Finding a good builder is the single most important decision on any renovation project. A reliable, competent contractor can deliver a kitchen extension on time and on budget; the wrong one can leave you with a half-built site, a depleted bank account, and months of legal battles.
The good news is that the vetting process, done properly, is not that difficult — it just takes time and a few straightforward steps that most homeowners skip.
Where to Find Builder Recommendations
Personal referrals are by far the most reliable starting point. Ask neighbours, friends, or colleagues who’ve recently had similar work done. If you admired someone’s extension or loft conversion, knock on the door and ask who built it. People are usually happy to share — both good and bad experiences.
Local trade bodies maintain vetted member lists:
- Federation of Master Builders (FMB) — members must pass an independent inspection and adhere to a code of practice. The FMB website has a “Find a Builder” search by postcode and trade.
- TrustMark — a government-endorsed quality scheme for home improvement trades. Registered firms have been assessed against technical and trading standards.
Architects and structural engineers often have strong local networks and can recommend builders they’ve worked with successfully. If you’re using a professional for design or oversight, asking for contractor recommendations is one of the most valuable things they can do for you.
Online platforms (Checkatrade, Rated People, MyBuilder, Houzz) provide another route — but check that reviews are verified, look for a spread of reviews over several years rather than a cluster of recent five-star ratings, and treat them as a lead source rather than a substitute for proper vetting.
How Many Builders to Approach?
Get at least three written quotes for any significant project. Two quotes give you a data point; three give you a reference range and something to reason from.
Don’t approach more than four or five — builders invest real time in producing detailed quotes, and flooding the market with requests signals that you’re not serious, which can deter the best contractors from bidding.
The Vetting Process: What to Check
References and Completed Work
Ask every builder for two or three references from comparable recent projects — similar type of work, similar value. Then actually call or visit them. Key questions:
- Did the work finish on time, or close to it?
- Were there significant unexpected cost increases, and how were they handled?
- Was communication good throughout?
- Would you use this builder again?
If possible, visit a completed job to see the quality of finish in person. Photographs are easier to stage than a real kitchen or bathroom.
Insurance and Registration
Every builder doing work in your home should carry:
- Public liability insurance — covers injury or damage to your property or third parties. Minimum £1 million, ideally £2–5 million.
- Employer’s liability insurance — required by law if they have employees.
Ask to see certificates directly — don’t just take their word for it. If they’re reluctant to provide them, walk away.
Check whether they’re registered for VAT (required above £90,000 annual turnover in 2026). If a builder quotes for a £60,000 extension and isn’t VAT-registered, that’s plausible. If the same builder is telling you they’re very busy with lots of large jobs, the VAT registration question becomes more pointed.
Companies House Check
Search for the builder’s limited company on Companies House (free at companieshouse.gov.uk). Look for:
- Date incorporated — how long have they been trading?
- Filed accounts — are they up to date? Overdue accounts can be a sign of financial difficulty.
- Any dissolved or struck-off companies associated with the director — particularly ones with similar trading names.
This takes five minutes and is one of the most revealing checks you can do.
Trade Body Membership
FMB membership requires an independent vetting process. Check that the membership is current at fmb.org.uk — memberships can lapse. TrustMark status can also be verified at trustmark.org.uk.
Comparing Quotes: What to Look For
A lower quote is not automatically better. Quotes often vary significantly because contractors have made different assumptions about the work. Before comparing figures, check:
Is the scope identical? If your specification is vague, each builder will have filled in the gaps differently. Compare what’s included and excluded in each quote.
Is labour and materials broken out? A fully itemised quote makes it far easier to assess value and to manage variations later.
What are the payment terms? Be wary of builders who ask for more than 10–15% upfront. A reasonable schedule ties payments to completed stages: foundations poured, structure up, roof on, plastered, and so on. Never pay in full or near-full before completion.
What’s the programme? Ask for a written start date and estimated completion date. Ask what happens if they’re delayed.
Typical Costs as a Sanity Check (2026, England)
| Project Type | Typical Cost Range |
|---|---|
| Single-storey rear extension (20–25 m²) | £45,000 – £75,000 |
| Loft conversion (dormer) | £55,000 – £90,000 |
| Full kitchen refit (supply and fit) | £15,000 – £35,000 |
| Bathroom renovation | £8,000 – £20,000 |
| Full house rewire (3-bed semi) | £5,000 – £9,000 |
If a quote comes in 30–40% below market rate, ask why. It may mean the builder hasn’t included something, is desperate for work, or intends to use substandard materials.
Red Flags to Watch Out For
Pressure to decide quickly. “I can only hold this price until Friday” is a sales tactic. A builder who does good work doesn’t need to pressure you.
Cash-only or off-the-books work. This makes VAT reclaim impossible if you’re eligible, leaves you with no paper trail, and often signals that the builder isn’t properly registered or insured.
Reluctance to put things in writing. If a builder is uncomfortable with a written contract, that’s a serious warning sign. Everything should be documented — the scope, the price, the programme, and the payment schedule.
No fixed address or very recent company formation. Not automatically disqualifying, but worth scrutinising more carefully.
Vague answers about subcontracting. Most builders subcontract some elements (plumbing, electrics, plastering). That’s normal. What you want to know is who manages those subcontractors and who is responsible to you for their work.
Contracts and Protection
Once you’ve selected a builder, use a written contract. The JCT Minor Works Building Contract is the standard form for residential projects under approximately £250,000 and is available from the JCT directly or from RIBA for around £40. It sets out both parties’ rights, payment terms, dispute resolution, and termination rights.
At minimum, your written contract should cover: scope of works, contract sum, payment schedule, programme, variation procedure, defects liability period, and what happens if either party wants to terminate.
A handshake deal might feel friendlier, but it leaves you with almost no protection if things go wrong.
