Prolongation Cost
The time-related cost of remaining on site longer than planned — site establishment, supervision, plant on hire, preliminaries. It is claimed separately from an extension of time, and it is the money half of a delay claim.
An extension of time buys you relief from liquidated damages. It does not put a dirham in your account. Prolongation cost is the claim that does — and it must be proved as actual cost incurred during the extended period, not as a percentage of anything.
The recurring failure is the one that costs most: a contractor wins the EOT, celebrates, and never makes the money claim — or makes it late, on a formula, with no cost records tying spend to the extended period. The cost records had to exist at the time. They cannot be assembled afterwards, and a tribunal can tell when they have been.
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