of British adults have hired a builder who turned out to be unreliable or unqualified. UK homeowners lost £14.3 billion to cowboy builders in the past five years.
That figure is not a fringe problem. More than one in three homeowners who has used a builder has had a bad experience. The difficulty is that the signs of a good builder and a bad one can look remarkably similar at the quotation stage — until they don't.
This guide covers the specific checks that matter, the questions to ask, and the signals that should make you pause before committing.
Check their business legitimately exists
Before anything else, verify that the business you're dealing with is real and traceable:
- Companies House — If they operate as a limited company, search at companieshouse.gov.uk. Check the incorporation date, registered address, and that their annual accounts are filed and up to date. A company registered last month that's quoting for a £60,000 extension warrants scrutiny.
- VAT registration — Any builder turning over more than £90,000 (the 2025 threshold) must be VAT registered. If they're quoting for significant work without mentioning VAT, ask why.
- Insurance — Ask for a copy of their public liability insurance certificate. At minimum, £1–2 million of public liability cover. If they can't provide one, do not proceed.
Cash-only requests are a serious red flag. A builder who insists on cash payment and can't provide business registration details is operating outside the tax system and outside any meaningful accountability. If something goes wrong, you have almost no recourse.
Check trade body membership
Membership of a recognised trade body isn't a guarantee of quality, but it is a meaningful signal. The most reputable:
- Federation of Master Builders (FMB) — Members are independently vetted and inspected. Verification at fmb.org.uk.
- National Federation of Builders (NFB) — Represents larger building contractors.
- TrustMark — Government-endorsed quality scheme. Verification at trustmark.org.uk.
These memberships require builders to meet standards and be independently assessed. They also provide dispute resolution if things go wrong — which matters more than people realise when they're choosing a builder, but matters enormously when they're dealing with one who has underdelivered.
Ask for references — and follow them up
References are only useful if you actually call them. Ask for two or three clients from the past 12–18 months whose projects were similar in size and scope to yours. When you speak to them, ask:
- Did the project finish on time, and if not, by how much did it overrun?
- Did the final cost match the original quote? If not, how were variations handled?
- Were they responsive and communicative throughout?
- Were there any defects after completion, and how did the builder respond to them?
- Would you use them again?
The last question is the one that matters most. Someone who has used a builder and been satisfied will say yes quickly and without qualification.
Never pay large sums upfront
The Federation of Master Builders advises that no more than 10–15% should be paid as a deposit before work begins. Stage payments should be tied to demonstrable progress milestones — foundation complete, roof on, first fix complete — not to arbitrary dates.
A builder who requires 30–50% upfront either has cash flow problems or is operating a model that leaves you with little leverage if the relationship deteriorates. Both are reasons for concern.
of homeowners who hired a rogue builder saw their renovation left unfinished. 33% reported low-quality work. These are not rare outcomes — they are predictable consequences of insufficient vetting.
Understand who will actually be doing the work
Many builders subcontract significant portions of their work. The person you meet, who impresses you with their knowledge and professionalism, may not be the person managing your site day to day. Ask directly:
- Who will be on site managing the project daily?
- Which trades do you employ directly, and which do you subcontract?
- How do you manage the quality and performance of your subcontractors?
There is nothing wrong with subcontracting — it's how most building projects work. But you should know who is responsible for what, and who you call if something isn't right.
Trust your instincts about communication
How a builder behaves during the quoting process tells you how they will behave on site. If they're slow to respond, vague about details, late to appointments, or dismissive of questions during the selection process — these behaviours will be magnified once the contract is signed and they have your deposit.
The builders who consistently deliver good outcomes are clear communicators. They answer questions directly. They raise problems early. They document changes in writing. None of this requires technical expertise to assess — it requires paying attention to how you're being treated before you've committed to anything.
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