Few topics generate more argument in delay claims than concurrent delay. Employers raise it to defeat or reduce EOT claims; contractors fear it because it can wipe out prolongation cost recovery even where an extension of time is granted. Yet true concurrency is rarer — and narrower — than most rejection letters suggest.
What is concurrent delay?
In its strict sense, concurrent delay occurs when two or more delay events — at least one an employer risk and one a contractor risk — cause delay to completion at the same time, and each would have delayed completion on its own. The often-cited English definition describes it as “a period of project overrun which is caused by two or more effective causes of delay which are of approximately equal causative potency.”
That definition sets a high bar. Two events merely overlapping in time is not concurrency. If the works were already in culpable delay and an employer event occurs that causes no additional delay to completion, the events are not truly concurrent — one is driving the completion date and the other is not.
True concurrency vs the “concurrent-sounding” situations
- Sequential delays: an employer delay followed by a contractor delay (or vice versa) is not concurrency — each period is assessed on its own cause.
- Pacing: a contractor that deliberately slows non-critical work to match an employer delay is not in concurrent delay — though it must be able to evidence that the slowdown was a conscious pacing decision.
- Float-absorbing events: an event that only consumes float does not delay completion at all, and cannot be concurrent with anything.
The consequences: time and money are treated differently
Time
The widely adopted approach — reflected in the SCL Delay and Disruption Protocol and in English authority such as Henry Boot v Malmaison — is that where a contractor delay runs truly concurrently with an employer delay, the contractor should still receive its extension of time for the employer delay. The employer risk event still prevents completion, and the EOT protects the contractor from liquidated damages for that period.
Money
Prolongation costs follow a different rule. To recover time-related costs the contractor must show the costs were caused by the employer delay. Where its own culpable delay ran concurrently, it would have incurred those site overheads anyway — so the usual outcome is “time but no money”: EOT granted, prolongation costs refused for the concurrent period.
Regional and contractual nuances
Under UAE law there is no binding doctrine of concurrency; tribunals often apportion responsibility guided by good faith principles in the Civil Code, and the reasoning in each case turns on the evidence. In the UK, the position also depends on the contract — some bespoke amendments expressly make concurrency a bar to EOT, and English courts have upheld such clauses. Always check the contract before assuming the Protocol position applies.
How to deal with concurrency allegations in practice
- Interrogate the alleged contractor delay: was it actually on the critical path, or merely consuming float?
- Test causative potency: would the alleged contractor event have delayed completion by itself, on the programme as it stood at the time?
- Check the timing: events must affect completion during the same period — overlap on a bar chart is not enough.
- Evidence pacing decisions contemporaneously, in progress reports or correspondence, not retrospectively in the claim narrative.
- Keep cost records separable so that prolongation costs can be tied to specific windows of employer delay.
The takeaway
Concurrency is a precise legal and technical concept, not a catch-all defence. Whether you are advancing an EOT claim or responding to one, the analysis must identify the actual critical path, the true cause of delay in each window, and the contract’s allocation of risk. That is detailed, records-driven work — and it is exactly what we do.
Facing a concurrency argument on a live claim? Contact Logic Line Consultancy for a review of your position before you respond.