Stage payments for an extension or renovation
By Alex Williams, director of Ty Parc Construction, a building contractor in Newport, South Wales · Last reviewed 21 October 2026
Pay a builder in stages as work is finished, not by date and not mostly upfront. A common pattern is a 10% deposit, then payments at foundations, walls and roof structure, roof and windows, first fix and second fix, with about 10% left until the job is finished and snagged. A deposit above 25% is a warning sign. Build your own schedule with the free tool below.
Build my payment schedule — freeA typical schedule
| Stage | When it’s due | Share |
|---|---|---|
| Deposit | On signing | 10% |
| Foundations | Foundations complete and signed off by building control | 15% |
| Walls and roof structure | Walls to plate level and roof structure up | 20% |
| Roof and windows | Roof covered, windows in | 15% |
| First fix | First fix plumbing and electrics, plastering | 15% |
| Second fix | Second fix and decoration | 15% |
| Completion | Job complete and snags fixed | 10% |
One published UK example (Planning Signal, reviewed April 2026). Simple jobs need fewer stages; your contract should say what triggers each one.
How much deposit is fair?
10–15% is common. It covers booking your slot and early materials. Be wary of anything above 25%. For bespoke items ordered early, such as windows or a kitchen, a separate materials payment against an invoice is reasonable.
Holding money back until snagging
There are two common ways to do it:
- Hold the final 10% until the snags are fixed.
- Hold 5% of each payment, and release half at completion and half after a 6–12 month defects period.
Agree it in writing at the start. “Retention” is being banned in commercial construction contracts by the Commercial Payments Bill, but that’s aimed at business contracts — on a home job, an agreed holdback is still normal.
What triggers a payment
- Define each stage by something you can see (“roof felted and battened”), not a date.
- The builder asks for payment when a stage is done.
- You check and pay within the agreed number of days.
- If something’s not right, say what and pay the part that’s agreed.
Extras change the schedule
When an extra is agreed, agree when it’s paid — usually with the next stage. Keep a running total so the last payment isn’t a surprise. Credits for work taken out come off the total too. At the end, the final account brings it all together.
Builders: setting your schedule
Front-load only what covers materials you’ve genuinely committed to. Make every stage something the client can see, and send the schedule with the quote. Put it in a written contract — see JCT, FMB and simple building contracts — and if a stage payment goes unpaid, see the letter before action guide.