You finish a job three months late, not through any fault of your own. The main contractor held your access, changed the scope, redesigned the details mid-build, and your men stood around waiting. Now you want to recover your prolongation costs — and the MC says it's your problem.
Here is the hard truth: without the right records, you probably cannot prove it. Not because you were wrong, but because you did not record it properly at the time.
This is the most common commercial failure in construction. Here is what to do instead.
Why records matter more than anything else
A delay claim is essentially a factual argument: the works were delayed, the cause of delay was the employer's/MC's act or default, and you incurred additional costs as a result. Every word of that sentence requires evidence.
Adjudicators and arbitrators see hundreds of delay claims. The ones that succeed have one thing in common: a contemporaneous record of what happened, who was responsible, and what it cost — written at the time, not reconstructed afterwards.
Reconstructed records are unconvincing. A site diary written six months after the event looks like a site diary written six months after the event.
The five records you need from the first week
1. A properly baselined programme
You cannot prove delay if you cannot prove what the original programme was. Your subcontract programme — accepted by the MC — is your baseline. Keep a copy. If it changes, document why, what was agreed, and who agreed it. If the MC imposes a revised programme without your agreement, write to them and say you are not accepting the revised dates as your contractual completion.
The baseline programme must show: activity durations, sequence logic, the critical path, start and finish dates, and any key dependency on the MC for access or information.
2. Daily site diaries — every single day
Your site manager or foreman should complete a site diary every working day. It should record:
- Labour on site by trade (your own and any mates/gangsmen)
- Plant on site
- What work was carried out
- Any areas or activities that could not proceed — and why
- Instructions received (verbal or written)
- Visitors to site (MC's site manager, clerk of works, designers)
- Weather (relevant for external works)
- Any safety incidents or near-misses
This diary is worth its weight in gold in a dispute. Do not delegate it to whoever is on site that day without checking it is being done properly.
3. Written notices — every time
Under most JCT and NEC subcontracts, you have a time limit to give notice of delay events. Under NEC, this is 8 weeks from becoming aware of a compensation event — miss it and you typically lose the entitlement. Under JCT, notice requirements are less strict but still important.
If in doubt, give notice. There is no downside to giving a written notice that turns out to be unnecessary. There is a very significant downside to failing to give notice and losing your entitlement entirely.
Notices should state: the event causing or likely to cause delay, the effect on your programme, and a request for an extension of time. Email is fine — make sure you have a paper trail.
4. Record access obstructions precisely
If you cannot access your work area, record it. Every day. With photos where possible.
Common MC obstructions: structural steelwork not complete, preceding trades still in area, temporary works still in place, services not diverted. None of these are your fault — but you must prove they happened, on which dates, affecting which activities.
A simple spreadsheet logging: date, area, obstruction, cause (MC/other trade/design issue), number of operatives affected, hours lost — is extremely powerful in a claim.
5. Capture your additional costs in real time
Prolongation cost is the additional cost of being on site longer than planned. The key heads of cost are typically: site management and supervision (weekly cost × additional weeks), plant standing time, welfare and accommodation, extended temporary services, increased insurance premiums.
Keep time sheets for supervisors, plant hire invoices, accommodation costs, and any additional insurance premiums. Do not throw away hire receipts or time records because "the job's done." They are the evidence for your claim.
Weekly claim records checklist
What happens without records
Without these records, your claim will look like this: "We were delayed by the MC. We lost money. Here is a number." That is not a claim. That is a request.
The MC's QS will reject it. If you go to adjudication, the adjudicator will reject it. You will spend thousands on legal fees and recover nothing.
With the right records, the same claim looks like this: a programme demonstrating the baseline; a delay analysis showing which events caused delay and when; a contemporaneous record of obstructions; notices given at the time; and a cost analysis linked directly to the delay events. That is a claim that gets paid.
Getting help with your subcontract
Most of the disputes we see could have been avoided with a proper subcontract review before signing. Timebar clauses, unilateral programme revision rights, onerous notice requirements — these all need to be understood before the job starts, not when things go wrong.
Get your subcontract reviewed before you sign
We review JCT and NEC subcontracts, identify the clauses that put you at risk, and tell you what to push back on. Fixed fee: £100. Delivered in 24 hours.
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