JCT, FMB or a simple written agreement: which contract for a home building job?
By Alex Williams, director of Ty Parc Construction, a building contractor in Newport, South Wales · Last reviewed 21 October 2026
For most home jobs without an architect, the JCT Homeowner Contract or the FMB contract is enough. If an architect or surveyor is running the job, JCT Minor Works is the usual choice. A builder’s own written quote can work for small jobs, but only if it covers price, payments, extras and defects in writing. Whatever you use, the arguments almost always come from the same place: extras and payments that were agreed on site and never written down.
The options at a glance
| Contract | Best for | Who runs it | Cost | Watch out for |
|---|---|---|---|---|
| JCT Homeowner Contract | Homeowners hiring a builder directly, smaller jobs | You and the builder (versions with or without a consultant) | Low (buy from JCT) | Keep the payment schedule and extras clause filled in properly |
| JCT Minor Works (MW / MWD 2024) | Extensions, lofts and renovations up to roughly £250,000 with an architect or contract administrator | A contract administrator | About £40–£60 for the form | Needs someone to administer it — valuations, instructions, certificates |
| FMB Domestic Building Contract | Jobs with a Federation of Master Builders member | The builder (FMB members) | Through the FMB member | Ask about the warranty and the FMB’s dispute service |
| Builder’s own terms or a detailed quote | Small, simple jobs | The builder | Free | Often written for the builder — check it covers the points below |
| Bespoke contract | Unusual or high-value work | A solicitor | Solicitor’s fees | Cost and time |
Prices and editions change — check the current version on the publisher’s site before you buy.
What any contract should cover
- The exact scope and drawings.
- The price and whether it’s fixed.
- What’s excluded.
- The payment stages and what triggers each one.
- How extras and changes are priced and agreed — in writing, before the work.
- Start and finish dates and what happens if they slip.
- The defects period and any amount held back until then.
- Insurance.
- Who gets building control sign-off.
- How disputes are handled.
- If the builder signs you up at your home or online, your 14-day cancellation rights.
Payment stages and deposits
Pay against stages that are finished, not dates. A deposit of 10–15% is common; more than 25% is a warning sign. Hold back a small amount until snagging is done. (A full guide to stage payments is coming soon.)
Extras: the clause that causes most arguments
An extra (a “variation”) is any change to the work you agreed at the start — something added, swapped or done differently. Agree the price and any effect on the finish date in writing before the work is done, not after. When work is taken out, record the credit the same way, so the final figure goes down as well as up.
Does the Construction Act apply to my home job?
Usually not in full. Its payment notice and adjudication rules generally don’t apply to contracts with a “residential occupier” — someone having work done on the home they live in or intend to live in. The Court of Appeal considered this in RBH Building Contractors Ltd v James [2026] EWCA Civ 511. Some contracts (including some JCT forms) build in their own payment and dispute steps, so read yours. If it matters to you, take advice.
Builders: which should you offer?
Having a standard contract you use on every job looks professional and saves arguments. Whichever you use, keep extras and payments agreed in writing as the job goes — and if a client still won’t pay at the end, see our guide to the letter before action and the free letter generator.