Events, whether upon reviewing a previous decision or otherwise and whether or not the Relevant Event has been specifically notified by the Contractor under clause 184.108.40.206...".
Relevant Events are specified in clause 25.4 (see clause 1.3). So far as material clause 25.4 provides as follows:
"The following are the Relevant Events referred to in clause 25:
.5 compliance with the Architect's instructions
5.1 under clauses... 13.2, 13.3 (except compliance with an Architect's instruction for the expenditure of a provisional sum for defined work)...
.6 the Contractor not having received in due time necessary instructions (including those for or in regard to the expenditure of provisional sums), drawings, details or levels from the Architect for which he specifically applied in writing provided that such application was made on a date which having regard to the Completion Date was neither unreasonably distant from nor unreasonably close to the date on which it was necessary for him to receive the same".
Clauses 13.2 and 13.3 deal respectively with variations and the expenditure of provisional sums.
"If the Contractor makes written application to the Architect stating that he has incurred or is likely to incur direct loss and/or expense in the execution of this Contract for which he would not be reimbursed by a payment under any other provision in this Contract ... because the regular progress of the Works or of any part thereof has been or is likely to be materially affected by any one or more of the matters referred to in clause 26.2; and if and as soon as the Architect is of the opinion... that the regular progress of the Works or of any part thereof has been or is likely to be so materially affected as set out in the application of the Contractor then the Architect from time to time thereafter shall ascertain... the amount of such loss and/or expense which has been or is being incurred by the Contractor; provided always that:
1. the Contractor's application shall be made as soon as it has become, or should reasonably have become, apparent to him that the regular progress of the Works or of any part thereof has been or was likely to be affected as aforesaid, and
2. the Contractor shall in support of his application submitted to the Architect upon request such information as should reasonably enable the Architect to form an opinion as aforesaid, and
3. the Contractor shall submit to the Architect... upon request such details of such loss and/or expense as are reasonably necessary for such ascertainment as aforesaid ".
Clause 26.2 provides as follows:
"The following are the matters referred to in clause 26.1:
.1 the Contractor not having received in due time necessary instructions (including those for or in regard to the expenditure of provisional sums), drawings, details or levels from the Architect for which he specifically applied in writing provided that such application was made on a date which having regard to the Completion Date was neither unreasonably distant from nor unreasonably close to the date on which it was necessary for him to receive the same;
.7 Architect's instructions issued
under clause 13.2 requiring a Variation or
under clause 13.3 in regard to the expenditure of provisional sums...
Interpretation of clauses 24 and 25: general considerations
 The effect of provisions such as are found in clauses 24 and 25 of the present JCT Standard Form was set out by Lord Fraser of Tullybelton in Percy Bilton Ltd v Greater London Council,  1 WLR 794, at 801:
"1. ...The general rule is that the main contractor is bound to complete the work by the date for completion stated in the contract. If he fails to do so, he will be liable for liquidated damages to the employer.
2. That is subject to the exception that the employer is not entitled to liquidated damages if by his acts or omissions he has prevented the main contractor from completing his work by completion date....
3. These general rules may be amended by the express terms of the contract.
4. In this case, the express terms of clause 23 of the contract [corresponding to the present clause 25] do affect the general rule. For example, where completion is delayed '(a) by force majeure, or (b) by reason of any exceptionally inclement weather' the architect is bound to make a fair and reasonable extension of time for completion of the work. Without that express provision, the main contractor would be left to take the risk of delay caused by force majeure or exceptionally inclement weather under the general rule".
Although these remarks relate to the 1963 JCT Standard Form, the general approach described that passage is equally applicable to the 1980 version of the contract. It follows that the extension of time provisions such as are found now in clause 25 are of critical importance in ensuring that the contractor is not subjected to liquidated damages for events that are outwith his control.
clauses are important for a further reason.
Under the JCT Standard Forms the employer is entitled to liquidated and
ascertained damages in the event that the contractor fails to complete the
works in time; in the present case such a provision is found in clause 24 of
the contractual conditions. Such clauses
are construed strictly, and if the contractor is prevented from completing in
time through the actings of the employer the
liquidated damages clause will be the treated as inapplicable. This point was made by Salmon LJ in Peak Construction (
"A clause giving the employer liquidated damages at so much a week or month which elapses between the date fixed for completion and the actual date for completion is usually coupled, as in the present case, with an extension of time clause. The liquidated damages clause contemplates a failure to complete on time due to the fault of the contractor. It is inserted by the employer for his own protection; for it enables him to recover a fixed sum as compensation for delay instead of facing the difficulty and expense of proving the actual damage which the delay may have caused him. If the failure to complete on time is due to the fault of both the employer and the contractor, in my view the clause does not bite. I cannot see how, in the ordinary course, the employer can insist on compliance with a condition if it is partly his own fault that it cannot be fulfilled.... I consider that unless the contract expresses a contrary intention the employer, in the circumstances postulated, is left to his ordinary remedy; that is to say, to recover such damages as he can prove flow from the contractor's breach. No doubt if the extension of time clause provided for the postponement of the completion date on account of delay caused by some breach of fault on the part of the employer, the position would be different. This would mean that the parties had intended the employer could recover liquidated damages notwithstanding that he was partly to blame for the failure to achieve the completion date. In such a case the architect would extend the date for completion, and the contractor would then be liable to pay liquidated damages for delay as from the extended completion date.
The liquidated damages and extension of time clauses in printed forms of contract must be construed strictly contra proferentem. If the employer wishes to recover liquidated damages for a failure by the contractors to complete on time in spite of the fact that some of the delay is due to the employer's own fault or breach of contract, any extension of time clause should provide, expressly or by necessary inference, for an extension on account of such fault or breach on the part of the employer".
Salmon LJ refers to fault or breach of contract on the part of the employer. Nevertheless, it is clear that his analysis applies equally to cases where the employer, through the contract architect, instructs a variation. style='mso-spacerun:yes'> A further point is of some significance. It seems implicit in Salmon LJ's analysis that an extension of time should still be available in cases where delay has been caused partly by the fault of the contractor and partly by the fault of the employer; reference is made to the employer's being "partly" to blame for the failure to achieve the completion date. The precise approach that should be followed in cases where delay is caused by concurrent causes, one of which is the fault of the contractor and one of which is not, is a matter of some importance in this case, and I return to it below.
"[I]t is right to examine the underlying contractual purpose of the completion date/extension of time/liquidated damages regime. At the foundation of this code is the obligation of the contractor to complete the works within the contractual period terminating at the completion date and on failure to do so to pay liquidated charges for the period of time by which practical completion exceeds the completion date. But superimposed on this regime is a system of allocation of risk. If events occur which are non-contractor's risk events and those events caused the progress of the works to be delayed, in as much as such delay would otherwise cause the contractor to become liable for liquidated damages or for more liquidated damages, the contract provides for the completion date to be prospectively or, under clause 25.3.3, retrospectively, adjusted in order to reflect the period of delay so caused and thereby reduce pro tanto the amount of liquidated damages payable by the contractor. Likewise, if the works are reduced by an omission instructed by the architect it may be fair and reasonable to reduce the contract period for completion prospectively or retrospectively and therefore to advance the completion date. In view of the inherent difficulties in predicting with precision the impact on the progress of the works of non-contractor's risk events, particularly when operating simultaneously with contractor's risk events the architect is given a power of retrospective adjustment of the completion date. The underlying objective is to arrive at the aggregate period of time within which the contract works as ultimately defined ought to have been completed having regard to the incidence of non-contractor's risk events and to calculate the excess time if any, over that period, which the contractor took to complete the works. In essence, the architect is concerned to arrive at an aggregate period for completion of the contractual works, having regard to the occurrence of non-contractor's risk events and to calculate the extent to which the completion of the works has exceeded that period".
A further issue arose in the same case, namely whether in fixing a the new completion date under clause 25 the architect should ignore the previous completion date and start his assessment of the extension of time from the date when the variation instruction was given, or should start with the existing completion date and postpone it to the extent considered fair and reasonable having regard to the delay caused by the requirement to execute the variation instructions. Colman J. favoured the latter approach (described as a "net" method). He said (at page 29):
"[O]ne again returns to the purpose of the architect's powers under clause 25. He looks back after the most recently-fixed completion date and, under clause 25.3.3, perhaps after practical completion, assesses the extent to which the period of contract time available for completion ought to be extended or reduced having regard to the incidence of the relevant events. His yardstick is what is fair and reasonable. For this purpose he will take into account amongst other factors the effect that the relevant event had on the progress of the works. Did it bring the progress of the works to a standstill? Or did it merely slow down the progress of the works? The function which he performs under clause 25.3.3 must as a matter of construction be in substance exactly analogous to that which he performs under clause 25.3.1. The difference is that under the former clause he does it after the completion date and not before it. But in both cases his objective must be the same: to assess whether any of the relevant events has caused delayed to the progress of the works and, if so, how much. He must then apply the result of his assessment of the amount of delay caused by the relevant events by extending the contract period for completion of the works by a like amount and this he does by means of postponing the completion date.
It will be perfectly obvious that unless the amount of time by which he postpones the completion date corresponds with the amount of delay time caused by the relevant events, the contractor will become potentially or actually liable for an amount of liquidated damages commensurate with a period which does not correspond with the amount of delay beyond the previously fixed completion date attributable to events of which he takes the risk under the contract".
 The foregoing discussion of clause 25 was described as a "valuable interpretation" by Dyson J in Henry Boot Construction (UK) Ltd v Malmaison Hotel (Manchester) Ltd, 1999, 70 Con LR 32 at paragraph 12. Certain features of the discussion are noteworthy. First, the scheme of sections 24 and 25 recognizes an allocation of risk: the contractor is bound to complete the works by the completion date except to the extent that delay is caused by events that are not at the contractor's risk. In general, as can readily be seen from the terms of clause 25.4, these are either events such as inclement weather which are extraneous to both parties or are events such as a variation which originate in a decision of the employer or the architect; the architect is for this purpose the employer's agent. Secondly, the architect's objective is to estimate the period within which the contract works as ultimately defined ought to have been completed, having due regard to the occurrence of non-contractor's risk events. The completion date is extended by that amount. Thirdly, this process involves certain inherent uncertainties. For example, a contractor's risk event and a non-contractor's risk event may operate concurrently in such a way that delay can be said to result from both, or indeed either. Another possibility is that a non-contractor's risk event merely slows the progress of the works, rather than bringing them to a halt. Because of these uncertainties, the architect is given power to adjust the completion date retrospectively, because it is clearly only with hindsight that the causative potency of each of the sources of delay can be properly assessed. Fourthly, the inherent uncertainties in the process are recognized in the scheme of clause 25. The architect is not expected to use a coldly logical approach in assessing the relative significance of contractor's risk events and non-contractor's risk events; instead, as the wording of both clause 25.3.1 and clause 220.127.116.11 makes clear, the architect is to fix such new completion date as he considers to be "fair and reasonable". That wording indicates that the architect must look at the various events that have contributed to the delay and determine the relative significance of the contractor's and non-contractor's risk events, using a fairly broad approach. Judgment is involved. It is probably fair to state that the architect exercises discretion, provided that it is recognized that the architect's decision must be based on the evidence that is available and must be reasonable in all the circumstances of the case. The decision must, in addition, recognize that the critical question is to determine the delay caused by non-contractor's risk events, and to extend the completion date accordingly. Fifthly, the completion date as so adjusted is not to be fixed without reference to the original completion date; instead, as Colman J. points out in the second of the passages quoted above, it is fixed by extending the contract period by an amount that corresponds to the delay attributable to the non-contractor's risk events.
 Further authority on the application of clause 25 is found in Henry Boot Construction (UK) Ltd v Malmaison Hotel (Manchester) Ltd, supra. In that case Dyson J., after referring to the analysis of Colman J. in Balfour Beatty, continued:
"13. [I]t is agreed that if there are two concurrent causes of delay, one of which is a relevant event, and the other is not, then the contractor is entitled to an extension of time for the period of delay caused by the relevant event notwithstanding the concurrent effect of the other event. Thus, to take a simple example, if no work is possible on a site for a week not only because of exceptionally inclement weather (a relevant event), but also because the contractor has a shortage of labour (not a relevant event), and if the failure to work during that week is likely to delay the works beyond the completion date by one week, then if he considers it fair and reasonable to do so, the architect is required to grant an extension of time of one week. He cannot refuse to do so on the grounds that the delay would have occurred in any event by reason of the shortage of labour.
15 It seems to me that it is a question of fact in any given case whether a relevant event has caused or is likely to caused delay to the works beyond the completion date in the sense described by Colman J. in the Balfour Beatty case. In the present case, the [employer] has... both a negative and a positive defence to the [extension of time] claim. The negative defence amounts to saying that the variations and late information etc relied on by the claimant did not cause any delay because the activities were not on the critical path, and on that account did not cause delay. The positive defence is that the true cause of the delay was other matters, which were not relevant events, and for which the contractor was responsible. In my view the respondent is entitled to advance these other matters by way of defence to the [extension of time] claim. It is entitled to say (a) the alleged relevant event was not likely to or did not cause delay e.g. because the items of work affected were not on the critical path, and (b) the true cause of the admitted delay in respect of which the claim for an extension of time is advanced was something else. The positive case in (b) supports and fortifies the denial in (a). The respondent could limit its defence to the claim by relying on (a), but in my view there is nothing in cl 25 which obliges it to do so. Likewise, when considering the matter under the contract, the architect may feel that he can decide the issue on a limited basis, or he may feel that he needs to go further, and consider whether a provisional view reached on the basis of one set of facts is supported by findings on other issues. It is impossible to lay down hard and fast rules. In my judgment, it is incorrect to say that, as a matter of construction of clause 25, when deciding whether a relevant event is likely to cause or has caused delay, the architect may not consider the impact on progress and completion of other events".
 Two important points emerge from these remarks. In the first place, in the application of clause 25, a relevant event may still be taken into account even though it operates concurrently with another matter that is not a relevant event. In other words, the "but for" rule of causation, that an event A will only be a clause of a result B if B would not have occurred but for A, has no application. In the example given by Dyson J. in paragraph 13, the delay would have occurred as a result of the shortage of labour by itself, regardless of the bad weather. On the approach to causation found in the general law of contract and delict, it could not be said that the bad weather caused the delay because the delay would have occurred in any event. Under clause 25, however, the architect may take the bad weather into account to the extent that he considers it fair and reasonable to do so. This perhaps emphasizes the general notion underlying clause 25, that it is designed to an achieve fairness as between the contractor and the employer, and the architect is given a reasonably wide discretion in order to achieve that result. In the second place, despite the width of the discretion given to the architect, before he can take any particular occurrence into account as a relevant event for the purposes of clause 25, he must be satisfied that the occurrence was a cause of the delay in completing the contract. This is illustrated by the example given in paragraph 15 of Dyson J.'s opinion.
 Dyson J.'s opinion in Henry Boot Construction (UK) Ltd v Malmaison Hotel (Manchester) Ltd was considered by Judge Richard Seymour QC in Royal Brompton Hospital NHS Trust v Hammond (No 7), (2001) 76 Con LR 148, at paragraph 31. In that passage Judge Seymour gave a further explanation of what is meant by "events operating concurrently". He drew a distinction between on one hand a case where work has been delayed through a shortage of labour and a relevant event then occurs and on the other hand a case where works are proceeding regularly when both a relevant event and a shortage of labour occur, more or less simultaneously. Judge Seymour considered that Dyson J. had only been concerned with the latter situation, and not with the former; in the former situation the relevant event had no effect upon the completion date. I have some difficulty with this distinction. It seems to turn upon the question whether the shortage of labour and the relevant event occurred simultaneously; or at least it assumes that the shortage of labour did not significantly predate the relevant event. That, however, seems to me to be an arbitrary criterion. It should not matter whether the shortage of labour developed, for example, two days before or two days after the start of a substantial period of inclement weather; in either case the two matters operate concurrently to delay completion of the works. In my opinion both of these cases should be treated as involving concurrent causes, and they should be dealt with in the way indicated in clause 25.3.1 by granting such extension as the architect considers fair and reasonable.
 It is in any event clear from older authority that the fact that delay has been caused by matters for which the contractor is responsible will not deprive the contractor of his right to claim an extension of time for delay caused by a relevant event. That is essentially the ratio of Wells v Army and Navy Co-operative Society, 1903, 86 LT 764. A more modern statement of this principle is found in S.M.K. Cabinets v Hili Modern Electrics Pty Ltd,  VR 391, a decision of the Supreme Court of Victoria. style='mso-spacerun:yes'> In that case, Brooking J., whose opinion was concurred in by the other judges of the court, stated (at 398):
"The sole remaining matter is that of the soundness of the ground on which the arbitrator in fact rejected the defence of prevention [that is, acts of the employer that prevent the contractor from completing on time]. He evidently considered that where acts or omissions of a proprietor do in fact substantially delay completion, the proprietor nonetheless cannot be sent to have prevented the contractor from completing by the relevant date unless the contractor would have been able to complete by that date had it not been for the supposed prevention.... But it has been accepted for more than one hundred years that this is not the law. The cases are all one way".
Cases were then cited from
"The principle of the decision is not as clear as one would wish, but appears to be that if the supposed prevention was such as would in ordinary circumstances have made it impossible for the contractor to complete in time, then prevention has in law occurred, notwithstanding that the contractor may in fact have disabled himself by his own delays from completing by the due date".
 While delay for which the contractor is responsible will not preclude an extension of time based on a relevant event, the critical question will frequently, perhaps usually, be how long an extension is justified by the relevant event. In practice the various causes of delay are likely to interact in a complex manner; shortages of labour will rarely be total; some work may be possible despite inclement weather; and the degree to which work is affected by each of these causes may vary from day to day. Other more complex situations can easily be imagined. What is required by clause 25 is that the architect should exercise his judgment to determine the extent to which completion has been delayed by relevant events. The architect must make a determination on a fair and reasonable basis. Where there is true concurrency between a relevant event and a contractor default, in the sense that both existed simultaneously, regardless of which started first, it may be appropriate to apportion responsibility for the delay between the two causes; obviously, however, the basis for such apportionment must be fair and reasonable. Precisely what is fair and reasonable is likely to turn on the exact circumstances of the particular case. A procedure of that nature is in my opinion implicit in the wording of clause 25.3.1 and .3; both of these provisions direct the architect to give an extension of time by fixing a Completion Date that he considers to be fair and reasonable.
foregoing construction of clause 25 is in my opinion supported by the approach
taken to concurrent causes of delay in Federal tribunals in the
"It is well settled that the failure of a contractor to prosecute the contract work with the efficiency and expedition requisite for its completion within the time specified by the contract does not, in and of itself, disentitle the contractor to extensions of time for such parts of the ultimate delay in completion as are attributable to events that are themselves excusable, as defined in [the relevant extension of time clause, corresponding to clause 25]. Where a contractor finishes late partly because of a cause that is excusable under this provision and partly because of a cause that is not, it is the duty of the contracting officer to make, if at all feasible, a fair apportionment of the extent to which completion of the job was delayed by each of the two causes, and to grant an extension of time commensurate with his determination of the extent to which the failure to finish on time was attributable to the excusable one. Accordingly, if a event that would constitute a excusable cause of delay in fact occurs, and if that event in fact delays the progress of the work as a whole, the contractor is entitled to an extension of time for so much of the ultimate delay in completion as was the result or consequence of that event, notwithstanding that the progress of the work may also have been slowed down or halted by a want of diligence, lack of planning, or some other inexcusable omission on the part of the contractor".
This approach recognizes the fact that culpable and non-culpable causes of delay will frequently coexist and interact, and permits the contracting officer, equivalent to the architect under the JCT Forms, to apportion the delay between the culpable and non-culpable causes. That seems to me to be the only way in which a fair result can be achieved in such cases, and in my opinion such an approach is contemplated by the wording of clause 25. I should add that the decision of the Board of Contract Appeals in Chas. I. Cunningham Co. was followed in Sun Shipbuilding & Drydock Co., ANBCA 11300, 68-1 BCA (CCH) P7054 (1968).
for the pursuers founded strongly on the opinion of the court in John Doyle Construction Ltd v Laing Management (
 In the course of their submissions counsel for the pursuers advanced a number of legal propositions. First, it was said that for a contractor to establish an entitlement to an extension of time in respect of delay arising out of a relevant event he must establish that the delay was caused by the relevant event, as opposed to any other pre-existing or concurrent matter for which the contractor himself is responsible; and he must establish the extent of such delay. In my opinion that proposition is too broadly stated. It is correct that the contractor must establish that delay was caused by a relevant event, and the extent of the delay; nevertheless, I am of opinion that concurrent causes should be treated in the manner discussed in paragraph  above. The second proposition advanced for the pursuers was that, if a relevant event can be shown to be the "dominant or operative" cause of a delay, the party responsible for that event will be held responsible for the delay. I agree that it may be possible to show that either a relevant event or a contractor's risk event is the dominant cause of that delay, and in such a case that event should be treated as the cause of the delay. A similar principle was recognized in Doyle, at paragraph  of the opinion of the court; the principle is derived from older case of Leyland Shipping Company Ltd v Norwich Union Fire Insurance Society Ltd,  AC 350. Those cases refer to the "dominant" or "proximate" cause. The pursuers' submission went further, and referred to the "dominant or operative" cause of the delay. In my opinion this extension is not legitimate. Indeed, I have difficulty in seeing what the word "operative" adds to the notion of causation; a cause can only be relevant if it is operative, and that is as true of concurrent causes as it is of single or "dominant" causes.
 The pursuers' third proposition was that a variation instructed during a period when the contractor is already in delay will not absolve the contractor of responsibility for that pre-existing delay, unless it is proved that the delay resulted from the variation. style='mso-spacerun:yes'> As stated, this is correct. Nevertheless, the "delay" that matters is delay to the Completion Date. If the contractor is, through his own fault, in delay before a relevant event, that may explain delay that follows the Completion Date. Alternatively, it may be possible for the contractor to demonstrate that he would have made up the delay caused by his own fault, and that the delay beyond the Completion Date results from the variation. style='mso-spacerun:yes'> It is all a question of fact. The pursuers' fourth proposition was in two parts: first, it is a defence to a claim that a variation or late instruction caused delay to establish that the matter to which the variation or late instruction was issued was not on the critical path; secondly, it is also a defence that the claimed delay was in fact due to other events. The first of these contentions was not, I think, in dispute, although the parties were sharply in dispute as to where the critical path lay in the progress of the contractual works. The second contention, however, is perhaps stated rather simplistically. In practice causation tends to operate in a complex manner, and a delay to completion may be caused in part by relevant events and in part by contractor default, in a way that does not permit the easy separation of these causes. In such a case, the solution envisaged by clause 25 is that the architect, or in litigation the court, must apply judgment to determine the extent to which completion has been delayed by relevant events. In an appropriate case apportionment of the delay between relevant events and contractor's risk events may be appropriate. Precisely when and how that should take place is a question that turns on the precise facts of the case.
The time for issuing instructions
further legal issue is relevant to the present case: this relates to the time
at which the architect is obliged to issue instructions in terms of clause
25.4.6. The relevant event specified in
that clause is "the contractor not having received in due time necessary
instructions". The expression
"in due time" was said in Percy
Bilton Ltd v Greater
"What is a reasonable time does not depend solely upon the convenience and financial interests of the [contractors]. No doubt it is in their interest to have every detail cut and dried on the day the contract is signed, but the contract does not contemplate that. It contemplates further details and instructions being provided, and the engineer is to have a time to provide them which is reasonable having regard to the point of view of him and his staff and the point of view of the [employer], as well as the point of view of the contractors.
In determining what is a reasonable time as respects any particular details and instructions, factors which must obviously be born in mind are such matters as the order in which the engineer has determined the works shall be carried out..., whether requests for particular details or instructions have been made by the contractors, whether the instructions relate to a variation of the contract which the engineer is entitled to make from time to time during the execution of the contract, or whether they relate to part of the original works, and also the time, including any extension of time, within which the contractors are contractually bound to complete the works".
The first of the specific factors mentioned by Diplock J. is not strictly relevant to the present case, since under the parties' contract the architect is not given power to determine the order in which the works should be carried out. Instead, the contractor determines the programme. Nevertheless, the contractor's programme is clearly relevant in determining what is a reasonable time for giving any particular instruction. The other three factors are all relevant. In relation to the last, the time within which the contractor is contractually bound to complete the works, a difference arose between the parties. Counsel for the defender submitted that the contractual completion date, allowing for any extension, must always set a criterion against which the timing of instructions should be judged. Counsel for the pursuers, by contrast, submitted that, where the contractor's progress was such that he clearly would not complete by the contractual completion date, it was sufficient that the instructions were in sufficient time to meet his actual progress. In my opinion the current contractual completion date must normally be relevant, for two reasons. First, there is the possibility that the contractor will take special measures to accelerate progress. That is no doubt subject to an exception when the Completion Date is past, but in that event it may be that instructions should have been given prior to the Completion Date. The second reason is more general: the contractual provisions expressly envisage that information will be provided by the architect to the contractor to enable completion in accordance with the contractual Conditions (clause 5.4), and those conditions include the important obligation (clause 23) to proceed regularly and diligently with the works and to complete the works on or before the Completion Date. Nevertheless, all of the factors mentioned by Diplock J., subject to the qualification mentioned above in relation to the first, are potentially relevant in determining what is a reasonable time for the provision of information. Ultimately that question is a question of fact, and will depend upon the whole circumstances of the particular case.
Competing approaches of parties' expert witnesses
must now consider the factual issues that arise in this case. The defenders
relied on expert evidence from their own programming expert, Mr Alan Whitaker,
and on evidence from two witnesses of fact, Mr Kevin Cornish, who was the
defenders' senior site manager for most of the duration of the contract, and Mr
David Dibben, who at the time of the contract was the
defenders' regional manager for South West England and South Wales. The pursuers relied solely on the evidence of
their programming expert, Mr Nigel Lowe.
They did not lead any witnesses of fact.
In relation to the witnesses of fact, I should state that I found both Mr Cornish
and Mr Dibben to be credible and generally
reliable witnesses. Mr Cornish, in
particular, impressed me as having a good knowledge and understanding of what
had happened as the contract works progressed.
Before I examine the evidence in detail, however, I consider it
appropriate to consider the different approaches taken by the parties' two
expert witnesses. For the defenders, who
led at the proof, evidence was given by Mr Alan Whitaker. Mr Whitaker was a Chartered Civil
Engineer and a member of the Chartered Institute of Arbitrators. He graduated as a Bachelor of Technology in
Civil Engineering; thereafter, from 1966 to 1988, he had worked for a number of
major contractors as an engineer, site agent or contracts manager. The projects on which he worked were clearly
very diverse; they are set out in Appendix A to his report No 7/156 of
process. His experience extended to
design and construction in industrial building projects. It is fair to say that his involvement was
generally with large and intricate construction projects. In 1988 he established an independent
practice, Alan E Whitaker & Associates, to provide computer-based planning
services in the construction industry.
This involved the provision of critical path analysis. As an independent consultant, Mr Whitaker
was involved in a number of substantial projects. His practice continues in that area, but from
1993 onwards most of his work has been in the preparation, negotiation and
settlement of claims, and acting as an expert witness in arbitration and
litigation. He clearly had substantial
experience in that area. Mr Whitaker
produced a first report in the present case dated
 As I have mentioned, Mr Whitaker produced two reports. His position changed in number of respects between the two reports. He explained that this had occurred because he had obtained a significant amount of further information during the intervening period. In particular, the pursuers had disclosed the diaries and weekly reports of the clerk of works. He had met Mr Nigel Lowe, the pursuers' expert, and had discussed the as-built programme with him. In addition, he had been given access to further documents in the possession of the defenders and had been provided with further information by the defenders and by Mr Kevin Cornish, who had been their senior site manager on the project. I think that the information provided by Mr Cornish is important; as indicated in the last paragraph, I considered him an impressive witness.
 Mr Whitaker described his approach as follows (No 7/8 of process, paragraphs 1.5-1.11). He first examined the programme against which the works were being constructed and tested it for reasonableness and completeness. He then examined the factual evidence to determine where time on the project was critically lost and identify the cause or causes of that loss of time. He concluded that three weeks had been lost during weeks 6, 7 and 8 of the contract; the cause of the loss in Mr Whitaker's opinion was additional work instructed in connection with the gas venting scheme (see paragraph  below). He was further of opinion that five weeks were lost between weeks 27 and 32 of the contract. He considered that the cause of this loss of time was a late instruction by the architect, RMJM, to vary the roof coverings from a built-up system to the Stramit Speedeck system. The lost time was in part concurrent with the effect of the loss of time caused by the gas venting works. The effect of the late instruction was that work on the roof steelwork began late; the design of the steelwork was dependent upon the roofing system that was used. In addition, the start of the roof coverings was similarly delayed by five weeks, because the late instruction had led to delay in the procurement of the roof coverings. Finally, Mr Whitaker thought that six weeks were lost between weeks 44 and 52 of the contract. This was caused by the lateness of a substantial number of architect's instructions varying the works following the dismissal of a RMJM and their replacement as architect by Keppie Architects. Mr Whitaker's overall view was that 11 weeks (6 weeks plus 5 weeks) were critically lost during construction. style='mso-spacerun:yes'> On that basis, he considered that a fair and reasonable measure of any extension of time to which the defenders might be entitled was 11 weeks.
 Mr Whitaker was critical of the as-built critical path analysis used by Mr Lowe; I deal with his specific criticisms that analysis at paragraphs - below. In evidence, Mr Whitaker stated that he had considered undertaking a critical path analysis, but decided not to do so. He did not have access to an electronic version of the defenders' original programme for the project, and because of this it was impossible to identify the defenders' original critical path through the programme. Nevertheless, making use of his experience in programming, Mr Whitaker had attempted to replicate what he surmised might be the logic of the defenders' original programme; he stated, however, that he had no great confidence that his version of that programme was either correct or complete. Mr Whitaker stated that to continue with a critical path analysis based on logic that he knew not to be completely correct would have meant that he could not be sure of the evidence that he was giving to the court. Rather than following such a course, he adopted the method described in the last paragraph. In his initial report (No 7/156 of process, at paragraph 2.11) he stated that the task was to identify where critical time had been lost on the project, and that in order to do that it was necessary to understand the construction process involved in that project. In this way it was possible to identify "events in that construction process which logic, experience and common sense tell you will be critical to completion of the works". Mr Whitaker explained that he meant by that that delay to any of these critical points would mean delay to completion of the works as a whole unless exceptional measures were taken to recover lost time. Mr Whitaker identified events in the construction programme that he considered to be critical; these are discussed subsequently. Mr Cornish was asked about the various events that Mr Whitaker identified as critical and confirmed in relation to each that he also considered them to be critical for completion of the works.
 The pursuers criticized Mr Whitaker's approach to the case. They referred in particular to his failure to undertake a critical path analysis of the present project. That might be explained by the fact that Mr Whitaker preferred to use the as-planned v as-built method. Nevertheless, the weakness of that method was that, as Mr Whitaker acknowledged, it does not identify the critical path and therefore needs to be used with great care and understanding of the processes in the whole of the project. The pursuers submitted that an expert could only give a meaningful opinion as to which activities in a project are critical on the basis of an as-built critical path analysis, such as that carried out by Mr Lowe. For that reason it was suggested that I should treat with caution, and indeed scepticism, Mr Whitaker's opinion. The pursuers also pointed out that Mr Whitaker had significantly changed his opinion in relation to the delay arising from the gas venting scheme between his original report of October 2003 and his later report of March 2004 (No 7/8 of process). In justifying this, Mr Whitaker had relied on the fact that in preparing his initial report he had a limited amount of time and relied on Mr Lowe's as-built programme for his analysis; at that time he had not seen the Clerk of Works' diaries and weekly reports. The pursuers were nevertheless critical of Mr Whitaker on the basis that he provided a detailed opinion on the basis of inadequate information.
 In my opinion the pursuers clearly went too far in suggesting that an expert could only give a meaningful opinion on the basis of an as-built critical path analysis. For reasons discussed below (at paragraphs -) I am of opinion that such an approach has serious dangers of its own. I further conclude, as explained in those paragraphs, that Mr Lowe's own use of an as-built critical path analysis is flawed in a significant number of important respects. On that basis, I conclude that that approach to the issues in the present case is not helpful. The major difficulty, it seems to me, is that in the type of programme used to carry out a critical path analysis any significant error in the information that is fed into the programme is liable to invalidate the entire analysis. Moreover, for reasons explained by Mr Whitaker (paragraphs - below), I conclude that it is easy to make such errors. That seems to me to invalidate the use of an as-built critical path analysis to discover after the event where the critical path lay, at least in a case where full electronic records are not available from the contractor. That does not invalidate the use of a critical path analysis as a planning tool, but that is a different matter, because it is being used then for an entirely different purpose. Consequently I think it necessary to revert to the methods that were in use before computer software came to be used extensively in the programming of complex construction contracts. That is essentially what Mr Whitaker did in his evidence. Those older methods are still plainly valid, and if computer-based techniques cannot be used accurately there is no alternative to using older, non-computer-based techniques.
 In relation to the pursuers' other criticisms of Mr Whitaker, I do not draw an adverse inference from his change of position in relation to the effects of the gas venting instruction. His change of position was made clearly in his second report, and the reasons for it were stated in detail. His change of position was based on the receipt of further information. To change one's opinion in the light of further information seems to me to show openness of mind and a basic fairness of approach. Moreover, Mr Whitaker did indicate that his first report was produced under significant time constraints. Overall, I found Mr Whitaker's evidence to be generally cogent and persuasive, and for the most part I have adopted his analysis.
 The pursuers also criticized the defenders' overall position on programming. They pointed out that Mr Whitaker had only been provided with a hard copy of the defenders' original construction programme, not with a computer version. The programme had, however, been based on a computer programme known as Suretrack; this is a programme that is commonly used in the construction industry. Mr Whitaker had agreed that one reason for generating a construction programme using Suretrack software was to enable the revisal and updating of the construction programme as works proceeded. Mr Whitaker had also indicated concern that the defenders had not, during the contract works, updated their Suretrack programme, although he stated that that was not untypical. He acknowledged that critical part analysis used proactively is "a fantastic tool", in that it can demonstrate as works proceed whether there is any flaw in the logic of the programme. The use of a programme such as Suretrack permits the contractor to update his programme as construction progresses and to allow for the impact of events on the construction programme. Mr Lowe's evidence was that in his experience most contractors who use such software will continue to use it as the works proceed to monitor the progress of the works. In failing to do so, the defenders had hampered the presentation of the case and had also significantly hindered the experts in their analysis of the instructions and delays on the overall progress of the works. The absence of the programme also made it much more difficult to discover the contractor's original logic. In September 1999 the defenders produced delay charts using Suretrack for the purposes of adjudication proceedings, which suggested that the programme had existed at that time.
 I accept that understanding what had happened during the progress of the works might have been a great deal easier if the defenders' original Suretrack programme had been available, and in particular if it had been updated as the works proceeded. Nevertheless, I am bound to approach the case on the basis of the evidence that is available. The programme was not available; in any event, even if it had been available, it is clear that it was not updated as the works proceeded, and for that reason I doubt whether it would have been of any real assistance. While the defenders' loss of the programme at a time when disputes had arisen between the parties might be regarded as culpable, I do not think that that it is the loss of the programme that has caused the difficulties; the fundamental problem is rather the failure to update the programme as works proceeded. The original programme is available in a hard copy, and a view of the logic of the programme can be obtained from that. In my view, on the basis of Mr Whitaker's evidence, failure to update the programme is relatively common, and it is easy to understand why that is so. In all the circumstances I do not think that I can draw any significant adverse inference from the fact that the defenders' records were less good than they might have been in other circumstances.
 Mr Lowe carried out a critical path analysis of the project, and on that basis produced a filtered as-built programme (No 7/161 of process). The critical path of a construction contract is a sequence of activities through the project from start to finish the sum of whose durations determines the overall duration of the project. Consequently any delay to the progress of an activity on the critical path may cause the duration of the overall project to be extended. Thus a critical path analysis depends upon a logical sequence of activities; each activity falling on the critical path can only be performed when a certain stage has been reached in a logically preceding activity. That stage varies; on occasion the succeeding activity may be in a position to start as soon as the preceding activity has started; in other cases it is necessary that the preceding activity should have finished before the succeeding activity can start; in yet other cases it will suffice if the preceding activity has been carried out in part to enable a start on the succeeding activity. If an activity is on the critical path to completion, any delay in starting the activity or any increase in the length or duration of the activity will produce a consequential effect on the date for completion. Mr Lowe carried out a critical path analysis of the project as built, rather than an analysis of the planned project. In an as-built analysis, it is known what the contractor actually did; for example, it may be known that the contractor in fact waited to complete one task before he started work on another, even though logically there was no reason for waiting. In such a case the resulting delay would be incorporated into an as-built programme. That affects the logic of the programme, and links must be inserted to show what was actually done, even though in theory a successor task could have started earlier.
 In evidence Mr Lowe stated that after producing his as-built programme he began his analysis by identifying, by inspection, whether any of the logic paths in the as-built situation were consistent with the planned situation as shown in the defenders' construction programme. He then looked at the records of the project to discover whether the defenders had departed from their planned logic. One example of this that he noted was the use of temporary sealing when construction reached the fourth and sixth floors respectively; this was designed to make the building temporarily weatherproof, to enable weather-dependent tasks to be carried out on lower floors. Thereafter Mr Lowe started from the date when completion was actually achieved and identified the last activity before completion. He then worked backwards towards the start of the project to determine the logic links in the programme as built, and then using those links he rescheduled the programme. This identified the critical path. It was accepted by the pursuers that an element of subjective judgment was required in this exercise; nevertheless, Mr Lowe indicated that in exercising that judgment he relied on his knowledge and experience of programming in the construction industry. Mr Lowe described the method that he used in handling the programme. Tasks were linked in three ways: first, logic lags could be used to maintain the correct time relationship between the tasks; secondly, it was possible to insert contractor or employer defaults to fill in the time gap between what was considered to be the reasonable logic and the time when an activity actually began; and thirdly, it was possible to use start flags to constrain a task to an actual start date. Mr Lowe also stated that it is necessary in a programme to take account of four types of restraints that may have an effect on progress. These are technological restraints (based on the method of construction), management restraints (based on decisions taken by the contractor), health and safety restraints and resources restraints (caused by lack of resources).
 Using this method, Mr Lowe expressed the opinion that none of the matters relied on by the defenders to support their claims for an extension of time had caused any delay. He came to that conclusion on the basis that none of those matters fell on the critical path through the project; that critical path was set out in his as-built programme (in No 7/61 of process). Mr Lowe's reasons for this conclusion are set out at length in his reports.
 Mr Whitaker criticized the method of delay analysis that Mr Lowe had adopted; in particular, he was critical of the use of an as-built critical path analysis. He stated that a critical path analysis involves identification of the duration of the relevant activities, based on the as-built records, and the logic links between those activities. The identification of the correct logic links was of vital importance. Problems arose with a critical path analysis when logic links were incorporated when they should not be there, or if logic links were inserted which were not wholly correct, or if necessary links were omitted. If a mistake was made in one logic link, that was liable to produce an error in the identification of the activities that were critical to completion of the works, and that in turn could invalidate the critical path shown in the relevant programme. If a number of erroneous links were identified, Mr Whitaker stated that it would definitely be the case that the critical path identified in the programme would not be correct.
 Mr Whitaker identified what he considered to the errors in the logic links inserted by Mr Lowe in his as-built programme (number 7/161 of process). He further suggested that Mr Lowe had omitted certain important links from his programme. The errors referred to by Mr Whitaker were as follows:
(i) Line 8: AB Construct ground floor slab. The bar representing this activity was not split to reflect that the ground floor slab was poured in two pours. In cross-examination, Mr Lowe accepted that this would require the start of the activity to be linked to an earlier activity; otherwise activities that were critical would become non-critical on rescheduling, and the critical path might be altered.
(ii) Line 12: AB construct 2nd floor to 3rd floor. This activity was not shown as critical on Mr Lowe's programme, but in cross-examination he accepted that it should have been shown as critical. Mr Lowe further accepted that the link shown coming in to the activity from line 10 was erroneous, as it omitted a floor of the building. Finally, Mr Lowe accepted that a link was missing from his programme; he stated that there should be a start-start (SS) link from line 11 to line 12.
(iii) Line 13: AB construct 3rd floor to 4th floor. Mr Lowe accepted in cross-examination that the link from line 11 to line 13 (13FS2d, signifying a finish-start link with a time lag of two days) was erroneous; once again a floor was omitted. Mr Lowe further accepted that it was wrong to indicate that the start of the activity at line 13 depended upon the finish of the activity at line 11; instead, the link should have been a SS link from line 12 to line 13.
(iv) Line 14: AB construct 4th floor to 5th floor. This activity is shown as non-critical in Mr Lowe's programme, but in cross-examination he accepted that this was wrong and that the activity should be shown as critical. Mr Lowe further accepted that the link to the start of line 14 from the end of line 12 (14FS6d) was incorrect; instead the programme should have shown a SS link from line 13 to line 14.
(v) style='font:7.0pt "Times New Roman"'> Line 15: AB construct 5th floor to 6th floor. Mr Lowe accepted in cross-examination that the link to the start of line 15 from the end of line 13 (15FS1d) was incorrect, and it was also incorrect to state, as the programme indicated, that the criticality of the activity at line 15 depended on the activity at line 13. The link should rather have been a SS link from line 14 to line 15.
style='font:7.0pt "Times New Roman"'>
Line 15: AB construct 5th floor to 6th floor. A central feature of Mr Lowe's evidence
was the view that neither the roof steelwork nor the roof cladding was on the
critical path. The first link out of
line 15 was to the reinforced concrete stair flights at line 38 (38FF1d), that
link being shown as critical. Work on
the reinforced concrete stair flights is shown as finishing on
style='font:7.0pt "Times New Roman"'>
Line 49: AB load out plant room equipment. The plant room was situated at roof level,
under the cladding. The last part of
this activity was the hoisting in of the chillers, which took place on
style='font:7.0pt "Times New Roman"'>
Line 20: AB roof cladding.
In Mr Lowe's programme this work is shown in a number of sections,
the last of which refers to "penetrations". The final successor link from this line is to
snagging, shown as 60FS0d. This link is
shown as critical. On the programme that
critical link is shown to snagging taking place on or about
(ix) Line 50: AB plant room installation. A link joins line 50 to soil stacks at line 43, the link being 50FS-1d. When cross-examined, Mr Lowe accepted that it was probably not the case that the contractor could only start installing plant in the plant room one day before the completion of the soil stacks. If that is so, the link would be incorrect.
(x) Line 20: AB roof cladding. The only link shown from this activity to any mechanical and electrical activity is to soil stacks at line 43 (identified as 43FS9d). Mr Lowe considered that link to be critical, but he thought that the only mechanical and electrical activity that depended on the roof cladding was the testing of the soil stacks. Mr Lowe further stated (day 24, 3.45) that there was no practical relationship between the roof cladding and the second fix mechanical and electrical work. He justified that position on the basis that the defenders had installed temporary covers at 4th and 6th floor level over the 18 voids created by the risers that run up through the building. He conceded, however, that once the plant and equipment were in place at the plant room level a roof would be necessary in order to take the covers off the plant and equipment and to allow connections to be made down through the building (day 25, 10.11). That would require the temporary covers to be removed. On this basis, it seems that the roof must be critical, at least once the plant was put in place and the contractor wished to connect it to the services running through the building. This is a point of some importance, and I return to it at paragraph .
(xi) Line 17: skim plaster finish to bedroom walls and ceilings. The only successor link is to line 57, decoration, and is shown as 57FS1d. Both of these activities are shown as critical in Mr Lowe's programme, and Mr Lowe accepted that the logic link between them is critical. In cross-examination, however, he conceded that this critical link was wrong (day 25, 10.36). He accepted that the link should have been start to start rather than finish to start; it is obvious why this is so, since decoration could clearly begin as soon as the earlier parts of the skim plaster had dried. Mr Lowe was then asked what would happen if the erroneous link were deleted, the correct link inserted and the programme rescheduled; he believed that the skim plaster activity at line 17 became non-critical. Mr Whitaker specifically disagreed with Mr Lowe's programme at this point, as did Mr Cornish.
Line 54: ceramic tiling.
Mr Lowe records the finish date for this activity as being
(xiii) Line 52: AB stud partitions and dry linings. Mr Lowe's programme does not show any link from this activity to any mechanical and electrical activity. He stated in evidence, however, that in the area between the bedrooms and the bathrooms the stud partition walls would be erected with the second fix electrical and plumbing work within them; metal studs and one side of the plasterboard would be erected, followed by the electrical and plumbing work, followed by the second side of plasterboard. On this basis Mr Lowe accepted (day 26, 10.22) that there was a relationship between the stud partitions and second fix wiring, shown at line 44. No such link is reflected in Mr Lowe's programme, although stud partitions and dry linings are shown as a critical activity.
Line 30: install temporary windows -- timber frame and
polythene. In this case a link is shown
to first fix joinery, at line 53, in the form 53SS9D; that indicates that first
fix joinery cannot start until nine days after the start of the installation of
temporary windows and polythene sheets.
That link is between two critical activities, and should therefore be
regarded as critical. Mr Cornish,
however, considered that little work was involved in first fix joinery, and that
such work as there was not dependent upon the temporary windows; thus there was
no relationship between the two. Mr Whitaker
supported this view; first fix joinery referred to work in the bathroom area,
but this was not near the outer walls of the building and was therefore not
dependent upon the temporary windows. On
this basis it appears that the link shown by Mr Lowe is erroneous. Mr Lowe further showed a link between
temporary windows at line 30 and ceramic tiling at line 54, in the form
54SS12d. Both of these activities are
shown as critical. Mr Whitaker
stated that, before any tiling could be done, the contractor required first to
erect the stud partition walls on which the tiling was placed. If there were any link with the temporary
windows, accordingly, it would be expected that this would run through the stud
partitioning. No such link was shown,
however, and in fact the stud partitioning work started on
Line 19: grout in steelwork.
A successor link is shown to roof cladding, at line 20, in the form
20FS-10d. When asked about this link, Mr Whitaker
stated that the logic link was erroneous because the roof cladding work was not
dependent upon the grouting of the steelwork, and the work in fact started one
week before the grouting of the steelwork.
On Mr Lowe's programme roof cladding is shown starting on
accordingly appears that a number of errors exist in Mr Lowe's programme;
these were largely accepted by him. In my opinion that inevitably makes his
as-built critical path analysis of very doubtful value.
style='mso-spacerun:yes'> It is in my opinion clear that such a
programme is critically dependent upon the logic links between different
activities; that was accepted by both experts.
If that is so, I am of opinion that Mr Whitaker must be correct
when he states that an error in one logic link can vitiate the whole programme,
and errors in a number of links will almost inevitably vitiate the
programme. In this connection, certain
particular parts of Mr Lowe's evidence call for comment. First, in re-examination (day 13, 2.32) Mr Lowe
was asked about the link between line 17 and line 57 (paragraph (xi)
above). In cross-examination he had
accepted that the link should have been start-start rather than finish-start,
and accepted that that could render line 17 non-critical. In re-examination Mr Lowe was asked
whether this would alter the critical path from line 57 (decoration) onwards,
and he replied that he could not say that with certainty. He went on to say, however, that this would
not affect the non-criticality of the roof covering. Nevertheless, the important point is that Mr Lowe
did not know where the critical path lay following the decoration works. It is agreed in the parties' joint minute
that the decoration works were completed on
for the pursuers submitted that Mr Lowe's evidence was not dependent upon
the use of the as-built critical path analysis.
He had analyzed the various delaying events and their effect on the
works in the context of the progress that the works had achieved on site at the
relevant time. The as-built critical
path analysis had been used as a separate tool to analyze the project. Counsel submitted that the most that could be
taken from the defenders' criticism of the critical path analysis is that it
could not be relied upon from
 For the foregoing reasons I generally prefer the approach taken by Mr Whitaker. His views, as contained in his second report (No 7/8 of process), appeared to me to the based on the factual evidence. Moreover, his method of proceeding appeared to be based on sound practical experience and on common sense; I also found the logical connections that he drew in discussing programming to be entirely intelligible. So far as Mr Lowe is concerned, I do not think that it is possible to base any reliable conclusions upon his formal critical path analysis, for the reasons discussed above. Other parts of his evidence were of assistance, however, particularly in relation to concurrent causes of delay; I generally accept his evidence on the delaying effect of the lifts and the stair balustrading. I will now turn to the areas in which, according to the defenders, critical delay was caused by instructions issued on of the pursuers. These were the gas venting system, the roof still work and the series of instructions issued following the replacement of RMJM by Keppie.
the original specification of the contract works a gas proof membrane was to be
inserted at foundation level to prevent the emission of radon gas from the soil
under the building. The form of membrane
originally specified was a product known as Bituthene. On
 It was a matter of agreement between the experts that delays had occurred in the construction of the substructure of the building. The experts were, however, in dispute as to responsibility for that delay. The crucial issue related to the delay in constructing the ground floor slab. Mr Whitaker took the view that this activity was critical (first report, paragraph 2.12), because the reinforced concrete frame of the building was constructed on that slab and was accordingly dependent upon it. Mr Cornish's evidence was to similar effect. I have no difficulty in accepting that evidence. In his second report Mr Whitaker expressed the opinion (paragraphs 2.6-2.10) that the delay had been caused by additional work involved in the alternative gas venting scheme. The ground floor slab, made of concrete, was reinforced by concrete beams. In the tender scheme a straightforward membrane was laid on top of the hardcore which supported the ground beams and ground floor slab; the membrane was continuous, and passed under both beams and slab. In that situation, in Mr Whitaker's opinion, it is common practice to pour the ground beams homogeneously with the ground floor slab. That obviously involves a single pour. The as-built records, however, disclosed that part of the ground beams was constructed first, before the floor slab was constructed above them. Mr Whitaker was of opinion that that resulted from the revised scheme. In the revised scheme using the Proofex membrane, it was necessary to construct polythene pipes through the ground beams to allow gas to pass out of the building. Those pipes involved a more complex form of construction. style='mso-spacerun:yes'> The membrane required to be cut to allow each pipe to pass through it, and a product known as Cordex Ventform was used around the pipes; the arrangement is shown in drawing 1056(28)006D (No 6/138 of process). Mr Whitaker described the work involved as "intricate". He stated that that work, including the separate construction of the ground floor beams to allow the pipes to pass through them and through the membrane, would have the effect of delaying the pouring of the ground floor slab and would thus delay the start of the superstructure works. At paragraph 2.6 of his second report Mr Whitaker produced a chart showing the planned and as-built programmes for the substructure works and the first part of the superstructure works, namely the construction of columns and walls to the first floor. This showed delay to commencement of the columns and walls to first floor of 3 1/2 weeks. The actual duration of that work was three weeks and two days, compared with five weeks planned; consequently the delay to the completion of the activity was only two weeks and one day. Mr Whitaker expressed the opinion that the most likely cause of the delay of 3 1/2 weeks to the start of superstructure works was the additional work instructed in connection with the gas venting scheme.
 In evidence Mr Whitaker stated that the introduction of the gas venting scheme had the direct effect of delaying the pouring of the first half of the ground floor slab (day 10, 2.35). Mr Lowe expressed the view that the ground beams and ground floor slab could have been poured together despite the gas venting scheme; Mr Whitaker stated that such a course would have risked damaging the gas membrane. Mr Whitaker's reason was that the venting pipes would have been relatively unsupported when the concrete was poured, and the connections at the ends of the pipes were delicate and would easily be damaged. If those connections had been disturbed, gas could permeate through the barrier that the membrane was designed to create and enter the building; that would destroy the basic purpose of the gas venting scheme. In cross-examination (day 15, 12.55) it was suggested to Mr Whitaker that the delay was actually caused by extra work required in the lift pit area in the middle of the building; on that basis the defenders should have poured the ground floor slab in three porous rather than two. Mr Whitaker rejected this suggestion; he thought that the fact that the pour was not done in three sections was a further indication that the cause of the delay was the work on the gas venting scheme. In response to questioning by the court (day 19, 12.15) Mr Whitaker stated that the extra work required in the area of the lift pit was completed at about the same time as the additional work required through the introduction of the gas venting scheme; thus pouring the slab in three pours would not have assisted.
 Mr Lowe
(day 24, 12.07) described the work involved in installing the membranes and
pipes. The defenders required to cut a
hole through the membrane, slide the pipe through the hole, slide the first
part of the membrane collar on to the pipe and attach it, slide on the second
part of the collar and attach it, insert the Ventform
barrier material around the pipe, fill any voids with mortar, and wrap the
membrane over the Ventform.
style='mso-spacerun:yes'> In my opinion that is plainly a relatively
elaborate procedure, and it is one that would not have been required if
construction had proceeded according to the tender drawings. Mr Dibben
stated (day 9, 10.40) that the requirement of gas venting introduced new work
into the contract on the critical path. The
construction of the building was complex on the ground, and the structural
elements were interrelated. Thus the
additional work immediately stopped operations that were occurring; the
defenders had to put the venting in before going on. That was summed up in a letter to the architect
wrote to the defenders by letter dated
"Based upon the information provided by you in your letters of 25 August 1998 and 31 March 1998, the Architect's Instruction issued to you and our projects records, we estimate the effect on the Contract Completion Date to be as follows:
1. Compliance with Architect's Instruction
No. 1 of
2. The Relevant Event caused delay to the works for a period of 2 weeks in the timing of the achievement of the critical first floor slab consequent upon the revised erection sequence of the lower structure".
The letter continued by stating that
RMJM had been advised that, by direct agreement with the pursuers, the
defenders had undertaken to absorb this delay; the result was that the architect
decided that no extension of time should be granted. I should state that no evidence was led
before the court to suggest that any agreement to absorb such delay had been
concluded. The pursuers aver that such
an undertaking had been given by Mr Dibben at a
meeting held on
 Mr Lowe expressed the opinion that the delay in starting the superstructure was caused by the defenders' decision to revise their original construction sequence (day 24, 12.29). He was not clear why the revised sequence had been adopted. His position seems inconsistent with that of RMJM, who were the contract architect at the relevant time. On this matter, I am of opinion that, if any substantial criticism of the defenders' decision were possible, it would in all probability have been taken up by RMJM. The fact that it was not indicates that the decision is likely to have been reasonable.
 Mr Lowe
further gave evidence that the delay in the construction of the ground floor
slab resulted from problems that were encountered with out of position
piles. This necessitated the redesign of
the pile caps at gridlines A3, A4, A12 and D3.
The ground floor slab was in fact poured in two halves, and three of the
piles in question, A3, A4 and D3, were in the area of the second pour. Consequently it is unlikely that they delayed
the first pour. It was the first pour that
was critical, however, because that permitted a start to be made on the works
above the ground floor slab. So far as
A12 was concerned, the problem was resolved on
these circumstances I conclude that the only explanation for the delay that has
been advanced is the change in the construction activities necessitated by the
gas venting scheme. No other tenable
alternative has in my opinion been put forward.
My conclusion is supported by the defenders' contemporary claim and by
the reaction of RMJM to that claim.
There was also evidence in the Clerk of Works' diary, in the period from
next issue that must be considered is causation: whether the instruction
relating to the gas venting scheme caused completion of the Works to the
delayed beyond the Completion Date. In
my opinion it is clear that completion of the ground floor slab was a critical
activity, as it formed the base on which the whole superstructure was
constructed. style='mso-spacerun:yes'> That was the view of both Mr Cornish
(day 2, 11.35) and Mr Whitaker (second report, paragraph 2.11); Mr Whitaker
stated that a delay in the ground floor slab would inevitably delay completion
of the Works as a whole unless exceptional measures were taken to recover lost
time. That seems obvious; as Mr Whitaker
explained in his report (at paragraphs 2.9 and 2.10), the delay in the ground
floor slab delayed the construction of columns and walls to the first floor,
which in turn delayed the first floor slab, which in turn delayed columns and
walls to the second floor, and so on. Mr Whitaker's
opinion was that the length of the delay was 3 1/2 weeks (second report,
paragraph 2.10). That is relatively
close to the figure put forward in the defenders' letter to RMJM of
his second report, Mr Whitaker expressed the view (at paragraphs
2.11-2.16, under reference to the table at Page 7/8/10) that the defenders
recovered some of the time lost through the gas venting instruction; he thought
that by 17 June 1998 the defenders were between 1 1/2 and 2 weeks behind
programme, and were recovering lost time.
Mr Lowe accepted that the defenders had recovered some lost
time. Both experts agreed that at the
finish of the fifth floor slab one week of the initial delay of three weeks
four days had been recovered, reducing the delay to two weeks four days. Both experts also agreed that the sixth floor
slab finished four weeks late. Mr Cornish
(day 2, 12.04 onwards) stated that the defenders had worked longer hours and at
weekends to make up lost time as the superstructure proceeded; they had also
used additional resources. At that time
the defenders were intent on making up the time that had been lost. That had been expensive, however, and there
was no point in continuing to take exceptional measures if that became a
pointless exercise. Eventually it became
apparent that the project would be delayed by the problems with the roof
steelwork, which lay on the critical path.
At that stage it no longer seemed necessary to go to extraordinary
lengths to recover the situation, since that would have no effect on the critical
path of the project (day 3, 11.11). At
that point the defenders had stopped Sunday working and the working of longer
hours, because of the cost. Once the
project had been delayed by the roof steelwork, any such expenditure would be a
pointless exercise. That evidence is
supported by the summary that Mr Cornish made as project manager for the
site meeting held on
 I have found the evidence of Mr Whitaker to be persuasive generally. His opinion was that the instruction of the gas venting scheme caused delay to completion of the Works by 3 1/2 weeks. I am of opinion that that is supported by the evidence summarized above; I accordingly conclude that the gas venting scheme caused delay to completion by a period of 3 1/2 weeks.
Roof steelwork and cladding
 When the defenders were invited to tender for the project the roof cladding specification was based on a system known as Stramit Speedeck. This appears from section H31 of the Bills of Quantities (No 6/28 of process). The Stramit system was an aluminium profiled cladding system. Section H31 began as follows:
"To be read with Preliminaries/General conditions.
The Contractor is invited to offer alternative proposals for this specification. Any alternative must achieve the technical and visual performance inherent in this specification and relating drawings.
In any event the Contractor or specialist will be required to assume full responsibility for the design, construction and warranty of the roof enclosure".
The reference in that provision to alternative proposals is an invitation to the contractor to provide Value Engineering ("VE") proposals in relation to specified parts of the Works. The intention was that the contractor should put forward alternative systems of construction which would produce cost savings; these would obviously be reflected in the Contract Sum. In the course of the tendering process the defenders put forward a list of such proposals (No 7/17 of process); these included the system of roof covering, where a proposal was made to use a built up roof covering system rather than the proprietary Stramit system. The proposal relating to the roof covering system was VE Proposal 13; it provided: "Change specification of roof cladding to built-up system". A saving of £5,000 was placed against this item. In total 32 VE proposals were made, which might result in a total saving of £128,000.
Contractual status of VE Proposal 13
first issue that arises between the parties in relation to the roof steelwork
and cladding is the contractual status of VE Proposal 13. The defenders contend that that proposal
formed part of the contract.
Consequently, when on
 Certain clauses of the parties' contract are relevant to this issue. The most significant of these is clause 14, headed "Contract Sum". This clause forms part of the Schedule of Amendments specially prepared for the purposes of the parties' contract; it replaces clauses 14.1 and 14.2 of the JCT Standard Form. Its purpose is, broadly speaking, to replace the usual JCT clause with a provision specifying a guaranteed maximum sum and taking account of Value Engineering savings. Clause 14.1 provides as follows:
"The Employer shall pay to the Contractor in consideration of the carrying out and completion of the Works the guaranteed maximum price comprising, the Contract Sum or such other sum as shall become payable hereunder at the time and in the manner specified in the Conditions".
Clause 14.2 indicates the significance of the guaranteed maximum price:
"Notwithstanding anything contained in the Contract whether express or implied and/or any claim at law the Employer's entire aggregate liability for any payment to the Contractor of any sum of whatsoever in nature and howsoever arising for the carrying out and completion of the Works shall be limited to and in no circumstances exceed the guaranteed maximum price comprised in the Contract Sum save only where the Conditions expressly provide for any increase in the Contract Sum".
Clause 14.3 then provides:
"The quantity and quality of work included in the Contract Sum shall be deemed to be that which is required to be carried out and completed in compliance with the Contract Documents".
That indicates a clear relationship between the work that is to be carried out under the Contract and the Contract Sum; I consider this relationship to be important for reasons that are discussed further below. Clause 14.5 provides for adjustment of the Guaranteed Maximum Price Contract Sum in respect of three matters: provisional sums; contingencies and day work; and unforeseen or unknown ground conditions. No mention is made there of Value Engineering savings. Clause 14.6 indicates the amount of the guaranteed maximum price:
"The Guaranteed Maximum Price Contract Sum is £4,959,578 comprising all adjustments made for Value Engineering savings and the like and is as set out in Appendix E hereto".
Clause 14.7 deals with VE savings; it provides:
"The Value Engineering savings which form part of the Contract Sum are defined and set out in Appendix F hereto".
Finally, clause 14.8 provides that any Value Engineering savings other than those stipulated in clause 14.7 are to be shared between the parties in an agreed manner.
 VE proposal 13 is specified in Appendix F as follows:
"Omit stramit roofing as described in specification Clause H31:140 and substitute with a built up roof cladding system as follows: --
· Topsheet in plastisol coated steel outer sheet.
· Breather membrane.
· Fibre glass quilt insulation 100 mm thick.
· White enamel faced under liner sheet with taped joints fixed with spacers to purlins.
Roof pitch will need to be a minimum of 6°".
The saving brought out in respect of the proposal is £5,000.
E sets out the calculation of the Guaranteed Maximum Price Contract Sum. The calculation proceeds as follows. It starts with the original tender sum of
£4,919,912. To that is added a
Guaranteed Maximum Price "premium" of £76,000. Three deductions are then made: current VE
savings amounting to £128,000; a saving of £100,000 if a
 It is in my opinion clear from the foregoing provisions of the Contract that the Contract Sum is calculated on the basis that the VE proposals set out in Appendix E form part of the Works. That is clear from clause 14.6, where it is expressly stated that the Contract Sum includes all adjustments made for VE savings as set out in Appendix E, and from Appendix E itself, where the calculation shows the deduction made for VE savings. At this point it is important to bear in mind the nature of the present contract; it involves the provision of goods and services in consideration for a price, and generally speaking the work that is to be provided under the contract will be reflected in that price. This is a matter of great importance to the parties, because these matters will determine the economic benefits that they obtain from the contract. It is, moreover, a factor that is directly reflected in the terms of clause 14.3. It follows that if an item of work is included in the Contract Sum it will normally form part of the contractual Works. In the present case, therefore, I am of opinion that the Works included the built up system of roof covering indicated in VE Proposal 13. This conclusion is supported by a practical consideration: if the VE proposals were not included in the Works, the Contract Sum would have to be recalculated to reflect the defenders' obligations as contractor. That would introduce an unnecessary complexity; if the Works did not include the VE proposals, it would plainly make sense to calculate the Contract Sum on that basis.
 Three other provisions of the contract support the conclusion that the VE proposals form part of the Works. First, if the Works did not include the VE proposals, it is difficult to see the point of clauses 14.6 and 14.7, both of which refer expressly to VE savings; clause 14 as a whole could have assumed a simpler form, as could the calculations in Appendix.E. Secondly, clause 14.5 provides expressly for certain forms of adjustment. If the VE proposals contained in Appendix E did not form part of the Works, it would be expected that they would be referred to in that clause, either as provisional sums or in an analogous manner. That was not done, however. Thirdly, clause 14.8 makes express provision for VE savings other than those contained in Appendix E. That indicates that a clear distinction is drawn in the contract between the Appendix E savings and other possible savings, with the former being included in the Contract Sum and Works and the latter being the subject of further adjustment.
the pursuers it was contended that the contract specification provided for the
use of the Stramit system. The Bills of Quantities (No 6/28 of process)
provided at Bill 3, page 3/21-22, for metal profiled roof cladding, for which
the contractor or specialist subcontractor was to assume full design
responsibility, thus making it contractor design work. The contractor was invited to submit
alternative proposals; such an alternative proposal was embodied in VE Proposal
13. The pursuers' submission was that
the VE Proposals were not incorporated into the contract; only the terms of the
specification and Bills were so incorporated.
The VE Proposals could be accepted or rejected by the architect, but
only following the submission of detailed proposals by the contractor. The relevant procedures had been agreed
between the architect and the defenders at a site meeting held on
 The difficulty with the foregoing argument is twofold: it fails to give effect to the manner in which the Contract Sum is calculated, and it fails to give content to the provisions of clause 14, read together with Appendices E and F. In the first place, it is clear from clause 14.6, read together with Appendix E, that the Contract Sum is calculated on the basis that all of the VE Proposals are included in the Works. That is plain from the terms of Appendix E, and also from clause 14.6 itself, which states that the Contract Sum comprises all adjustments made for Value Engineering savings. Clause 14.7 then states that the Value Engineering savings which form part of the Contract Sum are set out in Appendix F; these include VE Proposal 13. The Contract Sum is, obviously, the consideration for the Works at the time when the contract was concluded, and it is implicit in the notion of consideration that the elements that are included in the calculation of the Contract Sum will form part of the parties' contract. In the second place, if the pursuers' argument on this point is correct, it is difficult to see the point of clause 14.6 and .7. These sub-clauses deal with the VE savings in a specific manner, which is quite distinct from the treatment of provisional sums in clause 14.5. If the VE Proposals were not part of the Works agreed on in the Contract, it would have made sense to deal with them in the same way as provisional sums, with a subsequent adjustment to the Contract Sum if a VE Proposal were taken up. The incompatibility of the pursuers' argument with the structure of clause 14 is further strengthened by the provisions of clause 14.8, which deals with VE savings other than those stipulated in clause 14.7 should be dealt with distinctly. That is an indication that the clause 14.7 VE Proposals were part of the Works, unlike any other VE Proposals, which would be dealt with by an adjustment to the Contract Sum.
 The pursuers' argument on this topic proceeded on the premise that the VE Proposals in Appendix F were "optional", in the sense that the architect still had to decide whether to adopt them. In support of this argument reference was made to the terms of the VE Proposals; it was said that the proposals were fluid in nature, and were presented in outline form. It is true that the VE Proposals were optional, but I am of opinion that this factor is neutral in deciding whether the VE Proposals were part of the Works. The "option" in relation to the VE Proposals can be regarded as a power to adopt or a power to reject; if the option is construed as a power to reject its existence is wholly compatible with the proposition that the Appendix F VE Proposals formed part of the Works. The outline nature of the proposals themselves is not I think a decisive factor; the proposals had clearly been considered by the defenders, and sufficient description was given that the architect knew broadly what was proposed in each case. The option to accept or reject the proposals could only be exercised at a later stage, when more detail was available. At that stage, if the VE Proposals were part of the contract, a decision to reject would be a variation; if they were not part of the contract, a decision to accept would be a variation. style='mso-spacerun:yes'> This factor accordingly seems to me to be neutral.
 The pursuers further referred to the manner in which the Guaranteed Maximum Price Contract Sum was calculated in Appendix E. They submitted that the contractor had arrived at the most competitive price for the Works by pricing on the basis that the VE savings that it proposed to make would be achieved. This was described as a "business gamble" taken by the contractor, and it was suggested that it was presumably one of the reasons why a sizeable "Guaranteed Maximum Price premium" had been added to the Contract Sum. The fact that the VE savings were included in the final Guaranteed Maximum Price did not incorporate them into the contract; it rather placed an onus upon the contractor to ensure that as many as possible of its VE proposals were accepted by the employer in order to maximize the contractor's own profit.
 It is no doubt correct to suggest that the contractor had arrived at its most competitive price by taking the VE savings into account; reduction in the price was the obvious purpose of the VE Proposals. It is also correct to state that a "business gamble" is involved, but that is true of any tender. The Guaranteed Maximum Price premium seems to me to the just that: the contractor agreed to a cap on the price for the Works, subject to certain defined exceptions, but took a premium in exchange. The VE savings were taken into account in determining the Guaranteed Maximum Price, but that merely emphasizes the point made above: the savings were reflected in the calculation of the total Contract Sum, with all the consequences that that entails. That seems to me to point to the proposition that the VE Proposals were included in the contract Works. As to the suggestion that the VE proposals were designed to maximize the contractor's profit, it appears to me that they were designed essentially to reduce the tender price; whether this resulted in a greater profit would depend upon a range of factors as the contract proceeded. If the VE Proposals formed part of the parties' contract, any rejection of a proposal would amount to a variation, with a potential impact on the total amount payable by the employer, and also a potential impact on the contractor's profit. That it cannot be said that that was any "onus" on the contractor to have VE Proposals accepted; they might or might not increase its profit, although they would certainly make its tender price more competitive.
 The pursuers further submitted that the defenders' argument was incompatible with clause 1 of the Scottish Building Contract. That clause provides that "the Contractor shall carry out the Works (as defined in Appendix 1 hereto) in accordance with the Drawings numbered as per the Schedule annexed to this Contract; the Schedule of Amendments to the Building Contract and the Bills of Quantities all as annexed and signed as relative hereto". The definition of "Works" in Appendix 1 refers to "The Contract Works shown and described in the Contract Drawings and in the Contract Bills and including any changes made to these in accordance with this Contract". No reference was made in these provisions to any link between the extent of the Works and the Contract Sum. In my opinion the fact that no express reference is made to any such link in the provisions cited by the pursuers is not significant. The link exists nevertheless; the Contract Sum is paid in consideration of the performance of the Works, and that very elementary connection creates a link. This conclusion is not altered by the terms of the Contract. Moreover, I am of opinion that reliance on the Bills of Quantities is not helpful. Clause 2.2.1 of the JCT Standard Form provides that nothing in the Contract Bills should override or modify the application of the Building Contract, the Conditions for the Appendix. The basic contractual provisions thus override the Bills. This analysis is further supported by clause 14.4 of the parties' contract, which states that the Bill of Quantities is for guidance only.
 The pursuers argued that the roofing work was Performance Specified Work. Performance Specified Work is identified on page 28 of the parties' version of the Scottish Building Contract (No 6/1 of process); the list includes Roofing Work, with a reference to Bill H33; this is in fact a misprint for Bill H31. Bill H31 deals with the roof cladding but not the roof steelwork. Clause 18.104.22.168 provides that Performance Specified Work should accord with any relevant specification in the Contract Documents; the Contract Documents are defined in Appendix 1 to the Scottish Building Contract as "The Contract Drawings, the Contract Bills, the Conditions, this Appendix and the Appendix II to the Building Contract". Consequently, as I understood the pursuers' submissions, the system of roof cladding must be that provided for in the contract documents rather than the defenders' VE Proposals. They relied in particular on the provisions of Bill H31, which indicates what is required by way of roof cladding, under reference to the Stramit system.
 Whether or not the roof cladding was properly defined in the contract as Performance Specified Work, I do not think that that has any bearing on the question that is crucial for present purposes, namely whether the parties' contract specified VE Proposal 13 or the Stramit system set out in the Bill H33. If VE Proposal 13 was included in the contract, it would override the Bills, in accordance with clause 2.2.1 of the JCT Form. In any event, when the contractor puts forward a VE Proposal, it is obvious that he is putting forward an alternative to the architect's proposals, and that that alternative is one that may or may not be accepted. In that event, the proper interpretation is in my opinion that the contractor's proposal, when duly accepted by the architect, will supersede the criteria for Performance Specified Work to the extent that it is inconsistent with those criteria. That seems to render categorization as Performance Specified Work irrelevant. In any event, I am of opinion that the pursuers have failed to establish that the roof cladding was Performance Certified Work. Performance Specified Work is defined in clause 42.1; this provides that such work must be work which is identified in the Appendix and is to be provided by the Contractor, and of which certain requirements have been predetermined and are shown on the Contract drawings and in the Contract Bills. "Contract Drawings" are defined in Appendix 1 of the Scottish Supplement as drawings referred to in the Building Contract which have been signed by the employer and the contractor or on their behalf. In the present case no such drawings were produced. It is the pursuers who assert that the roof cladding was Performance Specified Work; consequently any failure to produce drawings must in my view mean that it has not been proved that the roof cladding fell into the category of Performance Specified Work.
to their submission that the roof covering was Performance Specified Work, the
pursuers submitted that the defenders were in default, in that they had failed
to carry through the various procedures required in respect of such work. In this connection, the pursuers relied on
certain provisions of clause 2 of the contract conditions. Clause 2.4.4 of the contract conditions (a
clause forming part of the special conditions) places an obligation on the contractor
to provide the architect with all information necessary for Performance
Specified Work. Clauses 2.5.1 and 2.5.2
state that the contractor is to provide the architect with drawings,
specifications and details in respect of such work, in sufficient time for the architect
to comment on such work in line with the contractor's programme. Clause 2.7 provides that no extension of time
should be granted to the extent that there is any failure by the contractor to
provide such drawings and the like. The
procedures for use in respect of the VE Proposals were agreed at a site meeting
this part of the argument the pursuers ran together provisions that related
specifically to Performance Specified Work and the procedures that were agreed
for dealing with VE Proposals. If I am
correct that the roof cladding was not Performance Specified Work, the
provisions relating to such work are not relevant. I think that the argument can be advanced,
however, on the restricted basis that the VE procedures were not followed by
the defenders (see No 7/351 of process, page 9). It is true that the VE
procedures set out in the minutes of the site meeting of
History of instructions relating to the roof steelwork and cladding
receipt of the drawing 1056(26)003, the defenders passed it to their steelwork
fabrication subcontractor, Zonner Industries
response to Zonner's fax, RMJM acting in their
capacity as structural engineer sent the defenders a fax dated
fact no instructions were issued by the architect during the course of the
following week. On
"VE Item No 13 - Change roof cladding specification to a built up system.
Agreed. SCL [the defenders] to confirm that it does not affect the lightning protection. SCL to pick up any changes in the roof pitch on the fabricators drawings".
Mr Dibben stated that, as recorded in the minutes, it was agreed that the defenders should proceed with VE Proposal 13. Mr Cornish also stated in evidence that that was his understanding of the position (day 2, 3.16). In the minutes no indication is given that any further details or proposals were required from the defenders in respect of VE Proposal 13; on the basis of the terms of the minutes and Mr Dibben's evidence, I conclude that at the VE meeting it was decided that the Proposal 13 was to go ahead. The minute further states, at paragraph 3.0, that RMJM were to issue Architect's Instructions as appropriate to cover all of the items discussed.
further meeting at which certain VE Proposals were discussed was held on
"I have recommended to First Stop Hotels [the pursuers] that we retain the use of speedeck to the main roof. I will advise you of an instruction as soon as I can".
In relation to that letter, Mr Cornish commented (day 2, 3.32) stated that his reaction was "exasperation". He stated that the situation was that the defenders had no direction as to which way to go, because RMJM had not made their mind up. The next communication from RMJM to the defenders was a fax dated 29 June (No 7/26 of process). This stated
"I confirm my telephone call of Friday 26 June advising that First Stop Hotels have agreed that the roof specification as currently instructed (Stramit Speedeck) is not to be replaced by any alternative".
defenders wrote (No 7/27 of process) on the same date to their roofing subcontractor,
Kelsey Roofing Industries Ltd, to confirm that it was the defenders' firm
intention to enter into a subcontract with them for the roofing works. The letter went on to state that the
specification would be as discussed at a meeting of 17 June, and that the architect
had confirmed that the Speedeck roof option was to be
adopted. Mr Cornish indicated that no order had been placed with Kelsey
because that would depend upon the outcome of RMJM's
decision (day 2, 3.50); a subcontract had been concluded with Kelsey as soon as
the defenders knew what was to be built.
Mr Cornish was then asked whether he was satisfied that the regular
progress of the pursuers' works was affected by this. Mr Cornish replied in the affirmative,
and stated that all of the activities concerned were on the critical path. At this stage he had realized that it was
impossible to get the steel and cladding in time, and he was satisfied that
this factor affected critical activities.
Mr Cornish returned to this matter in re-examination (day 8,
3.18). He stated that meetings had been
arranged with Kelsey and Zonner, at which issues had
been raised regarding purlin spacings;
the defenders were pursuing RMJM to clarify structural details. Those details were needed by Kelsey and Zonner for their shop drawings. Load calculations were also needed from
RMJM. The purlin
fixings had in fact been raised by Zonner in their
fax of 13 May. In a subsequent fax of 15
May (No 6/354 of process) RMJM had indicated that the purlin
detail would be changed. The relevant
drawing (1056(26)003, revision A) was nevertheless issued to the defenders on
connection loads were provided by RMJM in a fax dated 13 July (No 7/32 of
process), and certain further details were provided in a fax from RMJM dated 17
July (No 7/34 of process). In relation
to these documents, Mr Cornish stated in evidence (day 8, 3.23) that it
was following the revisions of drawings at this time that Zonner
had everything that they needed. The
final version of the drawings, referred to in the fax of 17 July, indicated
co-ordination between the steelwork (Zonner's
responsibility) and the roofing work (Kelsey's responsibility); the further
detail provided at this stage was essential for the shop drawings. That evidence was not contradicted and I
accept it. I accordingly conclude that
the defenders' subcontractors were not in a position to prepare shop drawings
to enable fabrication to take place until after they received the information
provided with RMJM's fax of 17 July. On 20 July the defenders passed a copy of RMJM's fax of 17 July to Zonner
and Kelsey (No 7/33 of process); in that fax it was indicated that the relevant
drawings would follow as soon as they were received by the defenders. Kelsey responded to that fax by letter dated
Application of clause 25 to roof of steelwork and cladding
 Clause 25 is set out at paragraph  above. The defenders' claim for an extension in respect of roof steelwork and cladding is made on the basis that there occurred a Relevant Event of the sort specified in clause 22.214.171.124. In short, it is contended that the architect, RMJM, failed to provide the necessary instructions to the defenders in due time; there were the instructions to use the Stramit system rather than the VE proposal that was included in the contract (see paragraph  above). To establish such a claim the defenders must show, first, that they made a specific application in writing to the architect for such instructions; secondly, that such application was made on a date which having regard to the Completion Date was neither unreasonably distant from not unreasonably close to the date on which information was required; and thirdly that they did not receive the necessary instruction in due time.
defenders' original construction programme indicated that roof steelwork was to
start on about 27 July 1998 (No
defenders' application for information relating to the steelwork was contained
in an Information Required Schedule (No 7/114 of process), with an accompanying
Package Procurement Schedule. This
Schedule was dated
Mr Whitaker nor Mr Cornish maintained that full information relating
to roof steelwork should have been available by 8 April, the date in the
Package Procurement Schedule; both favoured a date of approximately 11
May. I accept their evidence on this
matter; I consider that such a date would have been reasonable in all the
circumstances. In this respect I rely in
particular on the evidence relating to the lead-in period required for
steelwork; 10 weeks was reasonable for this purpose. On this basis I conclude that the defenders
did not receive the necessary instructions from the architect in due time. The architect's instruction relating to the
roof cladding system that was to be adopted was only received on
Consequences of late instruction
was delivered to the site on
 Mr Whitaker expressed the view (report No 7/8 of process, paragraphs 2.17, 2.41) that the roof steelwork and roof coverings were critical to the completion of the works. He gave two reasons for this conclusion. First, the roof coverings provided a partial weather tight state so that fitting-out of the building could progress. Secondly, the roof coverings formed the plant room, where all the service plant and equipment was housed and to which all of the pipework and electrical and communications cables were connected. Mr Whitaker stated (first report, No 7/1 5/6 of process, paragraph 2.12; in evidence, day 10, 12.12 onwards) that the erection of roof steelwork was a critical milestone in the project; any delay in the steelwork would result in delay to completion of the Works as a whole. The ability to construct the roof cladding was directly dependent upon the roof steelwork, and the cladding enclosed the plant room, which was of major significance in a highly serviced building. Mr Cornish agreed that direction of the roof steelwork was a critical activity, for broadly similar reasons to those given by Mr Whitaker (day 2, 11.20 and 11.41).
 Mr Lowe
expressed a contrary view. style='mso-spacerun:yes'> He was of
opinion that the roof steelwork and coverings were not on the critical path,
and thus could not have caused delay to completion of the Works. The reason for this view was that, at the
instigation of Mr Cornish, temporary weatherproofing had been installed at
fourth floor level and then, as construction proceeded, at sixth floor level
(day 3, 11.44). In their Project
Manager's Summary for August 1998 the defenders advised the architect that they
intended to use temporary sheeting at sixth floor level to allow first fix
services to proceed on the fourth and fifth floors by 1 September (No 7/3 of
process). Thus adequate weatherproofing
had been installed to enable mechanical and electrical works to proceed at
lower levels. Those works hand started
this matter, I prefer the views of Mr Whitaker, as supported by Mr Cornish. It is clear that the hotel was a heavily
serviced building. The mechanical and
electrical plant was situated in the roof space; consequently the provision of
a roof covering was critical to the installation of that plant, which was
obviously highly susceptible to wet conditions.
This is made clear by photographs that were spoken to in evidence; in a
photograph at sixth floor level taken on
 In his report (No 6/351 of process, page 1, at paragraph 1.7) Mr Lowe advanced a number of arguments which, he said, led to the conclusion that the defenders could not have proceed with the steelwork any earlier than they actually did.
1. Mr Lowe relied first on the fact that the fire escape stairs above sixth floor level had not been constructed. style='mso-spacerun:yes'> In my opinion this point is not relevant. Mr Whitaker stated that it was obvious that, if the roof steelwork had been available any earlier, the concrete stairs could easily have been finished (day 13, 2.10). Mr Cornish gave evidence that the fire escape stairs were built off the critical path (day 5, 10.52). Moreover, in cross-examination (day 25, 11.16), Mr Lowe accepted that, if the stairs had not been completed, the defenders could have started the steelwork in a different area and come back to the area immediately adjacent to the fire escape stairs at the end. For these reasons I do not think that this point is established.
2. Mr Lowe further relied on the construction of the lift shaft above sixth floor level, which was not completed until August. Mr Cornish gave evidence that, if there had been a problem with this matter, he would have ensured that propping was used to take the load from the steelwork, so that the lift pit could be cast at a later date (day 5, 10.55). Mr Whitaker agreed with that suggestion (day 13, 2.23). Mr Lowe disagreed with these views. style='mso-spacerun:yes'> On this matter I prefer Mr Cornish, who was actually on site at the material time, and Mr Whitaker. I accordingly conclude that this point is not established.
3. Mr Lowe relied on the fact that
the upstand walls around the perimeter of the sixth
floor had not been constructed; these were required to bear the weight of the
structural steel in the roof. Mr Lowe relied in particular on the fact
that the upstand walls had not been completed until
4. The fourth point made by Mr Lowe was that the roof steelwork could not start earlier because falsework and formwork used in constructing the sixth floor slab required to be removed from beneath the sixth floor. Mr Whitaker's view was that it was not necessary to remove the falsework and formwork from below sixth floor level to allow steel erection at that level (day 13, 2.34). Mr Cornish (day 3, 12.20) stated that the erection of steelwork could have proceed despite the falsework and formwork below sixth floor level. The falsework and formwork could have been removed in three ways; the tables could have been stripped in situ at fifth floor level; the tables could have been removed from the building by crane to Church Street, a nearby street, and dismantled there; or the tables could have been removed intact, placed on a flat bed lorry and driven to a remote part of the site for dismantling. In my opinion it is clear that the existence of the falsework and formwork at fifth floor level would not have prevented the construction of the steelwork. I further conclude that it could have been removed using one or other of the methods described by Mr Cornish.
5. Mr Lowe's fifth point was that the roof space at sixth floor level was used by the reinforced concrete subcontractor, E P Rothwell & Sons, to strip formwork and formwork tables until the steel arrived on site. Mr Cornish gave evidence that Rothwell simply took advantage of the roof space because it was known that the steel would not be available until a later date (day 3, 12.16). He further stated that, if it had been necessary, the falsework and formwork could have been dismantled in any of the three ways described in paragraph 4 above. Mr Whitaker's evidence was broadly in agreement with Mr Cornish. I accept Mr Cornish's evidence on this matter, and I conclude that this point is not established.
6. The sixth argument relied on by Mr Lowe was that, for the steel erectors to start work, it was necessary that an access scaffold should be constructed to provide a safe system of working for them; this would include a cantilever for the roof overhang. Mr Cornish gave evidence that the access scaffold was built for the cladding contractor (day 5, 11.04), and in particular to enable the construction of louvres. The steel erectors were permitted to use it, but it was not for their benefit. Without it, they could have proceeded with steel erection using harnesses, lanyards or roof mounted cherry pickers; that would have been a safe method of working. Mr Whitaker agreed with that evidence (day 13, 2.40). Mr Lowe disagreed with the position taken by Mr Cornish. He accepted, however, that cherry pickers could be used if they could be put in place (day 25, 12.15). On this .I prefer the evidence of Mr Cornish and Mr Whitaker. Mr Cornish was on site at the relevant time, and I find that he gave his evidence by reference to the actual conditions that he experienced. I am satisfied that one of the methods that he suggested could have been used without difficulty.
7. Mr Lowe's final point related to the provision of suitable cranage for the steel erection. Mr Lowe suggested that the tower crane on site could not service both the concrete walls at roof level and the steelwork at the same level. Mr Cornish gave evidence that the steel erectors would have been given preference over any other trades; in any event the crane could have been used before or after (day 5, 11.07). In addition, Mr Lowe (day 25, 12.43) accepted that a concrete pump could have been used for the concreting works. On this matter I accept the evidence of Mr Cornish, and I find that the point has not been established
 For the reasons stated above, in particular at paragraphs  and , I am of opinion that the Works were delayed due to the late instructions given by the architect in respect of the roof steelwork. That entitles the defenders to an extension of time, and the next question is how long that extension should be. Mr Whitaker dealt with this matter in his report No 7/8 of process, at paragraph 2.48:
"Having carefully considered all of the above facts, I am of the opinion that the roof steelwork and the roof cladding were critical to the completion of the Works. I am further of the opinion that these critical tasks commenced 5 weeks later than planned and that being critical tasks this caused a five week delay to completion of the whole of the Works".
Mr Whitaker developed this matter at paragraph
2.53. He was of opinion that the
defenders were delayed in the completion of the Works until
Instructions following replacement of RMJM by Keppie
the roof cladding had been put in place Mr Whitaker's evidence was that
work on the project became much more intensive (No 7/8 of process, paragraph
2.54). His view was based on the
defenders' daily diary and report sheets and the Clerk of Works' diary. Both the defenders and the Clerk of Works, Mr
Foley, reported at meetings that the Works were proceeding approximately 5
weeks late. On
"[The defenders] noted the [pursuers'] change to the Design Team and felt that their concerns at his change so late in the contract should be recorded. They would of course do their best to assist the new design team members".
In his evidence Mr Cornish stated that he wanted the defenders' concerns to be recorded because a lot of unresolved issues existed and a new design team would be coming on to the project without any initial knowledge of it; indeed they did not even have the project drawings and documentation (day 3, 1.51 onwards). Mr Cornish added that it was obvious at that site meeting that the new design team knew nothing about the job; they had asked the defenders to photocopy all the documentation and courier it to them; the defenders did that. Neither Mr Cornish nor Mr Whitaker had ever encountered such a situation previously in their careers. At the site meeting held on 2 December the defenders stated that they continued to be 5 1/2 weeks behind programme and had issued a 57-week target programme. Mr Foley agreed that the Works were 5 1/2-6 weeks behind programme.
defenders contend that, following the change of design team, a substantial
number of items were instructed late.
These, it is said, had an effect on the completion of the contract
Works, and constituted Relevant Events for the purposes of clause 25. The defenders' contention was first advanced
at site meeting No 13, held on
1. Final fix items to en suites
Works did not originally include the installation of fittings into the shower
rooms attached to the hotel bedrooms (referred to in the documentation as en
suites). At site meeting No 9, held on
roll holder - Anticipated delivery 10
days = due
rack - Anticipated delivery
21 days = due
bar - Anticipated
delivery 21 days = due
hook - Anticipated delivery
10 days = due
style='font:7.0pt "Times New Roman"'>
shelf - Anticipated delivery
10 days = due
vi. style='font:7.0pt "Times New Roman"'> Shaving mirror - No delivery period quoted.
On 22nd January 1998 Architects issued further instructions, these included updated quotations stating that all items except the shaving mirror are subject to a 21 day lead-in period.
mirrors were delivered in good time.
However, all other items were not delivered until
delaying factor was that delivery of items i, iv and v was received 17 days later than quoted by Keppie in their letter of
the delayed deliveries, revised instructions were issued regarding fixing of
the items. Thompson MacLeod confirmed
fixing positions of items ii, iii, iv and v and soap
MacLeod subsequently gave verbal instructions changing heights for the toilet
roll holder on
screws supplied for the shaving mirrors were unsuitable for the locations in
the en-suites. SCL had to order new
security screws for all the shaving mirrors.
These were delivered on
mentioned, fixing of item v (glass shelf) started on
installation of all the available en-suite fittings was completed on
the shelves will be delivered before
Mr Cornish, who was the author of that letter, spoke to its contents (day 3, 3.18). On the basis of his evidence, I am satisfied that the statements of fact in the letter are substantially accurate.
 Mr Cornish
(day 3, 2.46 onwards) explained that the defenders had envisaged finishing
rooms and snagging them on a floor by floor basis; thereafter the rooms would
be locked so that one could gain entry and damage the work that had been
done. Because of the difficulties
mentioned in the letter that was not possible; it was necessary to keep going
back into bedrooms and bathrooms in order to install each successive item as it
arrived. The problems were summarized in
Mr Cornish's project manager's report to the
site meeting held on
 Mr Cornish
gave evidence that a reasonable time for instruction of the en suite fittings
would have been ten weeks prior to the Completion Date (day 3, 3.00) that would
have been in late November 1998. He
explained that that would have enabled the defenders to start the process of
ordering the fittings earlier; they would thus have secured delivery at an
earlier stage. This would have helped
the defenders to complete the rooms systematically, floor by floor, and to lock
rooms once they had been completed. Mr Whitaker's
evidence (report, No 7/8 of process, paragraph 2.70 and accompanying table; day
15, 3.45) was that a reasonable date for issuing the instruction would have
accept the evidence of Mr Whitaker, which was supported by the evidence of
Mr Cornish, that the instruction should have been issued on or about
Pursuers' criticism of defenders' case on instructions following Keppie's appointment
this point it is convenient to deal with certain general criticisms made by the
pursuers of the defenders' arguments relating to instructions given following
the replacement of RMJM by Keppie. These related in particular to the delay
analyses set out by Mr Whitaker in his second report (No 7/8 of
process). First, Mr Lowe criticized
the type of delay analysis carried out by Mr Whitaker as a
"theoretical exercise" (in his report No 6/351 of process, and in
evidence: day 22, 2.35). Mr Whitaker
had stated in evidence that he had carried out a small version of a critical
path analysis in respect of each activity; these were contained in the tables
in his second report. The pursuers
submitted, however, that no practical analysis had been carried out by Mr Whitaker. The en suites were taken as an example: Mr Whitaker's
analysis started from the premise that the reasonable time for issue of the
instruction had to be measured against a Completion Date of
do not think that this criticism is well founded. The method used by Mr Whitaker was as
follows (day 11, 3.36 onwards). He first
established a chronology, based on what actually happened on site in respect of
each of the enumerated items. He then
calculated the time that was reasonably required for delivery, installation and
snagging. In part this calculation was
based on what actually happened, and in part was based on Mr Whitaker's
judgment as to what was reasonable for any particular aspect of the work. I was satisfied that he had great experience
of programming in the construction industry and that his estimates of the
periods required for particular items of work were reasonable. Once Mr Whitaker had calculated the
period required for delivery, installation and snagging he worked backwards
from the contractual completion date (
 The pursuers' second criticism of Mr Whitaker's approach was that, in his delay tables, he used "guesstimates" for the duration of, for example, order, delivery and installation. In fact it is clear from Mr Whitaker's tables that he did take account of what actually happened in determining the duration of any particular activity. Thus, in relation to the fix items in the en suites, he based his analysis on the issue of the relevant instruction on 22 January, the start of installation on 11 February and the end of the installation period on 10 March. All of these were actual dates, a point that was accepted by Mr Lowe in cross-examination (day 26, 10.50). This point applies generally to all of the final fix items. In some cases Mr Whitaker had to estimate the duration of one part of an activity, for example (in the case of the en suite fittings) snagging and the necessary period for ordering the fittings. As indicated in the last paragraph, however, I am satisfied that Mr Whitaker's estimates were reasonable; they were based on his experience in the construction industry, and none of them appeared to me to be exaggerated. The pursuers' third criticism of Mr Whitaker was that he had made excessive allowances for snagging. In relation to the en suite fittings, the pursuers submitted, on the basis of Mr Lowe's evidence (day 22, 2.57) that the contractor should tidy up when he finished working in an area. That was not snagging; snagging involved in dealing with items of work that had been done incorrectly. This difference is, I suspect, more semantic than real. As work proceeds on a task such as installing bathroom fittings, it is obvious that some untidiness will result; it also seems to me to be very likely that some items may not be properly installed, or that tiles or woodwork may be damaged. All of these matters would require to be dealt with, on a room-by-room basis. That is what I understand snagging to amount to. Given the number of rooms involved, I did not find Mr Whitaker's estimates (14 days for fittings in 167 bathrooms) excessive. The pursuers' fourth criticism of Mr Whitaker's approach was that he had not endeavoured to demonstrate that any of the listed items were on the critical path. On the basis of Mr Lowe's evidence, the pursuers submitted that they were not. I have already indicated that I am unable to rely on Mr Lowe's exercise in determining the critical path, at least in the later stages of the contract. In a sense, as a contract nears completion, more items will fall on the critical path because practical completion is impossible until they have been completed. This culminates in the last item to be completed which is, of necessity, on the critical path. In relation to the various items of work that Mr Whitaker thought caused delay to completion as a result of late instructions following the appointment of Keppie, I am satisfied that each of them was on the critical path, in the sense that the work was necessary before a hotel could be said to have achieved practical completion.
the pursuers criticized Mr Whitaker's analysis because he had made use of
the original completion date of
 Finally, the pursuers submitted that the defenders had sought to categorize the various events following the appointment of Keppie as late instructions. The evidence was not to that effect, however; each of these heads of claim amounted to additional work and thus a variation. style='mso-spacerun:yes'> In my opinion there is no incompatibility between a late instruction and a variation. style='mso-spacerun:yes'> A particular instruction may amount to a variation, but it may still be late; that seems elementary. Thus I do not think that the defenders' approach to the items instructed following Keppie's appointment is erroneous on this ground. Indeed, once it became clear that further instructions were likely to be given regarding final fix items in the bedrooms and en suites, Mr Cornish produced the schedule referred to in paragraph  above; this was discussed at the site meeting of 7 October 1998, and was designed to ensure that timeous instructions were given in respect of all of those items. Following the issuing of that document, I am of opinion that the provisions of clause 25 relating to late instructions were applicable.
 Mr Lowe also gave evidence on the effect of the instruction relating to the en suite fittings. He criticized Mr Whitaker's allowance of 14 days for snagging, on the basis that most of what Mr Whitaker described as snagging was merely tidying up. I reject this criticism, for the reasons stated above; it seems to me that the difference is largely semantic, and that some time would be required to ensure that the rooms were in good order following the completion of the installation of the final fix items. Mr Lowe further concluded that this item of work did not fall on the critical path and thus did not delay completion. In my opinion the lateness of the instruction inevitably meant that the completion of this item would fall after the contractual completion date. I am further opinion that this item was critical, in the sense that properly fitted out bathrooms were essential for practical completion of the hotel.
2. Bedhead lighting
bedhead lighting was not part of the Works. At the site meeting held on
are items that cannot be deferred any longer.
Electrically, we cannot of course complete bedrooms without bedhead lights.
The defenders received an Architect's
Instruction in relation to the bedhead lighting on
"The bedhead lights were not part of our contract. However, since the bedhead lights are hard wired it is not possible to bring power into the rooms until the bedhead lights are fitted, nor is it possible to test and commission the electrical services.
received your instruction to supply and fix the bedhead
In site meeting No. 12 (6th January 1999), minute 3.5, Keppie state that the bedhead lights supplier could deliver approx. 50% of the fittings by 20th January 1999 with the balance by 5th February 1999 on early receipt of an order.
SCL placed an
order for the items on
Deliveries were not made in accordance with the date quoted by Keppie. Actual deliveries were received as follows:
The further delaying factor was that:-
a. 36No. were delivered 6 days later than the dates quoted.
b. 134No. were delivered 13 days later than the dates quoted.
c. 170No. were delivered in accordance with the quoted dates".
The Clerk of Works' report for the
 Mr Whitaker
dealt with the bedhead lights in his report (No 7/8
of process) at paragraphs 2.71-2.73, with a table summarizing his position on
 Mr Lowe accepted in cross-examination that the instruction relating to bedhead lighting was issued late (day 26, 12.09). He was not re-examined on that matter. He did, however, state that the late instruction did not cause any delay to completion, on the basis that this lighting did not fall on the critical path. In my opinion this item was critical, in the sense that the proper fitting out of the bedrooms was necessary before practical completion could be said to have taken place.
 In my opinion a written request for an Architect's
Instruction was made in the schedule produced at the site meeting held on
3. Trouser presses
 The supply and installation of trouser presses was not part
of the original contract. At the time of
site meeting No 9, which was held on
"The trouser presses were not part of our contract. However, they are wired in and then covered with a duct from the furniture case goods manufacturer. Consequently, the trouser presses are required in order to finish the furniture installation, power up the rooms and test and commission the electrical works.
Our letter dated 30th November to RMJM confirms that trouser presses need to be delivered floor by floor to our programme.
was confirmed to the client via our fax dated
A sample trouser press was fitted in the mock-up room and the following problems were identified:
a. Cable tidy boxes incorrectly sized.
b. Setting out of trouser press position seemed incorrect and required clarification.
c. Trouser presses were plug in type not hard wired as the client required (the specification was correctly installed with single gang sockets).
problems were witnessed by Janet Matthews [an operations manager for the
pursuers] and communicated to Keppie Architects by
a. Fit cable tidy box and decorate.
b. Setting out position clarified.
c. Remove of all single gang plugs and replace with fused spurs.
delaying factor was that trouser press installation started on
fitting the trouser presses we wrote to yourselves on
The evidence did not disclose
precisely when fitting of the trouser presses was completed, but it is clear
from the letter that this had not occurred by
 Mr Whitaker
dealt with trouser presses in his second report (No 7/8 of process) at
paragraphs 2.78-2.87, and in a table found on page 32. His opinion was that a reasonable date for an
instruction relating to trouser presses would have been
my opinion a written request for information relating to trouser presses was
made in the schedule produced by Mr Cornish at site meeting No 9, held on
7 October 1998, and indeed in the Information Required Schedule of 26 January
1998. It was not suggested that this
application was made on a date unreasonably close to or unreasonably distant
from the date when the information was required. I am accordingly of opinion that the
defenders made a written request for the appropriate instruction in accordance
with clause 25.4.6. I accept the
evidence of Mr Whitaker that an Architect's Instruction should have been
issued in early December 1998. I
therefore consider that the relevant instruction was not issued "in due
time" for the purposes of clause 25.4.6, and that there was accordingly a
Relevant Event within the meaning of that clause. In relation to the criticality of this item, Mr Cornish
stated that the installation of the trouser presses affected the defenders'
ability to complete the fitting out of the bedrooms; electricians, carpenters
and decorators all had to carry out work in relation to the fitting of the
trouser presses. In addition a separate
commissioning exercise was required (day 4, 11.09 onwards). Mr Whitaker stated (in his report No
7/156 of process, and paragraph 2.12) that the bedroom fit out activity was
critical. In my opinion that is
clear. Mr Whitaker further
expressed the opinion (in his second report) that as a result of the late
instruction regarding trouser presses the completion of the Works was delayed
 Mr Lowe
gave evidence that the problems with the trouser presses related to the system
of wiring. He thought that Keppie had dealt with that problem as quickly as possible
(day 26, 12.36 onwards). In addition, Mr Lowe
expressed the view that the instruction in relation to the trouser presses was
issued in good time having regard to the contractor's actual progress on site
(in his report, No 6/351 of process, page 16). In cross-examination (day 26,
12.39) Mr Lowe reiterated that the instruction was not late; although the
issue had been raised by the defenders at the site meeting of 7 October, he
thought that that was only in the context of a "delivery
situation". In my opinion that is
not the correct analysis of the matter raised at that site meeting; while the
trouser presses were raised as a client supply item, Mr Cornish made it
clear that he wanted the precise responsibilities in respect of such items to
be determined as a matter of urgency.
The schedule produced by the defenders at that meeting includes the
comment "Install w/c
4. Central atrium beam encasement
site meeting No 10, held on 4 November 1998, the defenders tendered a monthly
report which contained a list of outstanding information as at that date (No
7/42 of process, page 13). The seventh
item included in that list was "Details of gantry to Central Atrium (if
required)". That item related to a gantry across the atrium of the hotel to
which window cleaning harnesses could be fixed, and the encasement of beams in
the central atrium area with MDF boarding.
The list of outstanding information indicated that all of the items
mentioned were required as a matter of urgency, and not later than
 Mr Whitaker
expressed the opinion that a reasonable time for the issue of the instruction
relating to the gantries would have been
am further of opinion that the issue of this instruction was critical for the
completion of the project. Mr Cornish
(day 4, 11.45) explained by the information was important. The atrium was six storeys high and a
scaffold was required to reach every floor.
Until all trades had completed work on the curtain wall, the scaffolding
could not be removed. Until the
scaffolding was removed, however, the defenders were unable to do the second
and final fix work at low level in the entrance area; that would apply to
joinery and decoration at that area. In
addition, a quarry stone doorframe and revolving door had to be installed after
the scaffolding had been removed.
Consequently the atrium gantries and encasement had a critical effect on
the ability to complete the entrance area of the hotel. Support for Mr Cornish's
evidence on this matter is found in his project manager's report to the site
meeting held on
 The pursuers submitted that the work on the central atrium beam encasement was not critical; in particular, the Clerk of Works' diary disclosed that work was carried out at ground level on items such as the slab for the revolving doors, where work had largely been carried out before the scaffolding for the higher-level work was erected. In addition, the Clerk of Works' diary disclosed that a floor screed was laid in the atrium on 2 January, although it was removed on 6 and 7 January because it was not thought sufficiently durable. On 14 January work began on a slate floor, with protection being supplied as necessary. Consequently any delay in the floor related to deficiencies in the concrete screed rather than the scaffolding. Furthermore, the beam encasement was programmed on the defenders' 57-week programme (number 7/45 of process) to finish on 1 February. On that basis, evidence of Mr Cornish that proceeded on the basis of the original completion date of 25 January was, it was submitted, irrelevant. Mr Lowe expressed the opinion that the instruction relating to the atrium gantries was issued in good time having regard to the contractor's actual progress on site (report, No 6/351, page 16). In my opinion the criticism of the defenders' case on this matter is not conclusive. The fact that work on the floor was able to proceed while the scaffolding was up is hardly surprising, since the scaffolding would have been close to the wall. It was the ability to finish the floor and to finish work on the doors that was critical. Moreover, I consider that it was necessary to use the original completion date as a reference point in determining whether there was delay; the fact that other delays existed (delays which were reflected in the 57-week programme) is taken into account to the treatment of concurrent causes.
5. Fibre optic lighting in bar and breakfast bar areas
 In the bar and breakfast bar areas of the hotel fibre optic
lighting was to be provided. Mr Whitaker
dealt with this matter in his second report (No 7/8 of process) at paragraphs
2.95-2.99, and in the accompanying table on page 36. He indicated that on Thursday 21 January
1999, two working days before the then Completion Date, Keppie
sent the defenders a quotation from Carmichael Lighting Associates for the
supply of the fibre optic lighting (produced with No 7/160 of process). In their covering letter Keppie
informed the defenders that that quotation had been sent directly to the
relevant subcontractor, Browns Electrical, on
evidence of Mr Cornish was that the defenders would have required to
supply Nash Fisher with details of the fibre optic lighting two weeks before
the bar and breakfast bar carcasses were due to be delivered to site; in
addition, allowance would have to be made for the period necessary for
procurement, but Mr Cornish did not know what that was (day 4, 12.15). In
the minute of site meeting No 13 (No 7/45 of process, at page 10) it was
indicated that the procurement period was 3-4 weeks. Mr Whitaker thought that the two-week
period for the work and snagging was reasonable and that the procurement period
had to be taken into account (day 12, 1.56).
On that basis, a period of five to six weeks was required. Taken back from the Completion Date, that
indicates an Architect's Instruction at the beginning of December 1998. In my opinion that would have been a
reasonable time for the relevant Instruction.
That was, of course, very close to the point where Keppie
were instructed in place of RMJM, and that may explain why no Instruction was
issued at that time. An application in
writing had in my opinion been made, in the form of the Information Required
the foregoing basis, I consider that the failure to issue the relevant Architect's
Instruction in time to allow the installation of the fibre optic lighting prior
to the completion date would constitute a Relevant Event for the purposes of
clause 25.4.6. The revised Instruction
was in fact issued on
bar and breakfast bar had not been fitted at the time of the site meeting held
on 3 February 1999; at that time Mr Cornish reported that fitting would
not take place until 1 March (No 7/45 of process, page 10). Neither expert witness was clear as to when
the bar and breakfast bar were in fact fitted.
The last item of work relating to the fibre optic lighting was
 In this case the pursuers repeated the general criticisms that applied to all of the final fix items. Mr Lowe expressed the opinion that the instruction was issued in good time having regard to actual progress. In my opinion the general criticisms are not well founded in this case, and I prefer the evidence of Mr Whitaker to that of Mr Lowe regarding the timing of the instruction.
6. External mounted floodlights
were to be mounted on the outside of the building at plant (sixth floor)
level. The work involved is dealt with
by Mr Whitaker in his second report (No 7/8 of process, paragraphs
2.104-2.111, and table on page 39). At
site meeting No 12, held on
 Mr Whitaker's
evidence was that a reasonable time for issuing an instruction relating to the
high-level lighting was 9 December 1998; he thought that the problem should
have been identified by the design team before it was noticed by the Clerk of
Works (second report, page 39; day 12, 2.18).
Mr Cornish thought that the instruction should have been issued
even earlier (day 5, 10.45). The
relevant Instruction was in fact issued on
 The pursuers criticized the evidence of Mr Cornish and Mr Whitaker in that they both suggested that instructions should have been issued by the architect before the problem was noticed by the Clerk of Works. Mr Whitaker's evidence, at least, was that the problem should have been identified by the design team before it was noticed by the Clerk of Works. Nevertheless, a Relevant Event under clause 25.4.6 cannot occur until a written application for an instruction is made and that did not occur until 6 January. For this reason I reject the view of Mr Whitaker and Mr Cornish that the instruction should have been issued on 9 December or earlier; instead I consider 11 January to be the appropriate date. Mr Lowe gave evidence that the instruction in relation the external floodlights was issued in good time having regard to the contractor's actual progress on site. For the reasons discussed in the last paragraph I do not agree with that view. style='mso-spacerun:yes'> Counsel for the defenders drew attention to one further aspect of Mr Lowe's evidence in relation to the floodlights, and also the cooling system for the refuse room. In cross-examination (day 26, 2.42) Mr Lowe stated that the fixing of the floodlights did not affect practical completion because the floodlights were excluded from the handover. The same would apply to the stair balustrading (a matter discussed below where the defenders were in default). In re-examination (day 27, 2.19) Mr Lowe was asked whether practical completion could be achieved before the stair finishes and balustrades were completed on 12 April. He replied that these were in his opinion necessary for completion. On that basis 12 April would be the correct date for practical completion. Shortly afterwards (day 27, 2.26), Mr Lowe was asked about the position on 28 March, and in particular whether as at that date the completion of the Works had been delayed by the stair finishes and balustrades. Mr Lowe replied "Simplistically, yes". He was then asked whether the same was true of the louvres to the refuse room, and he replied "Yes. My answer applies to the other items". That indicates that Mr Lowe accepted that the major items of work that had not been completed by 29 March were causing delay as at that date. He accepted that this would apply to both the cooling system to the refuse room and the stair balustrades and finishes, but it would seem that the same point must apply to the floodlights.
7. Cooling system for the refuse room
 It was decided by the pursuers prior to site meeting No 10,
the next site meeting, held on 3 February 1999, Mr Cornish recorded in his
project manager's summary (No 7/45, page 11, item 10) that the defenders had
been instructed on 29 January to procure fans, louvres
and an air conditioning unit, and to build an enclosure in the refuse room and
carry out extensive builders work. Mr Cornish
indicated in his report that there was little prospect that that work would be
completed until mid or late March. The terms
of the instruction of 29 January are found in No 6/129 of process as AI
131. At the site meeting of 3 February
(minutes, paragraph 4.1.14) receipt of information for the condensers and
ventilation to the refuse room was confirmed.
It was noted that the subcontractor required electrical specification
for the controls. It was further
specified that the vent grille was to be full height to accommodate three
openings, and was to be coloured to match the render. It was further noted (minutes, paragraph
5.2.5) that, according to the mechanical engineer, the fan coil arrangement to
the refuse room was causing delay. The
problem of heat in the refuse room required the enclosure of the condenser unit
within partitioning inside the refuse room.
It also required that extract and ventilation fans and grilles should be
installed, along with a fan coil unit designed to contain chilled water within
the refuse room itself, in order to keep the refuse room cool. The relevant instruction for this solution is
found at AI 135, issued on
 Mr Cornish
gave evidence that the instruction relating to the chilling system in the
refuse room should have been issued as part of the first fix mechanical works,
by October 1998 (day 4, 2.42). Mr Whitaker
considered that instruction should have been issued no later than the middle of
November 1998; the matter had first been raised at the site meeting held on 4
November, and RMJM had stated that an instruction would follow (No 7/42 of
process, page 4). In their original
Information Required Schedule dated 26 January 1998 (No 7/114 of process) the
defenders had asked that information relating to electrical works should be issued
 Against the foregoing background, I am of opinion that the Architect's
Instruction issued on
to the length of time that should be allowed by way of extension, Mr Whitaker's
opinion (second report, paragraph 2.117) was that the defenders were delayed in
completing the Works until 9 April 1999 as a result of the lateness of the
instruction to provide cooling to the refuse store. Counsel for the defenders submitted that,
since the refuse store cooling was only completed on
 The pursuers submitted that Mr Cornish had not been able to indicate the effect that the works on the cooling system for the refuse room would have on overall progress of the works; moreover, he had given evidence that the content of these works was a fairly minor part of the works as a whole and did not affect work in the bedrooms. In my opinion the answer to this point is that these works occurred at the very end of the contract, and work was in fact continuing on 29 March when the handover meeting occurred. At that stage any work that is still outstanding, if it is essential for the usable occupation of the building, must necessarily be critical. That point was in effect accepted by Mr Lowe in the passages in his evidence discussed at paragraph  above; these apply equally to the cooling system for the refuse room. Moreover, in questioning by the court during evidence in chief, Mr Lowe accepted that the last item to be completed is, by definition, on the critical path (day 22, 3.14). That point can in my opinion be generalized; any work of significance that is still outstanding at handover must be on the critical path.
13 November 1998 English Landscapes, the defenders' landscape subcontractors
sent a fax to RMJM (No 7/159 of process) to state that trees of the variety
that had been specified (Liriodendron tulipifera 'Aureomarginatum') were
not available; English Landscapes suggested an alternative, namely the standard
variety of that species, and requested further instructions. RMJM's appointment
was terminated shortly thereafter. At site meeting No 12, held on
 Mr Whitaker
(second report, paragraphs 2.118-2.121 and accompanying table) expressed the
opinion that the defenders were delayed in completing the Works until 31 March
1999 as a consequence of the lateness of the instruction with regard to the
alternative variety of tree to be planted.
His view was that the instruction should have been issued no later than
 The pursuers submitted that much of the delay in planting the trees was the result of either weather conditions or default by the contractor or subcontractor. The Clerk of Works' diary (No 6/19 of process) indicated that on 8 March that it was too wet for planting and also, on 15 March, that the topsoil had not been cultivated to specification and was of poor quality. In fact the entry on 8 March notes that the soil was still too wet for planting but that the landscaping contractor was fixing trees that had already been planted. That suggests that work was progressing. I have been unable to find any entry relating to the landscaping work on 15 March. On 18 March it is narrated that the Clerk of Works went right through the landscaping scheme with the landscape architect. He agreed to write to the contractor regarding planting and the replacement of plants. The Clerk of Works then went through the scheme with the landscape subcontractor and agreed snags to be corrected. These entries do not suggest that bad weather was a serious problem; indeed, it appears from the Clerk of Works' diary that on the whole the weather during the first three weeks of March was fine, good or very good. The fact that snagging work had to be carried out is hardly surprising. In my opinion the pursuers' submission on this matter is without substance.
9. External render
 The exterior walls of the hotel at ground floor level were
to be covered with render. In the defenders' Information Required Schedule produced
for site meeting No 12 (No 7/44 of process, page 14) it is indicated that on 18
November 1998 the defenders had made an application for information in respect
of the Andura coatings that had been specified by the
architect, that information being required by 30 November. At the site meeting, which was held on
 Mr Whitaker
was of opinion that the Architect's Instruction for the render should have been
 In my opinion that Relevant Event caused completion of the
Works to be delayed beyond the Completion Date.
Mr Cornish gave evidence that work on the rendering could not begin
until the issues set out in the defenders' letter of 10 February were dealt
with (day 4, 3.27). Moreover, the
specification provided that the defenders should not start rendering work until
the colour and texture of the render had been approved. Definitive instructions were not given until
15 February, which was three weeks after the Completion Date. It is obvious that the rendering had to be
completed before the hotel could be said to be completed; indeed, the necessary
scaffolding and other equipment would make it difficult to run the hotel while
rendering work was proceeding. In his
second report Mr Whitaker expressed the opinion (paragraph 2.128) that the
defenders were delayed until
 The pursuers submitted that the completion of the external
render resulted from a series of contractor defaults relating to the eaves
cladding and the interface between the windows and the blockwork. In this respect they relied on the evidence
of Mr Lowe, who stated that the scaffolding on the outside of the building
was not taken down in line with the programme because of difficulties
encountered in the detailing of the eaves at roof level (report, No 6/351 of
process, paragraph 2.128). Mr Lowe
further stated that the scaffolding remained in place as a result of contractor
default because the installation of the cladding to the underside of the roof
overhang was not as detailed on the architect's sketch. Mr Cornish, however, gave evidence (day
7, 2.19) that the problem with the eaves arose because Kelsey, the subcontractor,
had suggested that a colour strip should be used to cover the fixings on the
eaves panelling; this was not accepted by the architect on visual grounds. It was then pointed out that the fixings
could not be seen from the ground, and the architect then accepted the
suggestion. This was the only evidence
as to what actually occurred on site, and I cannot hold that it involved contractor
default. The relevant architect's sketch
was not produced, and there was no evidence of any material departure from the
sketch. In addition, the dismantling of
the scaffolding was completed on
Delay by defenders: lifts
 The pursuers contended that, even if the defenders were correct in asserting that Completion had been delayed by the various matters discussed above, it was also delayed by two further matters, the lifts and the stair balustrades. Both of these were the responsibility of the defenders or the defenders' subcontractors. They accordingly operated as concurrent causes of the delay. The delay caused by these two items was such that completion could not have occurred any earlier than it did. This contention raises the issue of concurrent causes, discussed at paragraphs - above. Before considering that issue, however, I must deal with the evidence relating to the lifts and the stair balustrades.
relation to the lifts, in the defenders' programme work was originally planned
to start on
 Mr Whitaker
ultimately conceded (day 15, 11.18) that the lifts had been installed late, and
that this was a problem for which the defenders had been responsible. He further accepted that it involved a delay
that was concurrent with other delays until
 In my opinion the pursuers were correct in asserting that Completion was delayed by work on the lifts. That delay was the responsibility of the defenders and their subcontractors; indeed, the defenders do not argue the contrary. I accordingly conclude that the delay in completing the lift installation was a concurrent source of the delay in Completion. That delay lasted until 24 March, when it is agreed that the lift installation was completed.
Delay by defenders: stair balustrades
the Bills of Quantities stair balustrading and
finishes are listed as provisional sums.
It is noted that the works are to be executed by a domestic subcontractor. In the defenders' original construction
programme (No 7/156 of process) stair balustrading
appears in the "finishes" section.
The dates for starting and finishing this activity were
"[Mr Cornish] advised all concrete in atrium and lift lobby will be skim plastered to remedy inaccuracies in concrete. [Mr Cornish] confirmed angle edge beads will be used to ensure straight, clean edges of concrete".
That work was necessary in order to
carry out the work on the stair balustrades and finishes. The relevant architect's
instructions (Nos 78 and 105) were issued on 4
 Problems occurred as the stair balustrading work continued. The Clerk of Works noted concerns about quality on 2 March 1999 and recorded that the need to carry out drilling for base plates created dust, which had an impact on the snagging of the atrium area (9, 11 and 12 March 1999; Mr Cornish, day 7, 12.37). Although it is agreed that completion occurred on 29 April, some snagging work occurred as late as 20 April (Clerk of Works' diary). It was not possible to achieve Practical Completion without the main stair and the fire escape stairs; for these to the available for use the balustrading had to be complete, as the handrail was obviously necessary (Mr Cornish, day 7, 12.47). The defenders did not seek any extension of time in respect of the stair balustrades.
 In my opinion completion was delayed by the work on the
stair balustrades. That delay was the
responsibility of the defenders as contractor; that was not in dispute. I accordingly conclude that the work on the
stair balustrades and the stair finishes was a concurrent source of the delay
in completion. That delay lasted until
 I should mention one further matter. In their written submissions the pursuers referred to certain other items of work that were said to have delayed Practical Completion and which were the responsibility of the defenders or their subcontractors. These included the installation of utilities and lagging in the plant room. Both of these, however, were considered by Mr Lowe not to be on the critical path. It follows that the only delay that they can have caused to Practical Completion is the delay in their own completion. It is not entirely clear when work on utilities came to an end; the gas supply to the hotel was turned on on 15 February, and the gas main itself appears to have been installed either on or shortly after 5 February (Mr Cornish, day 7, 3.08). In all the circumstances I do not regard this activity as of great significance. It was not explored at great length in evidence, and it is not clear on the evidence what the causes of the delay were; it is impossible to exclude the possibility that progress was slow simply because it was known that completion was going to be delayed for other reasons. Lagging in the plant room appears to have continued, according to the Clerk of Works' diary, for most of February and until 10 March. On 15 March it is recorded that the defenders were cleaning up in the plant room. The issue of the plant room lagging was first raised by the pursuers in cross-examination of Mr Whitaker. Counsel for the defenders objected to the line of evidence, on the basis that it had not been put to Mr Cornish during his cross-examination. That objection was maintained in submissions. In my opinion the objection was well founded, and I sustain it. Mr Cornish was the obvious witness of fact on this matter, and elementary fairness dictates that it should have been put to him. He might have been able to provide some reason for the apparent delay. For this reason I will disregard the issue of the plant room lagging.
 The next issue that must be considered is the application of clause 13.8 of the Conditions of Contract. Clause 13.8 sets out certain procedures that are to be followed if the contractor considers that any architect's instruction or the equivalent will require either an adjustment to the contract sum or delay the completion date. So far as material it is in the following terms:
"13.8.1 Where, in the opinion of the Contractor, any instruction, or other item which, in the opinion of the Contractor, constitutes an instruction issued by the Architect, will require an adjustment to the Contract Sum and/or delay the Completion Date, the Contractor shall not execute such instruction (subject to Clause 13.8.4) unless he shall have first submitted to the Architect, in writing, within 10 working days (or within such other period as may be agreed between the Contractor and the Architect[)] of receipt of the instruction, details of:
1. Initial estimate of the adjustment (together with all necessary supporting calculations by reference to the Contract Documents);
2. Initial estimate of the additional resources (if any) required and his method statement for compliance;
3. Initial estimate of the length of any extension of time to which he considers he is entitled under Clause 25 and the new Completion Date (together with all necessary supporting documentation by reference to the Master Programme);
4. Initial estimate of the amount of any direct loss and/or expense to which he may be entitled under Clause 26; and
5. Any such other information as the Architect may reasonably require.
13.8.2 The Contractor and the Architect shall then, within 5 working days of receipt by the Architect of the Contractor's estimates, agree the Contractor's assessments. Following such agreement, the Contractor shall immediately thereafter comply with the instruction and the Architect shall grant an extension of time under Clause 25.3 of the agreed length (if any) and the agreed adjustments (if any) and the agreed adjustments (if any) in relation to clauses 126.96.36.199 and 188.8.131.52 shall be made to the Contract Sum.
13.8.3 If agreement cannot be reached within 5 working days of receipt by the Architect of the Contractor's estimate on all or any of the matters set out therein; then;
1. the Architect may nevertheless instruct the Contractor to comply with the instruction; in which case the provisions of Clauses 13.5, 25 and 26 shall apply; or
2. the Architect may instruct the Contractor not to comply with the instruction, in which case the contractor shall be reimbursed all reasonable costs associated with the abortive [instruction].
13.8.4 The Architect may, by notice to the Contractor before or after the issue of any instruction, dispense with the Contractor's obligation under Clause 13.8.1, in which case the Contractor shall immediately comply with the instruction and the provisions of Clauses 13.5, 25 and 26 shall apply.
13.8.5 If the Contractor fails to comply with any one or more of the provisions of Clause 13.8.1, where the Architect has not dispensed with such compliance under Clause 13.8.4, the Contractor shall not be entitled to any extension of time under Clause 25.3".
 The terms of clause 13.8 were considered by Lord Macfadyen when the action was at debate; his decision is reported at 2002 SLT 781. Lord Macfadyen made the following comments (at 793):
" In my opinion, the language of clause 13.8 is prima facie applicable to all architect's instructions, including those in respect of the expenditure of provisional sums. There is no qualification of the reference in clause 13.8.1 to architect's instructions to suggest that any subcategory of such instructions is to be excluded from the scope of the clause. The repetition of the substance of clause 13.3.1 in clause 13.8.6, although apparently redundant, lends support to the contention that clause 13.8 applies, without distinction, to all architect's instructions.
 In my view a distinction falls to be drawn between, on the one hand, a late instruction which, simply because of its lateness, gives rise to a need to adjust the contract sum and/or grant an extension of time and, on the other hand, an instruction which, although late, is of such a nature that it would, whenever issued, have given rise to a need to make such an adjustment or grant such an extension. The latter category of instruction falls, in my view, within the scope of clause 13.8, whereas the former does not. It is in my view difficult to formulate the distinction more precisely in the abstract. It would, in my view, be wrong to say simply that clause 13.8 has no application to late instructions. On the other hand, a failure to comply with clause 13.8 will not, in my view, exclude a claim for extension of time in so far as the extension is made necessary by the lateness of the instruction as distinct from its content.
 In my opinion the architect's power under clause 25.3.3 [to grant extensions of time] must be read subject to the special provision of clause 13.8.5. Clause 13.8.5 defines the effect of failure to comply with the provisions of clause 13.8.1 as being that 'the Contractor shall not be entitled to any extension of time under clause 25.3'.... The contractor's right to [an extension] is, therefore, in my opinion, removed, in terms of clause 13.8.5, if the contractor fails to comply with the provisions of clause 13.8.1".
When the defenders reclaimed against Lord Macfadyen's decision his opinion on the foregoing matters was not challenged.
 Nevertheless, in his submissions senior counsel for the pursuers contended that Lord Macfadyen's construction of clause 13.8 was mistaken. He emphasized the wording of clause 13.8.1, which refers to "any" instruction which in the opinion of the contractor would require an adjustment to the Contract Sum or delay the Completion Date. No distinction is made between content and timing; instead all that is relevant is the impact of an Architect's Instruction on cost or completion. The wording of the remainder of the clause was likewise mandatory; clause 13.8.5 denied the contractor a right to "any extension of time under clause 25.3".
 In my opinion Lord Macfadyen's construction of clause 13.8 is clearly correct. That construction is based on a distinction between delay caused by the lateness of an instruction and delay caused by its content; the clause applies to the latter type of delay but not to the former. That makes practical sense. This can be seen by considering a hypothetical example where the delay is clearly caused by lateness alone. Suppose that external walls are to be covered in render of a particular specification, the colour to be advised by the architect. According to the contractor's programme work on the render is to start on 15 October and, because of a 14-day lead-in time, information on the colour is required by 1 October. The architect instructs the colour on 10 October. Because of the lead-in time, work cannot begin until 25 October. In those circumstances, what would be the point of using the clause 13.8 procedure when the architect's instruction was received on 10 October? There is no additional cost. So far as lateness is concerned, delay is inevitable because the instruction was 10 days late. Using the clause 13.8 procedure does not give the architect the option of cancelling it, or instructing something else; that would merely add to the delay. The sensible course is clearly that the contractor should proceed with the work immediately. In my opinion the clause cannot have been intended to operate in such circumstances. The same must be true in all cases where delay is caused by the mere lateness of an instruction or variation, rather than its content. In conclusion, I would merely add that clause 13.8 does not appear to have been well thought through. It is, so far as I am aware, an unusual clause, innovating upon the standard JCT scheme. In these circumstances I do not see any need to give it a liberal construction; it should be construed so that it does not operate where it makes no contractual sense. Moreover, support for Lord Macfadyen's construction can be found in the wording of clause 13.8.1 itself. Where the content of an instruction is the problem, it can be said that it is the "instruction" (the word used in clause 13.8.1) that has caused the delay. Where delay in the lateness of the instruction is the source of the problem, however, it is the lateness rather than the instruction that causes the delay. Exactly the same analysis applies to variations. style='mso-spacerun:yes'> A variation may or may not cause delay because of its content. If the work instructed is fundamentally different, it is quite possible that the content will give rise to delay. Where the variation is relatively minor, however, it is unlikely that content will cause delay; nevertheless, if the variation is issued late that may cause delay, and the example given above is still in point. In every case it is necessary to examine the particular instruction or variation to discover whether any resulting delay is caused by lateness or content.
 On this basis, I am of opinion that with one exception all of the Architect's Instructions founded on by the defenders for the purposes of the counterclaim are outwith the scope of clause 13.8. In every case except the gas venting, for the reasons discussed above in relation to the individual Architect's Instructions, I consider that it was the lateness rather than the content of the Instruction that caused the delay to completion. The result is that in none of these cases does clause 13.8 preclude the defenders from claiming an extension of time under clause 25. In relation to the gas venting scheme, the defenders admitted that it was content rather than lateness that caused the delay. In this case the defenders did not make use of the clause 13.8 procedure. In these circumstances it is necessary to consider the issues of waiver and personal bar.
Waiver and personal bar
 Waiver involves the abandonment of a right: Armia Ltd v Daejan Developments Ltd, 1979 SC(HL) 56, at 69 per Lord Fraser of Tullybelton; and at 72 per Lord Keith of Kinkel. The word "right" must in my opinion be relatively widely construed. It should include not only a right in the narrowest sense, consisting of a claim against another person, but should also extend to other forms of legal entitlement. These include entitlements that may more properly be described as a privilege or an immunity; a privilege is an entitlement to prevent another person from exercising a claim-right, and an immunity is an entitlement to prevent another person from exercising a power. (The terminology used here is derived from W.N. Hohfeld, Fundamental Legal Conceptions as applied in Judicial Reasoning, (New Haven, 1923)). I am of opinion that the pursuers' right to invoke clause 13.8 is properly characterized as an immunity; the defenders have a power to use that clause to claim an extension of time, and the pursuers have an immunity against that power if the defenders do not fulfil the requirements of the clause. In my opinion an immunity can be the subject of waiver. That view is I think supported by the decision of Lord Eassie in E & J Glasgow Ltd v UGC Estates Ltd,  CSOH 63, where (at paragraph ) he states:
"In a contractual context, waiver of a contractual term may necessarily imply that something which does not satisfy all the contractual conditions is yet to be treated as being within those provisions because the party having an interest to insist on full satisfaction has either expressly, or by implication arising from the factual circumstances, waived his right to insist on one or more of the contractual conditions being duly fulfilled. In ordinary usage, waiving a contractual term is indeed to say that one is not insisting on one's right to require due observance of the term....[T]he authorities illustrate that a contractual term which is definitive of a contractual entitlement may be waived".
 The defenders issued a series of notices in terms of clause
25 of the Contract Conditions (Nos 7/130-7/152 of
process). For the purposes of the
following analysis I will concentrate on the first of these (No 7/130), which
related to the gas venting scheme; nevertheless I think that exactly the same
analysis applies to the later notices.
The first delay notice was issued on
on 9 October and 17 November 1998 letters were written by the architect, RMJM,
in relation to the claim for an extension of time as a result of the gas
venting instructions (Nos 6/36 and 6/37 of
process). Nothing was said in these
letters about clause 13.8. Instead, the
defenders' claim was rejected because, it was said, the defenders had agreed to
absorb the delay; I discuss this matter at paragraph . Moreover, the letter of 9 October dealt with
claims under express reference to clause 25.
RMJM indicated that in their view the gas venting instruction
constituted, a Relevant Event under clause 184.108.40.206, and that event caused the
defenders delay. A similar point can be
made in relation to other letters from the architect; these include RMJM's letter of
 The pursuers argued that there was no evidence to suggest
that they were directly involved in any decisions relating to extension of time
taken by the architect. Consequently the
defenders required to rely on the actings of the architect
as agent of the pursuers. Nevertheless,
the architect had no implied authority to vary or waive the terms of a building
contract. Reference was made to
 Clause 13.8 must in my opinion be construed as imposing procedural requirements, rather than dealing with matters of substance. In respect of any extension of time, the substative provision is clause 25; in respect of prolongation costs and other form of direct loss and expense, it is clause 26. Clause 13.8 is clearly conceived against the background of these two clauses. It applies where in the contractor's opinion any instruction will either require an adjustment to the Contract Sum or delay the Completion Date (clause 13.8.1). In that event, the contractor is directed not to execute the instruction without first submitting to the architect initial estimates of various matters, including the likely adjustment to the Contract Sum, the likely extension of time that will be required and the estimated amount of direct loss and expense under clause 26. Thereafter the contractor and the architect may, within five working days, agree the contractor's estimates; if they fail to do so the architect is given the choice of ordering compliance with the instruction, in which case the provisions of clauses 25 and 26 apply, or instruct the contractor not to comply with the instruction. Essentially, the however, the clause is designed to provide a pre-estimate of the cost in time and money of complying with a proposed instruction. In that way the cost can be agreed conclusively in advance; failing that the architect may decide to withdraw the instruction, usually, it may be supposed, because the cost is too great; or alternatively the architect can proceed with the instruction regardless, in which case clauses 25 and 26 apply. It follows in my opinion that the function of the clause is essentially procedural in nature. There is a facility to agree certain matters, but failing that the substantive provisions of the contract apply.
further aspect of clause 13.8 must be considered; this is the effect of clause
13.8.4 and clause 13.8.5. Clause 13.8.4
authorizes the architect, by notice the contractor, to dispense with "the contractor's
obligation" under clause 13.8.1, in which case clauses 25 and 26
apply. Clause 13.8.5 provides that, if
the contractor fails to comply with clause 13.8.1, he will not be entitled to
any extension of time under clause 25.
There is thus an express power to dispense with the requirements of
clause 13.8.1, and the question arises as to whether this impliedly excludes
waiver of the clause. In some cases an
express power to dispense with a provision might well exclude a right of
waiver. Nevertheless, I think that such
cases are exceptional, and that the norm is that waiver should be available
even when there is an express right of dispensation. My reason for this conclusion is
twofold. First, waiver, like other forms
of personal bar, is based on elementary considerations of justice; these are
well expressed by Dixon J. in a passage cited in paragraph  below in
relation to the right of estoppel in the law of
 In relation to the gas venting scheme, I am of opinion that the pursuers waived the requirements of clause 13.8, both through their own actings at the meeting held on 8 April and through the actings of RMJM in their approach to the claim intimated on 31 March. The function of clause 13.8 is to ensure that, if an instruction or variation is issued, the question of delay and any financial consequences are dealt with immediately. In that way the architect is able to assess the consequences of the relevant instruction and to decide whether to maintain the instruction or to revert to the previous position. If an application is made for an extension of time, however, that flatly contradicts the scheme of the clause. That is in my opinion sufficient to put the architect on notice that clause 13.8 is not being used. The same applies to the employer if he becomes aware of the claim for an extension of time. Failure to invoke clause 13.8 is of significance, given its contractual importance, especially in working through the legal and financial consequences of the step that the architect proposes to take. If the claim is made for an extension of time, there is in my view a very obvious need to invoke clause 13.8, if the immunity conferred by that clause is truly to be invoked. In the present case no attempt was made to invoke clause 13.8, or indeed to refer to it in any way. In these circumstances, in particular having regard to the facts set out at paragraphs  and  above, I am of opinion that the immunity contained in that clause was waived. In drawing this inference I rely principally upon the immediate reaction to the defenders' claim, as disclosed at the meeting held on 8 April. It is clear from the minutes of that meeting that the claim for an extension of time was discussed at length. In view of the apparent importance of clause 13.8, it would be very surprising if no mention were made of the clause unless either the pursuers or the architect, acting on their behalf, had decided not to invoke the clause. It is adding significance of both representatives of the pursuers and representatives of RMJM were present at the meeting, yet neither mentioned the clause.
 One further requirement of waiver is that the person asserting it must have conducted his affairs in reliance on the waiver, although there is no need for him to have acted on it to his prejudice: Armia Ltd v Daejan Developments Ltd, supra, per Lord Fraser of Tullybelton at 69 and per Lord Keith of Kinkel at 72. In the present case I am of opinion that the defenders did clearly act on the basis of the waiver at the meeting held on 8 April, in that they pursued a claim under clause 25 without any reference to clause 13.8. No doubt, if clause 13.8 had been applied strictly, the defenders would have been out of time prior to 8 April, but that did not happen. The defenders continued to pursue claims under clause 25 in relation to both the gas venting scheme and the various other sources of delay discussed previously, and that is in my opinion sufficient to satisfy the requirement of conducting affairs in reliance on the waiver.
the pursuers it was submitted that the defenders had led no evidence to suggest
that the architect was even aware of the terms of clause 13.8 when he issued
decisions in relation to applications for extension of time. Waiver of a right cannot be inferred from
circumstances that may be consistent with its retention; moreover, because
waiver involves the abandonment of a right for all time it cannot be based on a
mere oversight. Reference was made to Evans v Argus Healthcare (Glenesk) Ltd, 2001
SCLR 117, at paragraph ; to Armia Ltd v Daejan Developments Ltd, supra, at 69 and 71-72; and to
Oak Mall Greenock Ltd v McDonald's
"Where A has by his words or conduct justified B in believing that a certain state of affairs exists, and B has acted upon such belief to his prejudice, A is not permitted to affirm against B that a different state of fact existed at the same time".
The rationale of the doctrine of personal bar is set out by LP Rodger in William Grant & Sons Ltd v Glen Catrine Ltd, 2001 SC 901; citing Dixon J. in Grundt v Great Boulder Pty Gold Mines Ltd, (39) 59 CLR 641, at 674-675, Lord Rodger said (at 921):
"[T]he basal purpose of the doctrine of estoppel 'is to avoid or prevent a detriment to the party asserting the estoppel by compelling the opposite party to adhere to the assumption upon which the former acted or abstained from acting. This means that the real detriment or harm from which the law seeks to give protection is that which would flow from the change of position if the assumption were deserted that led to it. So long as the assumption is adhered to, the party who altered his situation upon the face of it cannot complain. His complaint is that when afterwards the other party makes a different state of affairs the basis of an assertion of right against him then, if it is allowed, his own original change of position will operate as a detriment. His action or inaction must be such that, if the assumption upon which he proceeded were shown to be wrong and an inconsistent state of affairs were accepted as the foundation of the rights and duties of himself and the opposite party, the consequence would be to make his original act or failure to act a source of prejudice'".
 It is accordingly necessary for the defenders to establish both a representation, express or implied, that a certain state of affairs exists and actings on the faith of that representation, to the prejudice of the person who so acts. In relation to the gas venting instruction, I think that an implied representation can be inferred from the actings of both the pursuers and RMJM at the meeting held on 8 April. In this case, however, I am of opinion that it cannot be said that the defenders acted on such a representation to their prejudice. What they did was to pursue a claim under clause 25, without regard to the implications of clause 13.8. If clause 13.8 had been invoked, however, the defenders would have had no claim under clause 25 because any such claim was barred by clause 13.8.5. Thus they were not actually prejudiced. No doubt they incurred expense in pursuing the clause 25 claim, but I do not think that that is sufficient to amount to prejudice for the purposes of the law of personal bar.
 Because of the view that I have taken on the construction of clause 13.8, it is not necessary to consider how waiver or personal bar would apply to elements of the defenders' claim other than the gas venting instruction. In these cases, however, a broadly similar analysis would apply, subject to one exception. In relation to personal bar, as against waiver, I think that it could be said that there was prejudice, in that the defenders repeatedly failed to make use of the clause 13.8 procedures on the assumption that their claims were being dealt with under clause 25 alone.
 I accordingly conclude that the delay in completion was the result of concurrent causes. The majority of those were the result of the late instructions or variations issued by the architect, and are Relevant Events for the purposes of clause 25; two of those causes, however, the work on the lifts and the work on the stair balustrading, were the fault of the defenders or their subcontractors. In my opinion none of the causes of delay can be regarded as a "dominant" cause; each of them had a significant effect on the failure to complete timeously. The pursuers advanced an argument based on the proposition that the items involving contractor default, the lifts and the stair balustrades, were the "dominant" cause of the delay, but I am of opinion that this contention must be rejected. Indeed, the lateness of the instructions relating to the gas venting scheme and the roof steelwork had a major effect on the progress of the works, to a substantially greater degree than the items involving contractor default. Consequently the case is one of true concurrent causes. In those circumstances the correct approach is in my opinion that set out at paragraph  above. Clause 25 requires that the architect should exercise his judgment to determine the extent to which completion has been delayed beyond the Completion Date by Relevant Events, or non-contractor's risk events. Put another way, that involves a determination of the aggregate period within which the Works as ultimately defined should have been completed having regard to the incidence of Relevant Events. That determination must be made on a fair and reasonable basis, as required by clause 25. In a case such as the present where there is true concurrency between Relevant Events and events that involve contractor default, apportionment will frequently be appropriate. In my opinion this is such a case. Apportionment enables the architect to reach a fair assessment of the extent to which completion has been delayed by Relevant Events while at the same time taking into account the effect of other events which involve contractor default. Where the decision of the architect is challenged, the court must of course perform the same exercise.
 That leads on to the question of how the exercise of apportionment is carried out. That exercise is broadly similar to the apportionment of liability on account of contributory negligence or contribution among joint wrongdoers. In my opinion two main elements are important: the degree of culpability involved in each of the causes of the delay and the significance of each of the factors in causing the delay. In practice culpability is likely to be the less important of these two factors. Nevertheless, I think that in appropriate cases it is important to recognize that the seriousness of the architect's failure to issue instructions or of the contractor's default may be a relevant consideration. The causative significance of each of the factors is likely to be more important. In this respect, two matters appear to me to be potentially important. The first of these is the length of the delay caused by each of the causative events; that will usually be a relatively straightforward factor. The second is the significance of each of the causative events for the Works as a whole. Thus an event that only affects a small part of the building may be of lesser importance than an event whose effects run throughout the building or which has a significant effect on other operations. Ultimately, however, the question is one of judgment.
1. Gas venting: 18 February (but concurrent with roof steelwork).
2. Roof steelwork: 1 March.
3. En suite fittings: 25 March.
4. Bedhead lighting: 19 February (or 17 February according to Mr Whitaker).
5. Trouser presses: 13 March.
6. Central atrium beam encasement: 1 March.
7. Fibre optic lighting: 15 March.
8. External mounted floodlights: 31 March.
9. Cooling to refuse room: 12 April.
10. Trees: 19 March.
11. External render: 8 March.
The pursuers have established two concurrent causes: the installation of the lifts, which delayed completion until 24 March, and the construction of the stair balustrades, which delayed completion until 12 April.
 The original Completion Date was
 In considering the extent to which that period should be
reduced, the matters referred to at paragraph  must be considered. I do not consider culpability to the a major
factor; nevertheless, the sheer quantity of late instructions following Keppie's appointment is I think significant; so is the fact
that the failure to issue instructions occurred following requests for
information which started (during the course of the Works) on 7 October
1998. So far as the causative significance
of each of the events is concerned, all caused some delay, although the delay
resulting from the gas venting instruction was concurrent with 3 1/2 weeks of
the delay resulting from the late instruction relative to the roof
steelwork. The two items that had the
longest lasting effect were the cooling to the refuse room and the stair
balustrades, both of which concluded on about 12 April. In relation to the causative significance of
each of the events for the Works as a whole, I must I think take account of the
fact that items such as the en suite fittings, the bedhead
lights and the trouser presses affected all of the bedrooms in the hotel. Finally, I must take account of the fact that
the number of Relevant Events is substantially greater than the number of items
for which the defenders are responsible; moreover some of them, notably the gas
venting and roof steelwork instructions, related to important matters that had
significant effects on the overall progress of the Works. Taking all these circumstances into account,
I am of opinion that the part of the total delay apportioned to Relevant Events
should be substantially greater than that apportioned to the two items for
which the defenders are responsible. I
consider that a fair and reasonable result would be that the defenders are
entitled to an extension of time of nine weeks from the original Completion
Date. On that basis I conclude that
completion has been delayed beyond the completion Date by Relevant Events for a
period of nine weeks, or until
 In the counterclaim the defenders' fourth conclusion (as
amended) is for payment of the sum of £27,069.10, inclusive of value added
tax. This is said to represent the costs
incurred by the defenders as a result of the prolongation of the contract works. In the joint minute it is agreed that, to the
extent that the Works were prolonged beyond the original Completion Date, the
defenders incurred loss and/or expense arising from the prolongation of the
 The defenders seek to recover their prolongation costs under clause 26 of the JCT Standard Form. Clause 26 has two formal requirements. First, the contractor must have must have made written application to the architect stating that he has incurred or is likely to incur direct loss and/or expense in the execution of the Contract because the regular progress of the Works had been was likely to be materially affected by failure to receive timeous instructions. Secondly the application must be made as soon as it had become, or should reasonably have become, apparent that the regular progress of the Works had been or was likely to be affected. In my opinion both of these requirements were satisfied in the present case. The defenders made a series of written applications to recover direct loss and expense that they alleged had been caused by prolongation; these are found in Nos 7/137, 7/141, 7/142, 7/144, 7/146, 7/147, 7/149 and 7/150 of process. It appeared that the applications were made as soon as it became apparent that the Works might be prolonged.
 The defenders' claim is based on clause 26.2.1; it is said that the defenders did not receive necessary instructions in due time. For the reasons discussed above in relation to the defenders' claim for an extension of time, I am of opinion that the defenders did not receive instructions in due time in respect of the roof steelwork and the nine items narrated above where instructions were given following the replacement of RMJM by Keppie. The reasoning applicable to an extension of time seems to me to be equally applicable to a claim for direct loss and expense based on clause 26.2.1. It was clear in my opinion that the regular progress of the Works was "materially affected" (clause 26.1) by the instructions that were not received in due time; that appeared from the evidence that is summarized above in relation to an extension of time. Mr Cornish was asked (day 4, 3.48) how satisfied he was that late instructions were critical to the defenders' completion of the Works. Mr Cornish replied that the late instructions were "completely critical". He went on to say that he was satisfied that they affected the regular progress of the Works "in a very profound way". I thought that these views were justified by the evidence as a whole. I accordingly conclude that the requirements of clause 26 are satisfied.
 For the pursuers it was submitted that the defenders' claim for propagation costs should be refused for the same reasons as were advanced in opposition to their claim for an extension of time. I have granted an extension of time, and consequently I reject this part of the argument. It was further submitted that, even if the defenders were entitled to an extension of time to resist liability for liquidated and ascertained damages, they were not automatically entitled to prolongation costs for an identical period. It was submitted in particular that, if a contractor incurs additional costs that are caused both by an employer delay and by a concurrent contractor delay, the contractor should only recover compensation to the extent that it was able to identify the additional costs caused by the employer delay as against the contractor delay. If the contractor would have incurred the additional costs in any event as a result of the contractor delay, he would not be entitled to recover those additional costs.
 It is I think correct that a claim for prolongation costs
need not automatically follow success in a claim for extension of time. The wording of clause 26 differs from that of
clause 25, and different considerations may apply. In the present case, however, I am of opinion
that the claim for prolongation costs should follow the result of the claim for
extension of time. In this respect the
decision in John Doyle Construction Ltd v
Laing Management (
 It will be apparent that I have rejected the pursuers' argument that, if prolongation costs are caused both by an employer delay and by a concurrent contractor delay, the contractor will not be entitled to recover such costs if he would have incurred them as a result of the contractor delay. That approach seems to be based on a rigidly logical application of the principles of causation as they apply in the general law of contract and delict. Under clause 26, however, as with clause 25, I am of opinion that such an approach is not appropriate; instead, the direct loss and expense sustained by the contractor should be apportioned between the events for which the employer is responsible and the events for which the contractor is responsible.
 For the reasons stated above I conclude that the pursuers
are not entitled to declarator that the Completion