I stood in a kitchen in Giffnock a while back while a woman went through a folder looking for the paperwork on windows fitted eight years earlier. She found it. Twenty year guarantee, printed nicely, signed. The company on the letterhead had stopped trading five years before that, and the phone number rang out to nothing.
That folder was worth exactly what the company behind it was worth, which by then was nothing at all. It’s a common enough story, and the word “guarantee” is doing a lot of work in double glazing sales, because it covers three completely different arrangements.
Three different promises wearing the same word
The manufacturer’s guarantee on the sealed unit. This comes from whoever made the glass unit, not from whoever fitted it. It typically covers the unit failing, which in practice means the perimeter seal breaking down and the cavity misting up. It’s a product warranty on a manufactured item, and it usually covers supply of a replacement unit rather than the labour of anyone coming out and fitting it.
The installer’s guarantee on the workmanship. This is the fitting firm promising their own work. Sealed properly, fitted square, hardware adjusted, no leaks. It’s the promise that covers most of what actually goes wrong in the first few years, and it is only as good as the company standing behind it. If they close, it closes with them. There is nobody else to ring.
An insurance backed guarantee. This is a separate insurance policy, bought from an underwriter, that pays out to honour the installer’s obligations if the installer is no longer trading. It’s the only one of the three that survives the company going under, which is precisely the situation you needed a guarantee for in the first place.
Most people who think they have a twenty year guarantee have the second sort.
Why an installer only guarantee is thinner than it looks
The double glazing trade has an unusually high turnover of companies. Firms close and reappear under a new name with the same people, the same van and the same phone number. Sometimes that’s straightforward business failure. Sometimes it’s a deliberate way of shedding a book of guarantee obligations and starting clean.
Either way, the effect on you is the same. The longer the guarantee, the more it depends on the company outliving it, and a twenty year promise from a business that has existed for eighteen months is a statement about ambition rather than about your windows.
A modest guarantee from somebody who has been in the same town for decades tends to be worth more in practice than a long one from a name nobody has heard of, because the thing that makes a guarantee real is somebody still being there to answer the phone.
The questions worth asking before you sign
Is it insurance backed, and who is the underwriter? Ask for the name of the insurer and the policy document, not just the installer’s word for it. An insurance backed guarantee is a real financial product with a real provider behind it. If they can’t tell you who that is, it isn’t one.
Is it transferable if I sell the house? Some are, some aren’t, some transfer once and only if you notify somebody within a set period. A guarantee that transfers is a small selling point. One that doesn’t is a surprise for the next owner.
What’s actually excluded? This is where most of the value evaporates. Misting of the sealed unit is very often covered. Hardware is very often not. Neither are gaskets and weather seals, and neither is adjustment.
That’s back to front from how windows actually fail. Handles, hinges, friction stays, locking gearboxes and rubber seals are the parts that wear out and need attention, and they’re routinely written out of the guarantee as consumables or wear and tear. The sealed unit, the part most likely to be covered, is also the part most likely to last.
Does it require annual servicing to stay valid? Some guarantees carry a condition that the windows are serviced yearly, by the installer, at your cost, and that failing to do it voids the cover. Look for that clause specifically. A guarantee you have to keep buying is a maintenance contract with a nicer name on it.
Is any of it in writing? A verbal guarantee is a conversation.
If you’ve got a blown unit and you think you’re still covered
Chase the original installer first. Before you ring anybody else, including us.
It costs nothing to try. Dig out the paperwork, find the date of installation and the name of the company, and phone them. If they’re still trading and the unit is inside its term, that’s a job that should cost you nothing or close to it, and there’s no sense in paying us for something somebody else already owes you.
If the number’s dead, check whether the guarantee was insurance backed, because there may be a policy to claim against even though the company has gone. The paperwork will name the provider if there is one.
And if you send us a photo and tell us who fitted the windows and roughly when, we’ll say straight out if it looks like you’re still covered and ought to be chasing them instead of paying us. We’d rather tell you that than take the money. We’d sooner be the firm you ring in five years than the one that quietly took a job you shouldn’t have paid for.
Two quick ones people ask
Does replacing a sealed unit void the guarantee on the rest of the window?
Usually not, but it depends on the wording. Some installer guarantees do have a clause about work carried out by others. If your windows are still within an active guarantee period, that’s the strongest reason of all to go back to the original company first.
The firm that fitted my windows has reappeared under a similar name. Is it the same company?
Possibly, and it may make no difference. A guarantee is an obligation of the specific company that issued it, and a new company with a similar name is generally not bound by the old one’s promises. Worth asking directly rather than assuming.
Where to start
Find the paperwork. Read the exclusions rather than the headline number. Ring whoever fitted them if there’s any chance the cover is live.
If it turns out there’s nothing to claim, that’s when to talk to us. WhatsApp a photo of the affected pane and we’ll give you a rough figure, or ring 01698 604 278 between eight and five on a weekday.
If the guarantee has run out and the unit has gone, replacing just the glass is far cheaper than most people expect, and our sealed unit replacement page explains how it works.
Related advice
If you would rather just ask, get in touch.
You will find around fifty more guides like this one in our advice section.
Written by the team at Wishaw Window Repairs. Over thirty years repairing uPVC windows and doors across Lanarkshire.