Most renovation disasters are visible before the first invoice. The company is not registered, the insurance certificate has expired, the quote describes a different job from the one you asked for, or the deposit is large enough that the builder is working on your money rather than their own. None of that is obvious from a friendly first meeting, which is why a short verification routine is worth the effort.
This guide sets out what to check, in the order that makes sense: who you are dealing with, what protects you if something goes wrong, what the price actually covers, and how payments should be structured. It takes an evening, and it is the cheapest insurance you will buy for the project.
Start with the company, not the quote
Ask for the legal name of the business and its company number, then look it up on Companies House. You are looking for three things: that the company exists, that its filings are current, and that the people you met are connected to it. A company that has filed accounts late for several years is telling you something about how it is run.
Sole traders will not have a company record, which is not automatically a problem. In that case ask for identification and a trading address, and make sure the quote and contract name the same person or business that will receive your money. If a builder says they are VAT registered, the number can be checked with HMRC; if the invoice looks like a personal favour rather than a business transaction, slow down.
Two further questions are worth asking early. How long has the business traded, and will it subcontract any of the work? Subcontracting is normal, but you want to know who is responsible for the quality and the insurance of the people on site. If the answer is vague, ask for it in writing.
Check the insurance
Public liability insurance covers damage to your property and injury to visitors; employer's liability insurance is a legal requirement for anyone who employs staff. Both are relevant to a renovation, and both should be current.
- Ask for the certificate, not a promise that insurance exists.
- Check the policy dates and the level of cover.
- Call the insurer or broker named on the certificate and confirm the policy is active.
- Ask whether contract works or all-risks cover is in place for larger projects, and who arranges it.
A certificate that covers general building work may not cover specialist work such as roofing, groundwork or gas. If the job involves something outside the ordinary, confirm that the policy covers it before work starts. Keep copies of everything with your project file, alongside the scope and the payment schedule.
Confirm the trade registrations that apply to your job
Some work is regulated, and the person doing it needs to be registered for that specific task. Gas work must be done by a Gas Safe registered engineer, and you should check the card rather than assume. Electrical work in England and Wales is usually notified through a competent person scheme, or through building control, and you should ask who signs the certificate at the end.
Window and door replacements are commonly covered by a scheme such as FENSA, or by a building control application. Structural alterations, loft conversions and basement work will usually need building regulations approval, and possibly planning permission. A professional builder will raise these requirements before you ask, because they affect the sequence and the cost.
If a builder dismisses building control as paperwork that can be sorted out later, treat it as a serious warning. Approvals shape the work; they are not a formality that follows it.
Check references and look at real work
Ask for two or three recent projects of a similar size and type to yours. Then ask the questions that reveal how the business behaves when things get difficult, because every project has a difficult week.
- Was the final price close to the quote, and if not, why?
- Was the programme kept, and how were delays communicated?
- How were changes priced and approved?
- Was the site kept tidy and safe, especially with children or pets in the house?
- Would you use them again, and what would you do differently?
Look for reviews across more than one platform and read the middle of the range rather than the extremes. One bad review is often a customer mismatch; a pattern of complaints about the same thing, such as deposits or unfinished snags, is data. If a builder cannot name a single recent client who is willing to talk, that is an answer too.
Get the scope in writing before the price
Two quotes are only comparable when they describe the same work. Ask for a written scope that lists what is included, what is excluded, and what is an allowance to be chosen later. Preparation, waste removal, making good, protection, access equipment and building control fees are the items most often left out.
Where finishes are not yet chosen, ask for the allowance to be stated as a number and a specification level, so you can see what happens if you choose something better. Ask who supplies materials, who owns unused materials, and what happens if an order is delayed. Keep every revision of the scope with a version date, and make sure the final version is the one the contract refers to.
Use staged payments and never pay for nothing
Payments should follow completed stages rather than dates. A deposit that covers materials ordered for your job is normal; a large upfront payment for work that has not started is not. On bigger projects, ask for a payment schedule tied to milestones such as first fix, plaster and completion.
Keep a final balance or retention until snagging is finished and certificates, guarantees and manuals have been handed over. If you pay directly for materials, ask for receipts and check that the goods are on site or delivered to your address. Never pay into a personal account that does not match the contracting business, and never hand over cash without a receipt.
Know the warning signs
Some behaviours predict trouble regardless of how good the work looks in photographs.
- Pressure to decide immediately, or a price that is far below every other quote.
- No written quote, no insurance, no verifiable address and no references.
- A request for a large cash deposit before anything is ordered.
- Reluctance to put the scope, the programme or the payment stages in writing.
- Doorstep or cold-call offers for work you did not ask for.
A reputable builder can answer these questions without irritation because they have answered them many times before. If a simple request for documents feels like an argument, the working relationship will not improve once the walls are open.
Use a written agreement
The contract does not need to be intimidating. It needs to name the parties, the address, the agreed scope version, the price basis, the payment schedule, the start date and how changes are handled. It should say who is responsible for approvals, protection, waste and making good, and how disputes will be dealt with.
For larger projects, use a recognised contract or have a solicitor review the wording. Ask about warranties and who honours them if the business changes. At the end, collect the certificates and guarantees and keep them with the contract, so the next person who works on the house can see exactly what was done.
Frequently asked questions
Is a deposit normal for a UK renovation?
A deposit that covers materials ordered for your job is common, but a large upfront payment for work that has not started is not. Agree stage payments against completed work and keep a final balance until snagging and certificates are done.
How do I check a builder's insurance?
Ask for the public liability and employer's liability certificates, then confirm the cover is current and the work type is included by calling the insurer or broker named on the certificate.
Can I check a builder without a company number?
Some builders trade as sole traders, so there may be no Companies House record. In that case ask for references, insurance, and identification, and put the full agreement in writing before any payment.
The paperwork takes an evening, and it is the cheapest part of the project. It also changes the conversation: a builder who answers these questions clearly is usually the one who will still be answering the phone in month three.
This guide is general information for UK homeowners, not legal, financial or technical advice. Requirements differ across England, Scotland, Wales and Northern Ireland, so confirm project-specific rules with the relevant authority and qualified professionals.