Michael. P. Gerrard clarifies the issue of concurrent delays
With building projects declining, more contractors will be chasing fewer contracts resulting in reduced tender prices as competition intensifies. Although this may sound like good news for an employer, it isn’t necessarily good news for contract administrators who must be prepared for an avalanche of claims from contractors eager to improve on their low margins.
One of the most common ways for a contractor to achieve this is via extension of time claims. So in preparation for such claims, it makes sense to ensure clarity of thought on the thorny issue of concurrent delay claims.
For there to be concurrent delays, (one event is a relevant event and the other a contractor culpability) both events must be shown to be on the critical path of the programme. [The Royal Brompton Hospital NHS Trust –v– Watkins Gray International (UK)  TCC (Royal Brompton)]
An event complained of must be shown to have been on the critical path as opposed to merely concurrent with the critical path. If an event is not on the critical path, it cannot affect completion - and hence there is no entitlement to time. [Royal Brompton]
This is where delays (with only one being a relevant event) start and end simultaneously. Both must be on the critical path of the programme, which by definition, would be likely to affect the date for completion. [Henry Boot Construction (UK) Ltd –v– Malmaison Hotel (Manchester) Limited  (Henry Boot)]
ABSENCE OF CONCURRENCY
When a relevant event occurs after an event that the contractor was culpable for, this should not bar the contractor from being potentially entitled to an extension of time. [City Inn Limited –v– Shepherd Construction Limited  (City Inn)]
FAIR AND REASONABLE
Where there are two concurrency of causes, (one being a contractor culpability and the other a relevant event) and the relevant event is likely to delay the works beyond the completion date, then providing the architect considers it fair and reasonable to do so, an extension of time should be granted. [Henry Boot & City Inn]
BURDEN OF PROOF
There is no relief for the contractor from the burden of proving that the event was a relevant event and was on the critical path of the programme (as opposed to being merely an operational activity which happened to be concurrent with the critical path).
In summary, and in the context of entitlement to an extension of time:
Concurrency of an event, whether a relevant event or contractor culpability, must necessarily be shown to be on the programme’s critical path, the completion of the works of which is likely to be delayed thereby beyond the completion date.
A relevant event can occur either simultaneously or post a contractor culpable event, both of which may be considered for an extension of time providing the event is proved on balance to be on the critical path.
© Michael P. Gerard MSc, PGDipLaw, PGDipBar, FCIOB, MCIArb, MAE