Prolongation Cost

A construction project runs beyond the planned finish, so site supervision, temporary facilities and hired equipment may have to remain longer, and their extra time-related cost is often called prolongation cost. Not every expense on a late project is a prolongation cost, because rework, disrupted productivity and price increases can raise different questions, so separate them in the cost records to avoid double counting.

The Society of Construction Law publishes a Delay and Disruption Protocol for assessing delay and financial consequences that emphasises records and analysis, although the protocol is guidance, not a replacement for the parties' contract or governing law. The starting point is to establish what changed the completion date, since an owner instruction, design information, weather event or contractor delay may have different contractual effects, and a programme update helps connect the event to the affected work.

An extension of time and payment for prolongation are separate questions, and Norton Rose Fulbright explains that time does not automatically equal money, so a party may gain more time without proving a compensable cost claim. A fictional bridge team that receives an extension after unusually severe weather reviews the contract before claiming site overheads, because the extension itself does not decide who pays.

A baseline schedule gives a reference, but actual progress matters, so update it during the job, including critical activities and mitigation steps, since rebuilding the story months later is harder. Keep invoices, payroll, equipment logs and site diaries, allocate costs to the extended period and remove costs that would have arisen anyway, and show both the amount and its connection to the delay.

A fictional contractor's site office that remains open for two extra months tracks rent and documented utilities rather than assuming a flat monthly rate is recoverable, and a fictional electrical contractor billing a crane uses equipment records showing when it stayed and whether it served other work, not the original hire budget alone. A simple estimate multiplies extra months by average monthly time-related costs, which is useful for forecasting, whereas a claim may need evidence of actual costs and contractually accepted valuation methods instead.

Pinsent Masons discusses causation, records and methods for assessing prolongation costs in construction disputes, and treatment can differ between jurisdictions and contract forms, so do not present one formula as universal law. Head-office overheads are especially contested, as the business may need to show how an extended project affected its capacity or actual overhead recovery, and a generic percentage may not be persuasive.

Notice provisions can set short deadlines, so record potential delay events and send notices as the contract requires, because missing a notice may complicate recovery even if the extra expense is real. Concurrent delays require care, since if separate events overlap, entitlement can depend on the contract and the analysis of their effects, and the entire extension should not be attributed to one party without examining the timeline.

A contractor may mitigate by resequencing work or returning rented equipment early, and the cost record should show sensible steps taken, although mitigation does not mean the contractor must absorb every compensable expense. Claims should identify each delay event, affected period and cost category, since a transparent calculation makes discussion easier and helps reveal overlapping claims for the same staff or equipment, as when a fictional hospital project logs a late design change and a separate contractor staffing issue and checks which activities each delayed rather than combining the two periods.

Cash forecasting matters while entitlement is unresolved, so continue paying staff and suppliers even when a claim is being prepared and do not book disputed compensation as certain cash. A final settlement may differ from the original estimate because contractual risk allocation, evidence and negotiation all matter, so seek project and legal advice for a live dispute; prolongation cost is a useful label for time-related expense, not a shortcut to recovery, and good schedules, notices and cost records turn a broad complaint into an assessable claim.