Delay
The prevention principle
The prevention principle is often reached for and rarely understood. It is a rule that operates through the contract, not a solvent for every notice failure.
- Jurisdiction
- England and Wales, with comparative notes
- Law and editions as at
- 3 August 2026
- Last reviewed
- 3 August 2026
- Editorial status
- Editorial draft, not yet independently reviewed
The idea
A party generally cannot insist on an obligation whose performance it has itself prevented. Applied to construction, if an employer causes delay and the contract provides no machinery to extend time for it, time may be set at large: the contractor’s obligation becomes to complete within a reasonable time, and the liquidated damages mechanism can fall away with the fixed date it was attached to.
Why it rarely bites on a standard form
Judgment Multiplex Constructions (UK) Ltd v Honeywell Control Systems Ltd (No 2) [2007] EWHC 447 (TCC) is the core explainer in England and Wales: effective extension-of-time machinery is precisely what prevents time being set at large, because the contract already provides a route to deal with employer-caused delay.
Standard forms are written with that in mind. Their Relevant Event and compensation event lists exist to keep the completion date operable when the employer causes delay. The principle therefore matters most where the machinery has been amended into ineffectiveness, or where a notice condition is drafted so that employer delay can fall outside it entirely.
Express allocation is given effect
Judgment North Midland Building Ltd v Cyden Homes Ltd [2018] EWCA Civ 1744 shows that where the parties expressly allocate the consequences of concurrent contractor delay, the prevention principle does not override that bargain.
What it is not
- It is not a cure for a missed notice where the contract makes notice a condition of entitlement.
- It is not a route to compensation. Time at large is about the date and the damages, not about payment.
- It is not a general fairness discretion, and arguments that treat it as one tend to fail.
Other jurisdictions
Australian authority on prevention and extension-of-time discretion turns closely on drafting, and the position varies by state and by clause. In civil-code systems the same commercial problem is usually approached through good faith, creditor contribution or code provisions on compensation rather than through a common-law principle of this name.
Where the record comes in
Every mechanism on this page turns on evidence: what happened, what was known and when. A record built as the job happens is worth more than any argument assembled afterwards. Construction Metric keeps that record automatically, from the messages, photographs and voice notes a site team already sends.
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The analysis on this site is only as fast as the evidence behind it. AI Metric builds bespoke systems for consultancies, contractors and claims teams: document and correspondence triage, event registers assembled from the project record, programme and cost reconciliation, and drafting support that always cites the document it came from. Built for review by your own experts, never to replace their judgement.
Do not overread this page
Whether time is at large on any project depends on the exact wording, the facts and the governing law. The cases named are summarised, not analysed, and this page is not a view on any of them.
General explanation of how contract mechanisms, analysis methods and legal principles generally work. It is not legal or contractual advice, not an opinion on any project, and no standard-form contract wording is reproduced anywhere on this site. Standard forms are routinely amended, so every default described here, including every time period, can be different on your project. Your executed contract, as amended, and the governing law and forum always control. Deadlines may already be running: if an event has occurred, preserve your position and take qualified advice.