Addressing the issue of concurrent delay is one of the most important factors to consider when demonstrating an extension of time claim. As a result of this it is becoming increasingly common for concurrent delay clauses to be included within construction contracts. The absence of such provision frequently gives rise to disputes.
The commonly accepted and approved definition7 of concurrent delay is when there are two or more delay events occurring at the same time which are approximately equal in terms of causing delay to the completion date. This narrow definition results in the occurrence of true concurrency being rare and frequently this principle is falsely alleged in instances where one of the events can properly be said to be only a minor cause of the delay, and so can be disregarded altogether, resulting in there being no concurrency.
There are broadly three different situations in which concurrent delay could occur. Firstly, and most simply, when both an employer delay and a contractor delay each simultaneously affect an activity on the critical path and thus delay the overall project. The second is where there is an employer and contractor delay each affecting different critical paths of activities within the programme at the same time, but where the delays to each of these paths equally affect the overall completion of the project. The third scenario is where during a period of either (contractor or employer) delay there is a further delay attributable to the other party which equally causes a delay to the completion date during the period of time over which it occurs.
Following the decision in Walter Lilly & Company Ltd v Mackay and another [2012]8 the preferred position9 states that in each of these scenarios, where a contractor's delay runs truly concurrent with an employer's delay, the contractor's delay should not reduce any extension of time due.
Critical path analysis
Whilst case law suggests that there is no requirement for an extension of time application to contain a critical path analysis10, and that instead it is possible to leave it to the employer to form an opinion as to the effect of an alleged delay with or without employing its own analysis, it would naturally be preferable for the contractor to demonstrate its claim for delay. Often a contractor's allegation that an excusable event delayed the completion date is unfounded and, upon the implementation of a proper critical path delay analysis, it becomes apparent that the critical progress of the works remained unaffected by the event being claimed by the contractor.
There are various methods of critical path analysis which exist for analysing and demonstrating the effects of delay events.
The methodology selected to objectively illustrate cause and effect within an extension of time claim is normally dictated by the timing of the analysis together with the availability of contemporaneous records and time/resource. The timing is of relevance as the use of a prospective analysis (based upon the likely effects of a delay) or a retrospective analysis (based upon actual fact) will provide different results.
The SCL delay and disruption protocol11 provides guidance as to appropriate methods of delay analysis. In doing so it is to be noted that different methods of critical path analysis have the ability to produce very different results and the selection of a suitable technique requires careful consideration with regards to achieving the goal of demonstrating and illustrating the critical effects of the delay events complained of.