Why does an extension of time matter?
If you finish late without an extension of time, you are in breach of contract, and the contractor can claim the losses the delay caused it, or liquidated damages if your subcontract provides for them. An extension of time moves your completion date for delays that are not your responsibility, such as late access, late information, variations or delay by other trades.
An extension of time does not, on its own, pay you for the delay. The cost of delay is recovered as loss and expense, which usually needs its own notice. Time and money are separate entitlements: notify both.
When should I give a delay notice?
As soon as it becomes reasonably apparent that your work is being, or is likely to be, delayed. Most JCT subcontracts require notice “forthwith”, and contractors’ own terms often set shorter periods. Do not wait until you can work out the full effect. Notify, then update.
What should a delay notice say?
- what has happened, where and when, and who is responsible for it;
- which events you rely on, using your contract’s terms, such as “Relevant Event”;
- which of your activities are affected, and how;
- what you need from others to reduce the delay, such as access, information or removal of obstructions; and
- your estimate of the effect on your completion date, or when you will give it.
Head it clearly as a notice under the contract, send it to the person and address the notices clause requires, and keep proof that it arrived. Then give further particulars and updated estimates while the delay continues, and say when it ends. Write calmly and stick to facts: “we were prevented from starting level 2 by the incomplete roof” is far stronger than “we are in delay on level 2”.
Is notice a condition precedent?
Sometimes. A clause that says an extension will only be granted if notice is given by a certain time, or that uses words such as “condition precedent”, “provided that” or “failing which”, may bar your claim if you miss the deadline. Courts enforce such clauses where the wording is clear. Other clauses simply require notice, and missing it is a breach that may reduce your entitlement but does not remove it. Read your clause before the job starts and diarise any time limits.
The contractor’s review after completion
Many JCT subcontracts require the contractor, within a set period after practical completion of the subcontract works (often 16 weeks), to review the completion date and fix the extension that is fair and reasonable, taking account of relevant events whether or not they were specifically notified. Check your clause. That review is a safety net, not a substitute for notices: an adjudicator will look first at what you told the contractor at the time.
What if the contractor caused the delay but will not extend?
Under the prevention principle, a party cannot hold the other to a completion date that it has itself prevented from being met. Where the contract allows time to be extended for the contractor’s own acts and the contractor refuses, an adjudicator can decide what extension should have been given. Where the contract has no way of extending time for the contractor’s delay, time may become “at large”: you must then complete within a reasonable time, and the contractor cannot claim damages for that delay.
The prevention principle gives way to clear express terms. In North Midland Building Ltd v Cyden Homes Ltd [2018] EWCA Civ 1744 the Court of Appeal upheld a clause that excluded extensions for concurrent delay. The wording of your contract matters.
What is concurrent delay?
Concurrent delay is where two causes of delay operate at the same time, one your responsibility and one the contractor’s. The answer depends on the contract. Some contracts allow an extension for the contractor’s delay even though you were also late; others do not. Take advice before accepting, in writing or in a meeting, that any delay was concurrent.
Can the contractor make me accelerate?
Most subcontracts require you to use your best endeavours, or reasonable endeavours, to prevent delay. That usually means managing your work sensibly, for example by rearranging activities. It does not normally oblige you to add labour or work weekends at your own cost to recover delay caused by others. Unless your contract allows the contractor to instruct acceleration, it needs your agreement.
If you are asked to accelerate, agree the price in writing before you incur the cost if you possibly can. If you must comply at once, do so under protest, say that you will claim the cost, and record the additional resources every day. Longer hours and larger gangs usually lower output per hour, so acceleration costs more than the extra wages.
Records
An extension of time claim is only as good as the records behind it: dated notices, programmes, progress records, diaries and photographs that show when each area was available to you and what stopped you. Record the progress of the building and other trades as well as your own work. See our guide to site records.
Questions
Is it too late to ask for an extension of time after completion?
Not necessarily. Many contracts require the contractor to review the completion date after practical completion, taking account of events whether or not they were notified, and an adjudicator can decide what the extension should be. Late notice can weaken your position, though, especially where the contract makes notice a condition.
Does an extension of time mean I get paid for the delay?
No. Time and money are separate. The cost of delay is recovered as loss and expense, which usually needs its own notice and supporting information.
What is a Relevant Event?
The JCT term for an event that entitles a contractor or subcontractor to an extension of time, such as a variation, late information or an act of prevention by the other party. Other contracts use different terms.
Do weekly reports count as delay notices?
They may help as evidence, but do not rely on them. Give a separate written notice that meets your contract’s requirements.
General guidance on the law of England and Wales, not legal advice. Last reviewed 2 November 2026.