The difference between a renovation you’d recommend to friends and one you tell horror stories about is almost always decided before work starts — when you choose the builder. Here are the ten checks we’d tell our own family to run on any London contractor, including us.
1. Check the company actually exists
Look the firm up on Companies House. You’re checking the company is registered, active, and has been trading under the same name — serial phoenixing (closing a company to escape liabilities, then reopening under a new name) is the classic red flag in building.
2. Ask for proof of insurance
Public liability insurance is non-negotiable; employer’s liability if they have staff. A professional firm sends certificates without hesitation.
3. Insist on a fixed price, itemised in writing
An “estimate” is a starting point for extras. A fixed-price quotation after a proper site survey means the builder has taken the risk of surprises — not you. The itemisation matters: it’s how you compare quotes fairly and how disputes get settled quickly.
4. Read reviews on platforms that verify them
Google reviews, Rated People, Checkatrade and MyBuilder verify that reviewers were real customers. A long trail of dated, specific reviews is worth far more than a glossy website.
5. Ask to see recent, real projects
Photographs taken by the builder on their own jobs — not stock images. Better still, before-and-after pairs. Any established firm can show you a portfolio of completed work.
6. Verify certifications for gas and electrics
Gas work must be done by a Gas Safe registered engineer; electrical work should be NICEIC (or equivalent) certified with certificates issued at completion. No certificates, no sign-off, no sale when you come to move.
7. Ask who actually does the work
Many “builders” are project managers subcontracting every trade. That’s not automatically bad, but it usually means slower jobs and diluted accountability. All-trades-in-house firms control quality and programme directly — one contact, one team, one point of responsibility.
8. Agree stage payments tied to milestones
Never pay a large deposit. Payments should track completed, visible work — strip-out done, first fix done, and so on. A builder who needs your money to start the job is telling you something.
9. Get a committed programme in writing
Start date, duration, and what happens if it slips. For landlords, every week of delay is lost rent — a builder who commits to a schedule in writing is pricing their own reliability.
10. Ask about aftercare and warranty
Snagging is normal; what matters is whether they come back. Ask what’s covered and for how long — for example, our bathroom installations carry a 2-year workmanship warranty.
The one-question shortcut
If you only ask one thing, ask: “Walk me through exactly what happens between me saying yes and you handing back the keys.” A good builder answers instantly, in detail, because they run the same process every week. Vague answers now become vague invoices later.
Vetting builders for a renovation? Here’s who we are, what we’ve built, and how to get a fixed-price quote — we’re happy to be checked against all ten.
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