Concurrent delay occurs when two or more delay events affect the critical path at the same time — one being the responsibility of the employer and the other the responsibility of the contractor.
Under English law (following the City Inn v Shepherd Construction decision and the SCL Protocol), where there is a true concurrent delay, the contractor is generally entitled to an extension of time but not to additional costs. However, the position varies by jurisdiction and contract form.
The key challenge in concurrent delay is establishing whether the delays are genuinely concurrent (affecting the same critical path activities at the same time) or merely parallel (occurring at the same time but affecting different parts of the programme). Robust programme analysis using the windows method is typically required to distinguish between the two.
Under FIDIC 2017, Clause 8.5 does not explicitly address concurrency. Under NEC4, the "first notified" approach may apply. Under JCT, the Malmaison principle generally applies — the contractor receives time but not money for concurrent delays.