How to Find a Reliable Builder in London

Checking reviews properly

Start with a Google Business Profile and, if the builder has one, a listing on a third-party review site. A high star rating on its own tells you very little; what matters more is volume, consistency and detail. A handful of five-star reviews posted within the same week, with generic phrasing like 'great job, highly recommend' and no specifics about the work done, is a weak signal and, occasionally, a sign of purchased or incentivised reviews.

Genuine reviews tend to mention specifics: the type of work, roughly how long it took, how communication was handled, and whether the final price matched the quote. It's also worth checking the reviewer's own history: a reviewer with a single review ever, posted for one builder, is weaker evidence than one with a normal spread of reviews across different businesses over time. A pattern of detailed, specific reviews building up steadily over months or years is the strongest signal available before you've met anyone in person.

Ask for evidence of similar completed work

A reliable builder should be able to show you photos, and ideally addresses or case studies, of work similar in scope to yours, not just their single best-ever project. If you're planning a loft conversion, ask specifically for loft conversion examples rather than accepting a general portfolio. Where possible, ask to see work that's a year or two old rather than freshly finished, since that tells you how the work has actually held up, not just how it looked on completion day.

Get a written, itemised quote, not a verbal estimate

A verbal 'about £15,000' is not a quote, it's a guess, and it gives you nothing to hold either side to if costs move. A proper quote should be written down, itemised by area of work or trade, and specific about what's included and what isn't: materials specification, waste removal, making good after each trade, and so on. Vague, single-line quotes are one of the most common sources of dispute later in a project, usually because both sides had a different idea of what was actually covered.

It's reasonable to ask a builder to clarify anything in a quote that isn't clear before you sign anything, and a reliable one will do this without pushback, because a clear quote protects them from scope disputes just as much as it protects you.

Insurance, and who's actually doing the work

Confirm public liability insurance before work starts, and ask to see the certificate rather than just taking a verbal assurance. This matters practically: if something goes wrong, damage to your property or a neighbour's, an injury on site, insurance is what stands behind the builder's ability to put it right. It's a reasonable, ordinary question to ask, and a legitimate builder will have the answer ready.

Also ask who will actually be on site: is it the company's own directly employed team, or subcontracted labour brought in for the job? Neither answer is automatically wrong, most construction projects involve some subcontracted trades, electricians and plumbers particularly, but you should know which parts of the job are being managed directly and which are being coordinated through a third party, since that affects accountability if something needs to be redone.

Understanding payment stages

A sensible payment structure is staged against progress: a modest deposit to secure the booking and materials, followed by payments tied to completed milestones, first fix, second fix, practical completion, rather than a single large payment upfront. Be wary of any builder asking for a large deposit, particularly anything over 25 to 30 percent of the total project value, before any work has started, since that shifts most of the financial risk onto you before you've seen any evidence of the work quality on your own project.

Companies House checks and red flags to watch for

If you're dealing with a limited company, a quick Companies House search is free and takes a minute: it confirms the company actually exists, how long it's been trading, and whether it has filed accounts recently. A company registered days before it quoted you, or one with lapsed filings, isn't automatically a scam, but it's a reason to ask more questions rather than fewer.

A short list of genuine red flags: a builder who cold-calls or knocks on your door offering to do work they've 'noticed' needs doing, particularly roofing, is a long-standing scam pattern in the UK and should be treated with real suspicion regardless of how plausible the pitch sounds. Insistence on cash payment only, pressure to sign a contract on the spot, and a quote that comes in dramatically below every other quote you've received are all worth treating as warning signs rather than good luck. A legitimate builder is rarely in a hurry to get you to commit before you've had time to think it over.

We're happy to be checked against this list

None of the above is intended as an argument for hiring Lian Construction specifically, it's the checklist we'd genuinely recommend using on any builder, including us. You can find our reviews, check our track record, and ask us the same questions about insurance, team structure and payment stages covered here before you commit to anything. Our construction company London page sets out how we scope and run projects, and if a builder isn't comfortable being vetted this way, that's useful information in itself.