Delay vs prolongation – what can actually be claimed
Delay and prolongation are often confused, but the distinction is critical. Delay concerns completion dates; prolongation concerns recovery of time-related costs for extended duration.
The distinction (why it matters)
Delay and prolongation are often used interchangeably on projects, but they are not the same. The distinction is critical because time and money are recovered through different contract mechanisms and evidential routes.
- Delay: the effect on completion dates (time outcome).
- Prolongation: recovery of time-related costs from extended duration (cost outcome).
- Separating them: improves clarity, credibility, and negotiation outcomes.
What “delay” actually refers to
Delay refers to the effect on completion dates. It is about whether an event pushes a contractual completion date, milestone, or key date — and how that is shown through programme logic.
Think of delay as a programme question
The core issue is: did the event affect the critical path (or relevant completion logic) and change the completion outcome? Without programme impact, “delay” becomes harder to sustain.
What “prolongation” actually refers to
Prolongation relates to the recovery of time-related costs arising from extended project duration. In simple terms: if the project lasts longer because of a relevant event, what additional time-dependent costs does the contractor incur?
Time-related preliminaries
Site management, supervision, welfare, temporary services and other time-dependent overheads.
Extended site overheads
Ongoing site costs that only arise because the duration extends (not because scope increases).
What must be proved to recover prolongation costs
To recover prolongation costs, contractors must demonstrate causation, programme impact, and entitlement under the contract. This means connecting the event to the extended duration, then connecting the extended duration to the time-related cost consequences.
Entitlement
The contract must support recovery for the relevant event type and route (notice, assessment, variation/CE etc.).
Causation + programme impact
Demonstrate that the event caused an extension to completion logic, not simply disruption without duration impact.
Time-related cost consequence
Show the additional costs arise from the extended duration (not from general inefficiency or scope growth).
Proportionate substantiation
Keep records aligned to the claim heads and period — enough to prove the point, without noise.
Why clear separation wins
Clear separation of time and cost effects improves credibility and outcomes. It helps the reviewer see: (1) whether completion is affected, and (2) what time-related costs genuinely arise from the extended duration.
FAQs
Can you have prolongation costs without “delay”?
You can incur additional costs through disruption or inefficiency without a completion-date change, but “prolongation” (time-related costs from extended duration) typically depends on demonstrating an extension to duration under the contract logic.
Why do prolongation claims often fail?
Common reasons include unclear entitlement, weak programme impact, poor causation links, and presenting cost items that do not clearly arise from extended duration.
What is the simplest way to improve credibility?
Separate the time story from the cost story: show the programme impact first, then quantify only the time-related costs that arise from the extended duration and period affected.
Next steps
If you need to clarify whether you have delay, prolongation, or both — and what can actually be recovered — we can help you build a contract-led, programme-supported position with proportionate substantiation.