Questions to Ask a Contractor Before You Hire: A UK Vetting Guide

What predicts how a job will go is almost never the price. It sits in the answers to a dozen awkward questions most homeowners never ask, because asking a stranger for proof of insurance in your own kitchen feels rude. It isn't — anyone running a proper business has been asked before and keeps the paperwork on their phone.

Below is the script, in order.

There is no general licence to be a builder in the UK. Anyone can print a van livery on Monday and quote your extension on Tuesday. Registration exists only for specific trades — gas, notifiable electrics, replacement windows — so for everything else you rely on evidence, references and a contract, as covered in our guide on how to hire a contractor.

You are testing three things: recent experience of this exact job, a system for the parts that go wrong, and a business that will outlive the guarantee.

• •Do it yourself: filling and repainting, a tap washer or flush valve, a like-for-like light fitting, click-fit flooring.
• •Always hire: anything on the gas supply (legally Gas Safe registered only), new circuits or a consumer unit change, notching structural timber, chimney breasts, party walls.

Five minutes on the phone saves three wasted site visits. Listen for hesitation rather than for the answer you want.

• •"How many of exactly this job have you done in the last twelve months, and can I see two?" A real answer contains a number and an offer.
• •"Are you doing the work or subcontracting it, and who is my point of contact?" Subcontracting is normal; not mentioning it isn't. You want a named person and a mobile number.
• •"What else is running while my job is on?" Usually "two others" — better known now than when your kitchen sits half-finished.

These carry legal weight and get skipped because they feel confrontational. Ask at the site visit, photograph the documents, verify independently. Unregistered notifiable work surfaces years later, when a buyer's solicitor asks for the completion certificate. Check what consent your job needs in our guide to planning permission and building regs.

• •"What is your Gas Safe registration number?" Check the register, and read the categories on the back of the card — boilers and cookers are separate qualifications.
• •"Are you on a Part P competent person scheme?" NICEIC, NAPIT and ELECSA members self-certify notifiable electrics. If not, you need a building notice at roughly £200–£400.
• •"Can I see your public liability certificate?" £2m is the working minimum, £5m for structural work. Check the dates and that the insured name matches the invoicing name.
• •"Who notifies building control and receives the completion certificate?" Scotland uses a building warrant, Northern Ireland its own regulations, listed buildings extra consents. Your council is the only authority on its own rules.
• •"Are you a registered waste carrier, and what if we find asbestos?" Duty of care follows the rubble — fly-tipped, you get fined. Anything pre-2000 may contain asbestos; the answer you want is "we stop and sample it".

Most disputes are not about workmanship, they are about a number that moved. Pin the terms down in writing, then compare estimates line by line rather than by the total at the bottom.

One question outperforms the rest: "what are the three most likely things that would push this above your figure?" A good builder answers instantly — rotten joist ends, an out-of-level floor, a soil pipe in the wrong place. "Nothing, it's fixed" means they haven't looked.

• •"Quote or estimate?" A quote is a fixed offer you can hold them to; an estimate is an informed guess and can legitimately move.
• •"Is VAT included, and are you registered?" A £9,000 job arriving as £10,800 is the commonest shock. Registration bites above £90,000 turnover, so a small outfit may genuinely not charge it.
• •"What triggers each payment?" A materials deposit of 10–25% is normal; half up front is not. Pay by credit card — Section 75 covers £100 to £30,000.
• •"Will you accept 5% retention for three months?" Standard above roughly £10,000, and the fastest way to get snags fixed.
• •"Your day rate outside the quote?" In 2026, about £200–£300 for a builder, £180–£280 for a plumber or electrician, plus 30–40% inside the M25.

These sound minor and cause most of the friction, so agree them at quote stage and put them in writing. A contract signed in your home usually carries a 14-day cancellation right under the Consumer Contracts Regulations 2013, and our renovation contract checklist covers the clauses worth insisting on.

• •Working hours, weekend working, key access, and where the skip goes — on the highway it needs a council permit, £30–£60 a week on top of £220–£350 hire.
• •"How long do I have to raise snags, and how fast do you return?" Two weeks to list, two weeks to fix.
• •"What guarantee, and is it insurance-backed?" Twelve to 24 months on workmanship is typical; an insurance-backed guarantee costs 1–2% of contract value and survives the company folding.

Tenants are usually asking the wrong person. Under section 11 of the Landlord and Tenant Act 1985, structure and exterior, heating, hot water and sanitary fittings are the landlord's responsibility, and you should not be commissioning a builder for any of it. Report faults in writing with dated photographs; if nothing happens, council environmental health can inspect. Paying for repairs and deducting it from rent is procedurally strict — take advice first.

What you can safely arrange is anything that leaves the property as you found it: cleaning, gardening, curtains on existing fixings, freestanding shelving, peel-away wallpaper. More in our guide to decorating a rented home without losing the deposit.

• •Get written consent — an email reply is enough — before anyone drills into a wall, tile or worktop. Verbal permission from an agent evaporates at check-out.
• •Photograph before and after. Deposit adjudicators decide on evidence, and the burden of proving a deduction sits with the landlord.
• •Never instruct anyone to isolate gas, alter the consumer unit or touch the boiler. That is the landlord's contractor, behind the landlord's annual gas safety record.

Three quotes is the right number — one gives no context, five wastes everyone's time. If one sits 30% below the rest, the gap is nearly always something missing from the specification, so find it before you celebrate. Working out the budget first shortens the whole conversation, which is the point of our guide on budgeting a home renovation.

• •"Do I need a written contract for a £1,500 job?" Yes. An email confirming scope, price, VAT, dates and payment stages is a contract.
• •"Is a deposit a red flag?" No — materials cost money. A deposit bigger than the materials bill, demanded in cash, is.
• •"What if it goes wrong?" Complain in writing with a deadline, use the trade body's dispute service, then ADR. Small claims covers £10,000 in England and Wales; Scotland's simple procedure £5,000.