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Site diary evidence for delay and extension of time claims

When a project overruns, the party with the better records usually has the better argument. Here is what your diary needs to show, and where claims fall apart.

Written for UK contractors · Updated October 2026

Why delay claims turn on records

When a project overruns, the question is who caused the delay and what it cost. A contractor asking for more time, or for money to cover prolongation, has to show the delay happened, what caused it, and that it affected the work. The other side will test each of those points.

The strongest evidence is what was written down at the time. Records made on the day, by someone who was there, are more believable than a reconstruction months later. That is where a good site diary earns its keep.

Notice comes first

Most construction contracts, including the common standard forms, set out how and when you must give notice of delay or change. Some treat late notice as a reason to refuse the claim. Read the notice clause in your contract before you need it, and put the deadlines somewhere your site team will see them.

The diary does not replace formal notice, but it helps you decide when to give it. If the diary shows that a delay started on a given day, you know when the clock began.

What the diary needs to show

• The event. What happened, on what date and at what time, and who was told.
• The cause. Late information, a late instruction, access not available, a change, weather, a supplier failure or your own issue. Be precise and fair.
• The effect. Which activities stopped or slowed, how many people and how much plant stood idle, and for how long.
• Weather. Conditions and the hours lost. Weather claims depend on how bad it was compared with what would normally be expected, so record it daily, including the normal days.
• Instructions. Written and verbal, with who gave them and when. If it was verbal, say you asked for it in writing.
• Labour and plant. Who and what was on site each day, since idle resources are what costs money.
• Photos. Dated and showing the state of the work, the area affected or the thing that stopped you.
• Correspondence. Reference the emails, requests for information and notices sent, with their dates.

Where the evidence falls apart

• Blame without detail. "Client delays again" proves nothing. Give the date, the item, the request and the response.
• Missing days. An unexplained gap during the disputed period invites doubt about the entries around it.
• Records written to suit the claim. Entries that read as if written for a lawyer, or that appear in a different style once a dispute starts, damage credibility.
• No separation of causes. If your own late materials overlap with the client's late drawings, the diary should show both honestly. Claims that ignore your own delay are easily picked apart.
• No link to the programme. A delay matters only if it affected the critical path. Say which activity was held up.
• Records that can be changed with no trail. A system that logs edits is more credible than one that does not.

Getting the records out when you need them

When a claim is being prepared, someone has to find every relevant entry, photo and instruction across months of site work, often for several sites. That is slow with paper diaries in vans and photos scattered across phones. Searchable, dated records that can be exported as PDFs, with the photos inside them, turn weeks of searching into hours.

The free 3-minute assessment asks what would happen if you had to go back to your diary after a dispute, and gives you a report on the gaps.

This guide is general information for contractors, not legal advice. Notice and claim rules depend on your contract, so take advice from a solicitor or a quantity surveyor before relying on it for a claim.