How do I know if a builder is any good?

Almost every bad building story is a vetting story. The work itself is rarely the mystery — someone either has done this kind of job repeatedly and well, or has not — and the reason readers cannot tell is that they do not know which questions distinguish the two. The questions are not about whether the builder seems nice. They are about verifiable facts, and about evidence you can go and stand in front of.

Safety

What you'll need

• A written description of the job, before you speak to anybody
• Access to the public register of companies
• The relevant trade scheme registers for gas, electrical and glazing work
• Time to visit two or three previous jobs
• A note of every conversation, dated (optional)

Step by step

1. Write the job down before you contact anyone.Room by room, item by item: what is included, what standard of finish, who supplies what, what making good is expected. This document does three jobs — it makes quotes comparable, it reveals which builders read carefully, and it becomes the specification in the contract.
2. Build the list from recommendation, not from advertising.Someone who has had the same type of work done, in the same kind of property, and has lived with it for a year. Directory sites and scheme listings are a source of names, not a verdict — treat a listing as the start of your checking, not the end of it.
3. Prefer a trade that works locally and has done for years.Local reputation is a real constraint on behaviour, and a builder who intends to keep working in your area behaves differently from one who does not. Ask how long they have traded under that name in that area.
4. Verify the business is what it says it is.Get the full trading name, company number and a physical address, and look it up on the public register of companies. Look at how long it has traded, whether accounts are filed, and whether the same people have repeatedly dissolved and reincorporated companies — that pattern matters.
5. Verify competence on the scheme's own register.Gas Safe Register by number for any gas work — it covers Great Britain and Northern Ireland — with the card's appliance categories checked. The relevant electrical competent person scheme for notifiable electrical work, which in England and Wales means a Part P scheme and elsewhere the local equivalent. A glazing scheme for windows. Never from a logo, a certificate photograph or a claim on a website.
6. Ask which parts of the job they will subcontract.Most builders subcontract electrics, gas, plastering and roofing. That is normal. What matters is who those people are, whether they are registered, and whether the main contractor stands behind their work. Get the answer before you appoint.
7. Get the insurance certificate, not a description of it.Public liability at minimum, and employers' liability if they have employees. Ask for the certificate or for the broker's contact details. It takes them a minute, and a reluctance to provide it is itself informative.
8. Go and look at two finished jobs of the same type.Not photographs — addresses. Ideally jobs finished at least a year ago, because a job that has been through a winter shows movement, cracking, damp and finish failures that a job finished last month cannot. Ask the owner what went wrong and how it was handled.
9. Ask the previous clients the two questions that matter.Did the final price match the quote, and if not why. And: when something went wrong, what did they do about it? Every job has a problem; the answer tells you what happens on yours.
10. Notice how they respond to your specification.The strongest single signal is a builder who reads what you wrote and asks detailed questions about it — the drainage, the substrate, the make of the units, who is doing the making good. Vagueness at quoting stage becomes vagueness on site.
11. Confirm who is handling permissions and building control.Who applies, who pays, who calls the inspections, who receives the certificates. A builder who has not thought about this on a notifiable job has told you something important.
12. Only then compare prices, and only against the same specification.Price is the last filter, not the first. A cheaper quote from an unverified trade is not cheaper; it is a different, riskier product at a lower headline price.

Tips

• A good builder is usually busy. Immediate availability for a large job in peak season is worth asking a gentle question about.
• Ask to see a job in progress as well as a finished one. A tidy, organised, protected site is the single best predictor of finished quality that a layperson can read.
• Take notes with dates. Not because you expect a dispute, but because at quote stage three builders' verbal promises blur into one and you will not remember who said what.
• Trust your reaction to how questions are answered. "Don't worry about that" is a complete answer to nothing.

Common mistakes

• Treating a directory listing or review score as verification — Listings are paid for, reviews are gameable, and neither checks registration or insurance. They are a source of names; the checking is still yours to do.
• Accepting photographs instead of addresses — Photographs prove nothing about who did the work, when, or how it has aged. A visit to a year-old job is worth more than an entire portfolio.
• Choosing on price with no specification — Without a common specification, the quotes are pricing different jobs, and the cheapest is usually the one that has quietly excluded the most.
• Skipping the register check because they seem competent — Confidence and competence are unrelated, and the register check takes under a minute. For gas and electrical work this is the check that keeps people alive.

If it doesn't work

Questions people ask