Badly fitted windows: signs, your rights and what to do

How to tell if your windows are badly fitted

Badly fitted windows show up in how each window opens, seals and sits in the wall, so check every one before the final payment. Work through six checks:

• Open, close and lock every window and glazed door.
• Look for daylight, open gaps or thick sealant where the frame meets the wall.
• Feel for draughts around each frame on a windy day.
• Watch for water coming in around the frames during rain.
• Check that each frame sits level and square in the opening.
• Inspect the plaster, reveals and sills for damage or unfinished making good.

Take dated photos of each fault. Which? says the more you have in writing the better, and that you need a record of the problems, including photographs, if you claim against the company in court.

Problems after fitting are the most common kind in Which?'s survey: 13% of the 3,409 double glazing owners Which? asked had one, against 8% who had a problem with the installation itself.

Fitting fault or faulty glass?

Misting between the panes is a question about the sealed glass unit, so check the glass line of your double glazing guarantee as well as the fitting. The sister site's guide explains misting between the panes.

Can windows be installed incorrectly?

Yes, and the law treats incorrect fitting as the installer's breach. Section 15 of the Consumer Rights Act 2015 says goods installed incorrectly by the trader, or under the trader's responsibility, do not conform to the contract. Section 49 adds that every service contract includes a term to perform the service with reasonable care and skill.

The installer that sold you the windows stays responsible when a subcontractor did the fitting. Which? says the company "is responsible for its subcontractors' actions and standards of work", and Citizens Advice tells you to take the problem up "with whoever arranged the installation".

Your rights when windows are badly fitted

You can require the installer to repair or replace badly fitted windows. The installer must do it within a reasonable time, without significant inconvenience to you, and pay every cost of labour and materials (section 23). Your remedies run in this order:

1. Repair or replacement of the windows (section 23), or repeat performance of the fitting (section 55).
2. A price reduction or the final right to reject the windows when repair or replacement fails or cannot be done (section 24).
3. A price reduction for the fitting when repeat performance is impossible or late (section 56).

The installer can refuse the remedy you chose only when it is impossible, or disproportionate compared with the other remedy (section 23(3)).

The six-month rule and time limits

A fault that appears within six months of delivery is taken to have been there on delivery, unless the installer shows otherwise (section 19(14) and (15)). After that, a contract claim must start within six years in England and Wales (Limitation Act 1980, section 5) and five years in Scotland (Prescription and Limitation (Scotland) Act 1973, section 6).

Is it a Building Regulations fault?

A badly fitted window can also break Building Regulations, which have applied to all replacement glazing since 1 April 2002. The Planning Portal lists the areas they cover: thermal performance, safety, air supply, means of escape and ventilation. A replacement window is a "controlled fitting".

Safety glazing is required in critical areas, which the Planning Portal lists as:

• any glazed panel up to 800mm from floor level
• any glazed door up to 1500mm from floor level
• any side panel within 300mm of a door, up to 1500mm from floor level

Building Regulations faults go to whoever certified the work. FENSA acts only on Building Regulations compliance, for a FENSA Approved Installer still trading, on work completed less than six years ago in a home in England or Wales.

CERTASS limits its complaints to Building Regulations and industry codes of practice, and gives the installer the chance to return and put the work right. Work by an unregistered installer needs approval from building control instead.

A registered installer gives you a certificate and notifies the council within 30 days of completion (Building Regulations 2010, regulation 20). Check the installer's registration with our guide to double glazing installers.

What to write to the installer

Write to the installer that sold you the windows, list each fault, attach the photos and say what you want done by a set date. Citizens Advice suggests this wording:

"The Consumer Rights Act 2015 says that goods must be correctly installed, if installing them was part of the contract. In my opinion, you did not install them correctly when you carried out this work."

Then say what you want: the fault fixed, or a refund.

Which? sets out three steps from the first letter:

1. Contact the company as soon as you find the problem, and follow any phone call with a letter or email.
2. Agree a final date for the work if the company misses its own date.
3. Give a final ultimatum: fix it within a short deadline, or you will have someone else do it and claim back the cost.

Which? also advises against dealing with the issue over text or WhatsApp.

Before you pay the balance

Check every window before you pay the final balance, because stage payments mean "problems can be put right before you make the final payment", as Citizens Advice puts it. Agree the payment stages in the contract before work starts, and ask for the Building Regulations certificate once the job is done. Our guide to the double glazing deposit sets out a staged payment schedule.

Get an independent inspection

An independent inspection gives you expert evidence when the installer disputes a fitting fault. DGCOS mediators may arrange an inspection for customers of DGCOS members, and "this service is also free to you". Outside a scheme, Citizens Advice notes that you will probably have to pay for an expert opinion.

Ask the inspector to assess the fitting against BS 8213-4:2016, the British Standard code of practice for the survey and installation of windows and external doorsets.

If the installer will not put it right

Get written quotes from other installers for putting the work right, then take the dispute further. Which? advises getting quotes from other glazing installers for fixing the problem, so you can show the company how much you will claim back.

The next steps are the installer's dispute resolution scheme, the Citizens Advice consumer service and a court claim, set out in our guide on how to complain about a double glazing company.

Questions people ask