Delay, disruption and prolongation

A delay affects progress of the works. A critical path delay affects the date of practical completion. Delay may be distinguished from disruption, which affects the efficiency and progress of the works (such as the method of delivery) but not the date of practical completion.

Usually only critical path delays result in a contractual right to an extension of time. For example, a one day strike which stops a job would cause a delay. By contrast, an example of disruption costs might be the additional expenses and resources required when works are rescheduled.

The law does not distinguish between prolongation costs and delay costs.