Quick Answer
Yes — you should always have a written contract with a builder in 2026, even for smaller jobs. A contract protects you if work is substandard, if prices are changed without agreement, or if the builder abandons the project. For larger projects, consider a JCT Minor Works contract.
Hiring a builder for an extension, renovation, or major refurbishment is one of the largest financial decisions most UK homeowners make. In 2026, having a clear written contract is the single most effective protection against disputes, overcharging, and poor workmanship. This guide explains why contracts matter, what they should include, and what to do if a builder refuses to provide one.
In this guide
Why Contracts Matter
Building disputes are one of the most common forms of consumer complaint in the UK. The vast majority arise from the same root cause: vague or verbal agreements that leave scope, price, and standards open to interpretation. A written contract does not prevent all disputes — but it means any dispute is resolvable, because there is a clear record of what was agreed.
Specifically, a contract protects you when:
- The builder changes the price mid-project without your written agreement
- Work is not completed to the specification or quality you expected
- The project overruns significantly with no explanation or remedy
- The builder abandons the project after receiving payments
- Defects appear after completion and the builder disputes responsibility
A contract also benefits the builder — it is clear evidence of what they were paid to do, which protects them from unreasonable demands. Professional builders generally welcome contracts for exactly this reason.
What a Good Contract Should Include
Every building contract should address these key areas. For large projects (over £30,000), a formal JCT contract is recommended. For smaller projects, a detailed letter or email confirmation covering these points is often sufficient:
Types of Contract
JCT Minor Works Building Contract
The industry standard for residential building projects. Covers all key terms comprehensively. Available from the JCT website for approximately £30–£40. Suitable for extensions, loft conversions, refurbishments, and similar projects. Both parties should read it before signing — it is written in plain English.
Simple Letter / Email Contract
For smaller jobs (under £5,000), a detailed email or letter from the builder confirming scope, price, timeline, and payment terms — countersigned by you — provides good protection. It is not as comprehensive as JCT but is far better than nothing. Many builders use their own quote documents for this purpose.
Consumer-Specific Contracts
The Consumer Rights Act 2015 implies certain terms into all consumer contracts — including that work must be done with reasonable care and skill, at a reasonable price if not agreed, and within a reasonable time. These protections exist regardless of whether you have a written contract — but a written contract makes enforcing them much easier.
Red Flags: When They Refuse a Contract
A builder who refuses to provide any written agreement is a significant red flag. Watch out for these specific warning signs:
- “We work on trust, we don't need paperwork” — this removes your legal protections
- Provides a quote but refuses to confirm it in writing — verbal-only quotes are unenforceable
- Wants a large upfront cash payment before any written agreement
- Evades questions about insurance or qualifications
- Pressures you to sign or pay immediately
For a complete list of warning signs, see: red flags when hiring a tradesperson in the UK. And if you need to compare quotes from multiple builders, read our guide on how to get multiple quotes for home work.
Contract Checklist: 10 Things Every Builder's Contract Should Cover
| Item | What It Should Cover |
|---|---|
| Scope of work | Detailed description of everything the builder will do — including materials, finishes, and what is excluded |
| Start and completion dates | Agreed dates, with provisions for what happens if they are missed |
| Payment schedule | Staged payments tied to progress milestones — never pay everything upfront |
| Variation clause | How changes to the scope will be agreed and priced — verbal changes are a major source of disputes |
| Materials specification | Brand, grade, and specification of key materials — prevents substitution with cheaper alternatives |
| Building Regulations | Who is responsible for obtaining approval and sign-off |
| Waste removal | Whether the builder removes waste or you arrange separately |
| Defects liability period | How long after completion the builder will return to fix defects at no charge (typically 6–12 months) |
| Dispute resolution | How disagreements will be handled — trade body mediation, adjudication, or court |
| Insurance | Confirmation the builder carries public liability insurance throughout the project |
For guidance on hiring a builder more broadly, including checking qualifications and reading reviews, see our full guide on how to hire a builder in the UK. If you are still in the dispute stage, read what to do if a tradesperson does a bad job.
Frequently Asked Questions
Is a verbal contract legally binding in the UK?+
Yes, verbal contracts are legally binding in the UK — but they are extremely difficult to enforce because there is no written record of what was agreed. If a dispute arises, it becomes your word against theirs. A written contract does not change the law — it just provides evidence of what was agreed, making enforcement practical rather than theoretical.
What is a JCT Minor Works contract?+
The JCT (Joint Contracts Tribunal) Minor Works Building Contract is a standard form contract designed for smaller building projects — typically under £250,000. It covers all the key terms in plain language and is widely used in the UK construction industry. It can be purchased from the JCT website for around £30–£40 and is appropriate for extensions, refurbishments, and similar residential projects.
What if a builder refuses to give me a written contract?+
This is a significant red flag. Any professional builder should be comfortable with a written agreement — it protects both parties. A refusal may indicate they plan to be vague about scope, change prices mid-project, or that they have something to hide. Do not proceed without something in writing, even if it is just a detailed email confirmation of the scope and price.
How should I structure payments for a building project?+
Never pay 100% upfront. A typical payment structure for a larger project might be: 10–20% deposit on contract signing, stage payments tied to completion of key milestones (e.g. foundations complete, structure complete, plastering complete), and a retention of 5–10% held back for 6–12 months after completion to cover any defects. For smaller jobs, payment in full on completion is reasonable.
What should I do if a builder wants to change the price mid-project?+
Legitimate variations happen — unforeseen conditions underground, changes you request, or specification upgrades you agree to. All of these should be agreed in writing before the additional work proceeds, with a clear price. Never accept verbal changes to price or scope. If your contract has a variation clause, follow it. If a builder is adding costs without written agreement, this is a warning sign.
Does a contract help if the builder does a bad job?+
Yes, significantly. A contract specifying the scope, materials, and standards makes it clear what 'good' looks like — and makes it easier to demonstrate in a dispute that the work fell short. Without a contract, disputes become arguments about what was actually agreed. See our full guide on what to do if a tradesperson does a bad job for the escalation process.
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