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 are vetted and have their work inspected.1 The FMB website has a “Find a Builder” search.1
  • TrustMark, a government-endorsed quality scheme for home improvement trades.2 Registered businesses have been vetted to meet required standards and have committed to good customer service.2

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.3 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. It is generally voluntary rather than required by law, so ask to see the policy.4 Policies commonly provide cover of £1 million or more, with higher limits on larger jobs.
  • Employer’s liability insurance, required by law if they have employees.5

Ask to see certificates directly, don’t just take their word for it.3 If they’re reluctant to provide them, walk away.

Check whether they’re registered for VAT (registration is required once taxable turnover over the last 12 months goes above £90,000).6 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 (the basic company search on GOV.UK is free).7 Look for:

  • Date incorporated, how long have they been trading?7
  • 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 members are vetted and their work inspected.1 Check that the membership is current at fmb.org.uk, as memberships can lapse.3 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 a large payment upfront: a deposit of around 10% is often used as a guide, though the right amount depends on the project.3 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 TypeTypical 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 far below comparable quotes, ask why.3 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.3

Cash-only or off-the-books work. It leaves you with no proper invoice or paper trail, and often signals that the builder isn’t properly registered or insured.3

Reluctance to put things in writing. If a builder is uncomfortable with a written contract, that’s a serious warning sign.3 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 publishes Home Owner contracts written specifically for people appointing contractors or consultants to work on their home.8 For larger jobs designed by an architect, the JCT Minor Works Building Contract is intended for smaller, basic projects where the work is simple in character.9 Both set out the parties’ obligations, 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.

References (9)

Figures in this note were checked against the sources below on 2 October 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.

  1. 1technicalgoodFederation of Master Builders, guidance.RN-81QXS4The FMB's own home page, which states that its member builders are vetted and have their work inspected before homeowners are pointed to them.
  2. 2technicalstrongTrustMark.RN-ZGS3SNTrustMark is the government endorsed quality scheme for work in and around the home, endorsed by the Department for Energy Security and Net Zero and the Department for Business and Trade. It vets registered businesses against required standards and holds ISO 9001, ISO 27001 and Cyber Essentials accreditation. Registration is the marker to check for grant-funded energy efficiency work, so a note about a subsidised loft insulation installer should point readers here rather than to a lead generation directory.
  3. 3technicalgoodFederation of Master Builders, guidance.RN-8ZTC0XThe Federation of Master Builders' homeowner guide to choosing and paying a builder. It says a small deposit is common on larger projects where materials or made-to-order items are bought in advance, with around 10% as a guide.
  4. 4technicalvery strongHealth and Safety Executive, a government page.RN-WGN915HSE's plain-language guide to the insurance a builder with employees must legally hold, and the clearest statement of the difference homeowners get wrong. Employers' liability insurance is compulsory and covers claims by the contractor's own employees; public liability insurance is different, covering claims by members of the public or other businesses, and is generally voluntary. The minimum cover is £5 million per occurrence including costs, though the guide notes most insurers offer at least £10 million and that a group of companies must carry £5 million between them. The insurer must be authorised under the Financial Services and Markets Act 2000. A certificate of insurance must be displayed where employees can easily read it, and since 1 October 2008 it may be displayed electronically provided employees know where to find it. Penalties: up to £2,500 for each day without suitable insurance, and up to £1,000 for failing to display the certificate or refusing to show it to an HSE inspector.
  5. 5technicalvery strongHealth and Safety Executive, guidance.RN-H2UIG9HSE's summary page for leaflet HSE40, which confirms that employers' liability insurance is compulsory for businesses with employees.
  6. 6technicalvery strongHM Revenue and Customs (GOV.UK), a government page.RN-J2B1F3When a business must register for VAT: the taxable turnover threshold, the backward and forward look tests, and voluntary registration. This is why a small builder's quote may carry no VAT at all while a larger firm's carries 20% on the same work, which is a genuine price difference and not a discount.
  7. 7technicalvery strongCompanies House (GOV.UK), guidance.RN-KBZ7STThe GOV.UK entry point to the Companies House search, confirming that company details, officers and filings can be viewed free of charge.
  8. 8technicalfairThe Joint Contracts Tribunal, guidance.RN-R4944ZThe Joint Contracts Tribunal's page for its Home Owner contracts, which it describes as written for homeowners appointing contractors or consultants for building work.
  9. 9technicalfairThe Joint Contracts Tribunal, guidance.RN-L0783SThe Joint Contracts Tribunal's description of the Minor Works Building Contract: for smaller, simple projects where the employer supplies the design, usually through an architect.

  1. Federation of Master Builders, Federation of Master Builders, accessed 30 September 2026. fmb.org.uk

  2. TrustMark, TrustMark, accessed 30 September 2026. trustmark.org.uk

  3. How to choose a trusted builder in the UK, Federation of Master Builders, accessed 2 October 2026. fmb.org.uk

  4. Employers’ Liability (Compulsory Insurance) Act 1969: A brief guide for employers (HSE40), Health and Safety Executive, accessed 30 September 2026. hse.gov.uk

  5. Employers’ Liability (Compulsory Insurance) Act 1969: A brief guide for employers, Health and Safety Executive, accessed 30 September 2026. hse.gov.uk

  6. Register for VAT: When to register, HM Revenue & Customs (GOV.UK), accessed 30 September 2026. gov.uk

  7. Get information about a company, Companies House (GOV.UK), accessed 30 September 2026. gov.uk

  8. JCT Home Owner Contracts, The Joint Contracts Tribunal, accessed 30 September 2026. corporate.jctltd.co.uk

  9. JCT Minor Works Building Contract, The Joint Contracts Tribunal, accessed 30 September 2026. corporate.jctltd.co.uk