The single most consequential decision on any building project is who you hire. A good builder makes almost everything easier. A bad one makes almost everything terrible. The difference between the two is often not visible from a website, a brochure, or the first meeting. You have to dig.
Most homeowners don't dig. They get three quotes, pick the middle one, and proceed. That approach puts the quality of the outcome largely down to luck. This guide sets out how to reduce the luck component substantially.
Where to Start Looking
Personal recommendation remains the most reliable starting point. If someone you trust has used a builder recently, for a similar type of project, and was happy with the result, that's meaningful information. Notice "recently" and "similar type": a builder who was great at a kitchen refit in 2019 may not be right for a structural extension today, and standards vary.
Trade body directories are useful as a filtering tool, not as a guarantee. Federation of Master Builders (FMB), TrustMark, and Checkatrade-verified builders have at minimum passed a vetting process. NICEIC for electrical work, Gas Safe for gas, FENSA for windows: these are competence registers with defined minimum standards. Being listed on these registers tells you something meaningful. Not being listed on them is a red flag for trades that require it.
Platforms like Rated People, MyBuilder and Checkatrade aggregate reviews but vary in how rigorously reviews are verified. Use them to generate leads and identify options, not to substitute for your own vetting process.
Your architect or structural engineer often knows good local builders. Their recommendation carries weight because they work with contractors repeatedly and understand the difference between those who deliver well and those who don't.
Initial Contact and Shortlisting
Start with more candidates than you need. For a significant project, approach six to eight builders. Expect some not to respond, some to decline the project (too small, wrong type, too far away), and some to respond but prove unsatisfactory at interview stage. From an initial list of eight, getting three to submit proper quotes is a reasonable outcome.
In your initial contact, describe the project briefly: the type of work, approximate scale, your intended timeline, and your location. Ask whether they're interested in quoting and, if so, whether they have capacity in the relevant period. A builder who is already booked out for the next year isn't wrong for your project, but they're wrong for your timeline.
Phone calls tell you more than emails at this stage. How does the person speak about your project? Do they ask intelligent questions or just say yes to everything? Are they articulate about their approach? Do they listen?
The Site Visit
Invite shortlisted builders to visit the site before quoting. This is standard practice for any significant project and any good builder will expect it. The visit tells you a lot about the person:
Do they turn up on time? Do they come prepared, with a notepad or measuring tape? Do they look at the things that matter (access, ground conditions, existing structure, party walls) or just the finished room layout? Do they ask about what you want to achieve, not just what you want to build?
Use the site visit as an interview as much as a briefing. Ask about their experience with similar projects. Ask how they manage subcontractors. Ask how they communicate with clients during a build. Ask what typically causes projects like yours to go over budget or programme, and what they do about it.
Ask every builder the same questions in the same order. Comparing answers is much easier if you've consistently asked the same things. Write the questions down beforehand and take notes during the conversation. You will forget the detail within 48 hours if you don't.
Vetting Checks
Before appointing anyone, make these checks. They take time. Do them anyway.
Companies House. If the builder operates through a limited company, check the company on Companies House (free to search). When was it incorporated? What are the filed accounts? Has it been struck off and re-formed (a common pattern with contractors who want to escape debts)? Are there multiple dissolved companies with the same director? None of these is automatically disqualifying, but they're information you should have.
Trade body membership. Don't just take their word for it. Check the relevant trade body directory directly: FMB members are searchable on fmb.org.uk, TrustMark businesses on trustmark.org.uk. Gas Safe numbers can be verified on the Gas Safe Register. An NICEIC registration number can be checked on niceic.com.
Insurance. Ask for proof of public liability insurance. Minimum £2m public liability for a residential project is standard; £5m is better for significant projects. If they cannot produce a current insurance certificate, they're uninsured. Don't proceed.
References. Ask for two or three references from recent, comparable projects and follow them up by phone. Email responses to reference requests are less informative than a real conversation. Ask the reference: did the work finish on budget? On time? How did the builder communicate? What would they do differently? Would they use the same builder again?
Visit a current or recent site. Ask whether you can visit a project they're currently working on or have recently completed. You're looking at the quality of work, but also at the way the site is run: is it tidy and organised? Are materials stored properly? Is there evidence of care and attention?
Trust Your Instincts, but Understand Them
Instinct matters. If something about a contractor makes you uncomfortable, that feeling is worth examining. A builder who talks over you, dismisses your concerns, is vague about specifics, or makes you feel that you're being managed rather than served is telling you something important about how they'll behave once they have your deposit and a start date.
But instinct can mislead. Articulate and confident isn't the same as competent and honest. Someone who charms you in a meeting may do excellent work; someone who's quieter and less polished may be an outstanding builder. Use instinct as one input alongside evidence, not instead of it.
Finding a Builder at the Right Time
Good builders are busy. In most parts of the country, a builder with a strong reputation has a waiting list of three to six months, sometimes more. The implication: start looking for a builder earlier than you think you need to.
Don't wait until you have planning permission and building regulations approval and you want to start next month. Start identifying and talking to builders at planning application stage. You'll have a much better sense of who you want to appoint by the time approvals come through, and you can get yourself into their diary rather than taking whoever is available immediately.
Builders who are immediately available when you want them are not always the ones you want. Occasionally a quality contractor has a cancellation. More often, instant availability means no one else wants them at that price.