The typical guarantee for new windows and doors in the UK is 10 years, though premium installations can offer up to 20 years on the sealed units and framework. The most common industry standard is a 10-year insurance-backed guarantee, which is required for FENSA or CERTASS registration compliance (GOV.UK, 2026).
The guarantee length depends heavily on the product type, installation company and whether you choose a trade body registered installer. A 10-year guarantee is standard for uPVC windows and doors, while timber or aluminium frames may offer 20-year guarantees on the profile but only 5–10 years on the glazing units. The guarantee typically covers manufacturing defects, sealed unit failure (condensation between panes) and hardware malfunction, but excludes damage from misuse, accidental breakage or lack of maintenance.
Standard 10-year guarantee covers sealed unit failure
Most UK window and door installers provide a 10-year guarantee on sealed double or triple glazing units. The Energy Saving Trust notes that if condensation appears between the panes within this period, the unit should be replaced free of charge (Energy Saving Trust, 2026). This guarantee is often insurance-backed, meaning you are covered even if the installer goes out of business. Always check the small print, some guarantees exclude labour costs after the first year, leaving you to pay for fitting the replacement unit.
FENSA and CERTASS guarantee minimums
Installers registered with FENSA or CERTASS must offer a minimum 10-year guarantee on their work, as required by the Competent Person Scheme (GOV.UK, 2026). This guarantee covers the installation itself, not just the product. It protects you if the windows or doors are poorly fitted and cause draughts, leaks or structural issues. Without a registered installer, you may have no guarantee at all, and building regulations compliance is your responsibility.
Timber and aluminium guarantees differ from uPVC
Timber windows often come with a 20-year guarantee on the timber frame against rot, but only a 5-year guarantee on the glazing and paint finish. Aluminium windows typically offer a 20-year guarantee on the powder coating and a 10-year guarantee on the sealed units. The British Research Establishment (BRE) advises that guarantees for timber products are conditional on annual maintenance, such as repainting or re-varnishing (BRE, 2026). uPVC windows generally have a 10-year guarantee with no maintenance requirements beyond cleaning.
A worked example
A typical 1930s semi-detached house in Manchester replacing 10 uPVC double-glazed windows and a composite front door would pay around £8,500 for a mid-range installation from a FENSA-registered company. With the 0% VAT rate on energy-saving materials (in place until March 2027), the upfront cost drops to roughly £8,075. The installer offers a standard 10-year insurance-backed guarantee covering sealed unit failure, hardware and framework defects. According to the Energy Saving Trust, replacing single glazing with A-rated double glazing saves a typical semi-detached home around £195 per year on energy bills. The payback period on the windows alone is therefore roughly 41 years based on energy savings, though the primary value comes from improved comfort, reduced condensation and added property value. Over 25 years, the total energy savings reach approximately £4,875, not accounting for bill inflation.
| Item | Figure |
|---|---|
| Upfront cost after grants | £8,075 |
| Yearly savings | £195 |
| Payback period | 41 years |
| 25-year lifetime savings | £4,875 |
What homeowners often get wrong
The most common mistake is assuming all parts of the window or door are covered for the same length of time. Here are three frequent misconceptions that cost homeowners money and peace of mind.
- Believing the guarantee covers the glass for the full 10 years Many installers only cover sealed units for 5 years on the glass itself, with the 10-year guarantee applying to the frame and hardware. Check your paperwork, if the sealed unit fails after year 5, you could face a £150+ replacement bill.
- Thinking a 10-year guarantee means no maintenance is needed Guarantees almost always exclude damage from lack of maintenance, such as seized hinges from uncleaned tracks or rotten timber from unpainted frames. Skipping annual lubrication and seal checks can void your cover entirely.
- Assuming all guarantees are insurance-backed Only FENSA or CERTASS registered installers must offer an insurance-backed guarantee that protects you if the company goes bust. A non-registered fitter’s 10-year guarantee is worthless if they cease trading, leaving you with no recourse.
Quick reference
- Standard uPVC windows and doors come with a 10-year guarantee that is insurance-backed and FENSA-compliant.
- Timber or aluminium frames often have a 20-year profile guarantee but only 5–10 years on sealed glazing units and hardware.
- You must have the guarantee paperwork within 28 days of installation or the cover may not be legally enforceable.
- Annual maintenance like cleaning hinges and checking seals is a condition of most guarantees, skipping it can void the warranty.
- If your installer is not FENSA or CERTASS registered, your guarantee may not be insurance-backed and could be worthless within a few years.
Frequently Asked Questions
The typical guarantee period for new windows in the UK is 10 years. Ofgem and FENSA note that this is the industry standard for uPVC installations.
Yes, many 10-year guarantees are insurance-backed, meaning you are protected if the installer ceases trading. The Energy Saving Trust advises checking the small print for labour exclusions after the first year.
A standard 10-year guarantee covers manufacturing defects, sealed unit failure (condensation between panes) and hardware malfunction. It excludes damage from misuse, accidental breakage or lack of maintenance.
