Template

Prolongation Claim Template: A Sample Letter You Can Adapt

Last updated July 2026 · 10 min read

The Extension of Time has been granted. The daily reports, hire invoices, and allocation sheets are finally sorted into a folder. Now comes the part nobody teaches on Site: writing the actual letter that puts the cost claim in front of the Engineer. This guide gives you that letter — a prolongation claim template you can adapt — and the rules that keep it from being sent back for particulars.

The Prolongation Claim Letter vs the Delay Notice — Don't Confuse Them

Two different letters get written during a prolongation claim, and mixing them up is how a strong claim gets weakened before it even reaches the numbers.

The first is the initial notice — the fast alarm sent under Sub-Clause 20.1 within 28 days of the Contractor becoming aware of the delay event. It names the clause, states the event happened, and reserves the right to an Extension of Time and Cost. It contains no figures.

The second is the prolongation claim letter — the detailed submission that follows. This is where the heads of cost, the assessment period, and the supporting evidence are set out and quantified. If the initial notice has not gone out yet, stop here and send that first — a prolongation claim letter cannot repair a notice that was never served.

💡

Key Takeaway: The initial notice is the fast, figure-free alarm due within 28 days of awareness. The prolongation claim letter is the detailed submission that follows, carrying the cost figures and evidence. Send the notice first — the claim letter cannot substitute for it.

What a Prolongation Claim Letter Must Contain

A prolongation claim letter is a covering letter, not the evidence bundle itself. It should be short enough to read in two minutes, with every figure traceable to an enclosure. The parts that make it hold up:

Reference to the notice already served — the date and clause of the original notice, so the letter is clearly linked to a live entitlement, not a new claim out of nowhere.
The clause carrying the Cost entitlement — the specific cause clause, plus Sub-Clause 20.1.
The assessment period — the dates during which the delay event actually had effect on the critical path, not the tail end of the programme.
Cost by head, summarised — site overheads, site staff, plant, accommodation, head-office overhead, and finance, each with a total, referencing the detailed enclosure.
The particulars deadline met — a statement that this submission is made within the contractual period following the notice.
The enclosures list — programme analysis, timesheets, invoices, and the heads-of-cost workings, indexed so each figure can be checked.

Notice what belongs in the annex, not the letter: the line-by-line invoice detail, the daily reports, and the full formula workings for head-office overhead. Cramming all of that into the letter body buries the argument the Engineer actually needs to follow.

💡

Key Takeaway: Six parts make a strong prolongation claim letter — the notice reference, the Cost clause, the assessment period, the cost summarised by head, confirmation the deadline is met, and an indexed enclosures list. The detail lives in the annex, not the letter.

Prolongation Claim Letter Template — Copy and Adapt

Here is a skeleton for the covering letter. Replace everything in square brackets with your own facts, then delete the brackets. Attach the detailed cost workings and evidence as a separate enclosure rather than folding them into the letter itself.

[Date] To: [Engineer's name and company] Project: [Project name and contract reference] Prolongation Claim under Sub-Clause [X.X] and Sub-Clause 20.1 — Reference: Notice of [date of original notice] Further to the Contractor's notice dated [date], given under Sub-Clause [X.X] of the Conditions of Contract, the Contractor submits the following particulars of its prolongation cost claim. The event has affected the Works for the period [start date] to [end date], being the period during which the delay had effect on the critical path, as shown in the enclosed programme analysis (Enclosure [1]). The cost incurred during this period, by head, is as follows: site overheads [amount], site staff [amount], plant and equipment [amount], accommodation and facilities [amount], head-office overhead [amount, basis stated], [finance, if applicable]. Total claimed: [amount]. This submission is made within [42] days of the notice referred to above, in accordance with the Contract. Supporting records are enclosed as follows: [list of enclosures — programme analysis, timesheets, hire invoices, accommodation costs, overhead calculation]. The Contractor reserves its right to submit further particulars should additional cost be incurred or identified. Yours faithfully, [Name] [Designation, for the Contractor]

Three warnings on the placeholders. First, "[42] days" is the FIDIC 1999 default for particulars — the FIDIC 2017 Second Edition uses 84 days, and a bespoke contract may set its own figure; use whichever actually governs. Second, the heads of cost and how to calculate each one are covered in full in the companion guide on prolongation cost claims — this letter is the wrapper, not the calculation. Third, keep the amounts as summary totals here; the working detail belongs in the enclosures.

💡

Key Takeaway: The letter references the notice, states the assessment period, summarises cost by head, confirms the particulars deadline, and lists enclosures. Use the contract's actual particulars period — 42 days is only the FIDIC 1999 default, and 2017 uses 84.

Worked Example: A Filled-In Prolongation Claim Letter

Here is the same template filled in for an Unforeseen Physical Conditions event — unexpected rock strata that delayed excavation and kept the Contractor's team and plant on Site for an extra five weeks.

26 April 2026 To: Ms L. Vance, Resident Engineer, Vance & Partners Project: Northgate Interchange — Contract NGI-2024-11 Prolongation Claim under Sub-Clause 4.12 and Sub-Clause 20.1 — Reference: Notice of 17 March 2026 Further to the Contractor's notice dated 17 March 2026, given under Sub-Clause 4.12 of the Conditions of Contract, the Contractor submits the following particulars of its prolongation cost claim. The event has affected the Works for the period 17 March 2026 to 21 April 2026, being the period during which the delay had effect on the critical path, as shown in the enclosed programme analysis (Enclosure 1). The cost incurred during this period, by head, is as follows: site overheads USD 38,400, site staff USD 52,900, plant and equipment USD 61,200, accommodation and facilities USD 11,700, head-office overhead USD 9,850 (actual basis, per Enclosure 5). Total claimed: USD 174,050. This submission is made 40 days after the notice referred to above, within the 42-day particulars period, in accordance with the Contract. Supporting records are enclosed as follows: programme analysis (Enclosure 1), daily site reports (Enclosure 2), plant hire invoices (Enclosure 3), accommodation invoices (Enclosure 4), head-office overhead calculation (Enclosure 5). The Contractor reserves its right to submit further particulars should additional cost be incurred or identified. Yours faithfully, R. Demir Contracts Manager, for the Contractor

That is the whole covering letter. It names the clause, fixes the period, gives the totals by head, confirms the deadline, and points to exactly where the proof sits. The arguing happens in the enclosures, not in adjectives.

💡

Key Takeaway: A strong prolongation claim letter is short and factual — clause, period, totals by head, deadline confirmation, and an enclosures list. Let the annex carry the proof instead of arguing the case in the letter itself.

Which Clauses Actually Give You a Cost Entitlement

Not every delay carries a prolongation cost claim. Under the FIDIC 1999 Red Book, whether Cost is available at all depends entirely on the cause clause:

Weather Delay — exceptionally adverse climatic conditions, Sub-Clause 8.4(c). Time only. There is no prolongation claim to write here.
Variation — instructed changes to the Works, Clause 13. Time and Cost, running from the date of the instruction rather than awareness.
Unforeseen Physical Conditions — sub-surface or hydrological conditions a competent Contractor could not have foreseen, Sub-Clause 4.12. Time and Cost, but no profit.
Access to Site — failure to give possession or right of access, Sub-Clause 2.1. Time, Cost, and reasonable profit.
Delayed Drawings — late issue of drawings or instructions by the Engineer, Sub-Clause 1.9. Time, Cost, and reasonable profit.

This is why the first check, before drafting any prolongation claim letter, is confirming the cause clause actually carries Cost. Writing a detailed cost submission against a Weather Delay notice is wasted effort — the entitlement for time was already the whole of it.

💡

Key Takeaway: Cost follows the cause clause, not the fact of delay. Weather (8.4(c)) gives time only. Variations, Unforeseen Conditions, Access to Site, and Delayed Drawings all carry Cost — with profit available under 2.1 and 1.9 but not under 4.12.

Common Mistakes in Prolongation Claim Letters

Most prolongation claim letters that get picked apart fail for a small set of avoidable reasons:

No reference to the original notice. A cost claim that does not link back to a served notice reads as a fresh claim, inviting a time-bar challenge on the notice itself.
Wrong deadline stated. Writing the 28-day notice figure where the 42-day (or 84-day, under 2017) particulars period belongs is a fundamental error that exposes the claim procedurally.
Cost calculated on the preliminaries rate. The tender rate prices the work; it does not prove what the delay actually cost. Engineers reject this on sight.
Wrong assessment window. Claiming the overrun at the tail of the programme instead of the period the event actually affected the critical path.
Figures with no enclosure reference. A total with nothing traceable behind it is an assertion, not a claim.
Cost claimed against a time-only clause. Submitting a prolongation claim tied to a Weather Delay notice under 8.4(c), which carries no Cost entitlement at all.

Every one of these is a structural mistake, not a factual weakness — which means every one of them is avoidable with a template that prompts for the right parts in the right order.

💡

Key Takeaway: Claims fail for missing notice references, swapped deadlines, rate-based costing, the wrong assessment window, untraceable figures, and Cost claimed against a time-only clause. All six are structural and avoidable.

Frequently Asked Questions

Is a prolongation claim letter the same as the initial delay notice?

No, and confusing the two is a common mistake. The initial notice is the fast alarm sent within 28 days of awareness under FIDIC 1999, reserving the right to Cost. The prolongation claim letter is the detailed particulars that follow, setting out the heads of cost, the assessment period, and the evidence. The notice opens the claim; the prolongation claim letter proves it.

What deadline applies to a prolongation claim letter?

The particulars deadline, not the notice deadline. Under FIDIC 1999 this is 42 days from the initial notice; under the FIDIC 2017 Second Edition it is 84 days. If a bespoke contract sets a different period, use that figure instead. Writing the 28-day notice deadline into a prolongation claim letter is a common and serious error.

Does every FIDIC delay clause support a prolongation claim?

No. Cost only follows if the underlying cause clause grants it. Exceptionally adverse climatic conditions under Sub-Clause 8.4(c) give an Extension of Time only, with no Cost. Variations (Clause 13), Unforeseen Physical Conditions (Sub-Clause 4.12), Access to Site (Sub-Clause 2.1), and Delayed Drawings (Sub-Clause 1.9) all carry a Cost entitlement, which is what makes a prolongation claim possible.

Should the prolongation claim letter itself contain all the cost figures?

The letter should summarise the entitlement, the period, and the total by head, then reference a detailed enclosure. Programme analysis, timesheets, invoices, and the heads-of-cost workings belong in an indexed annex, not buried in the letter's body. Keep the letter itself short and let the annex carry the proof.

Authoritative Sources

This guide reflects the FIDIC Conditions of Contract and established construction-law authority. For the primary materials, see:

FIDIC Conditions of Contract — the official contract suite published by the International Federation of Consulting Engineers, which sets out the Sub-Clause 20.1 claims procedure and the Cost provisions of the cause clauses.
SCL Delay and Disruption Protocol — the Society of Construction Law's protocol on assessing prolongation cost against the period the delay event actually had effect.

About the Author

Muhammad M. Jiwani is a Project Director with 15 years' experience on major infrastructure and energy projects administered under FIDIC contracts. He writes from first-hand experience serving notices and managing contractual claims on live projects.

Write a watertight notice, every time.

Get Started