How to vet a window installer

Anyone can print a smart brochure. Vetting is how you tell a company that will fit your windows cleanly and stand behind the work from one that will take your deposit and disappear. Here is what to check, and why each check matters.

Confirm the business is real and established

Start with the basics. Is there a registered company number, a trading address and a landline rather than just a mobile? How long has the firm been trading under its current name? A company with a genuine history in your area is easier to visit, easier to check and far more likely to be around when you need to call on a ten-year guarantee. Be wary of businesses that have recently dissolved and reappeared under a new name, which can be a way of shedding old guarantee obligations.

Check accreditation is current, not just claimed

Registration with FENSA or CERTASS means an installer can self-certify that its work meets building regulations, so you avoid arranging a separate building-control inspection. TrustMark adds a layer of government-endorsed vetting. The important word is current: badges on a website can be out of date, so verify the registration directly on the relevant scheme's own checker before you rely on it. An installer who is genuinely accredited will be happy for you to confirm it.

Insurance, guarantees and deposit protection

Ask what happens to your money and your workmanship cover if the worst happens. A meaningful installer will carry public liability insurance and offer an insurance-backed guarantee, which protects the warranty on your windows even if the company later ceases trading. Deposit protection matters too, so ask how any upfront payment is safeguarded. If a company cannot explain these points clearly, treat that as a warning in itself. Building a solid list of candidates first makes this easier — a structured approach to finding vetted UK window companies means you start from a stronger position.

Look at workmanship and aftercare

Ask to see recent local jobs, and if you can, speak to the homeowners. Were the fitters tidy, punctual and respectful of the property? Was the site left clean? Crucially, what happens after the work is signed off — if a handle loosens or a seal fails a year later, who comes back and how quickly? Good aftercare is one of the clearest signals of a company that values its reputation over a quick sale.

Get the important things in writing

Before any money changes hands, the quote and contract should spell out the frame material and colour, the glass specification, the number of opening lights, trims and cills, disposal of the old units, the guarantee terms and the payment schedule. If funding or a payment plan is discussed, remember that any contribution options are subject to eligibility and a home survey — it is worth understanding the ways to spread the cost of new windows so you can ask the right questions rather than being sold a plan on the doorstep.