What the Standard Double Glazing Guarantee Covers in the UK
A typical double glazing guarantee in the UK covers the sealed unit (glass and gas) for 10 years and the frame and hardware for 5–10 years, but installation defects are often only covered for the first two years. The terms are set by the Glass and Glazing Federation (GGF) Consumer Code, which most reputable installers follow (GGF, 2026).
A standard double glazing guarantee in the UK covers the sealed unit for 10 years and frames for 5–10 years. Installation workmanship is typically only guaranteed for 1–2 years, so check your installer's terms carefully.
- Sealed units are covered for 10 years against misting or condensation.
- Frame materials guaranteed for up to 10 years, timber shorter at 5–7 years.
- Hardware like handles and locks covered for 5–10 years typically.
- Installation workmanship only guaranteed for 1–2 years by most fitters.
- Accidental damage, misuse, and normal wear and tear are excluded.
- What the Standard Double Glazing Guarantee Covers in the UK
- What Is NOT Covered by a Double Glazing Guarantee
- Quick Numbers – Typical Guarantee Durations and Coverage
- How to Make a Claim on Your Double Glazing Guarantee
- The Direct Answer – What Does a Double Glazing Guarantee Actually Cover in the UK?
- Eligibility and How to Verify Your Installer’s Guarantee
- How Long Does a Double Glazing Guarantee Last in the UK?
Glass sealed-unit failure, misting or condensation between the panes caused by a broken seal, is almost always covered for 10 years. Frame materials (uPVC, timber, aluminium) are typically guaranteed against rot, warping, or discolouration for up to 10 years, though timber frames may be shorter at 5–7 years. Hardware such as handles, hinges, and locks is covered for 5–10 years depending on the manufacturer. Installation workmanship, which covers defects from fitting (e.g., draughts, gaps, or poor alignment), is normally guaranteed for only 1–2 years (FENSA, 2026).
What Is NOT Covered by a Double Glazing Guarantee
No guarantee covers everything. Accidental damage, misuse, or neglect of windows or doors is excluded. Condensation on the external or internal surfaces of the glass, as opposed to between the panes, is not covered because it relates to ventilation and humidity, not a manufacturing fault (GGF, 2026).
Fading or discolouration of frames caused by direct sunlight or environmental factors is typically excluded, as is normal wear and tear of moving parts after the initial period. If a handle becomes stiff after five years of use, that is wear and tear, not a defect. Some guarantees also exclude damage from building movement, such as subsidence, or from incorrect cleaning products (Citizens Advice, 2026).
Quick Numbers – Typical Guarantee Durations and Coverage
| Component | Typical Guarantee Length | What Is Covered |
|---|---|---|
| Sealed unit (glass) | 10 years | Failure of seal (mist, condensation between panes) |
| uPVC frame | 10 years | Rot, warping, discolouration |
| Aluminium frame | 10 years | Corrosion, structural failure |
| Timber frame | 5–10 years | Rot, fungal decay |
| Hardware (handles, locks, hinges) | 5 years | Mechanical failure |
| Installation workmanship | 1–2 years | Defects from fitting |
These durations are typical across the industry, as set out by the GGF Consumer Code and FENSA guidance (FENSA, 2026). Some premium manufacturers offer extended periods of 15–20 years on the sealed unit.
How to Make a Claim on Your Double Glazing Guarantee
If a defect appears, contact the original installer first. Your contract is with them, not the manufacturer, so they are responsible for rectifying the issue under the workmanship guarantee (Citizens Advice, 2026). Provide proof of purchase, an invoice, guarantee certificate, or digital receipt, and document the defect with clear photos and a written description of the problem.
If the installer has ceased trading, contact the manufacturer directly. Many guarantees are backed by a third-party insurance scheme, such as GGF Insurance, which provides cover even if the original company goes out of business (GGF, 2026). Check your guarantee certificate to see if it includes such a scheme. If not, you may need to pursue a claim under the manufacturer’s own warranty.
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The Direct Answer – What Does a Double Glazing Guarantee Actually Cover in the UK?
A double glazing guarantee in the UK covers the sealed unit (glass and gas) for 10 years against failure of the seal, the frame against manufacturing defects for 10 years, and hardware for 5–10 years, but installation workmanship is typically only covered for 1–2 years (GGF, 2026). This means that if mist appears between the panes within a decade, the sealed unit is replaced for free. If a hinge fails after three years, it is likely covered under the hardware guarantee. However, if a window is poorly fitted and draughty after 18 months, the installer is responsible under the workmanship guarantee, but after two years you may have to pay for repairs yourself.
The key distinction is between manufacturing defects (covered for longer periods) and installation faults (covered for shorter periods). Always check the specific terms in your guarantee certificate, as some manufacturers offer extended cover on premium ranges (FENSA, 2026).
Eligibility and How to Verify Your Installer’s Guarantee
To ensure your guarantee is valid, check that the installer is registered with FENSA or CERTASS. Registration with these bodies means the installation meets Building Regulations, and the guarantee is recognised as enforceable (GOV.UK, 2026). If the installer is not registered, the guarantee may not be worth the paper it is written on.
Verify that the manufacturer’s warranty is backed by a third-party insurance scheme, such as GGF Insurance. This ensures cover continues even if the installer goes out of business. At the time of installation, request a written guarantee certificate that states the start date, duration, and exactly what is covered for each component. Without this document, proving a claim becomes difficult (GGF, 2026).
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How Long Does a Double Glazing Guarantee Last in the UK?
The sealed unit (glass) is typically guaranteed for 10 years, but some premium manufacturers offer 15 or 20 years. Frame and hardware guarantees range from 5 to 10 years, with timber frames often having shorter periods of 5–7 years due to natural material variability (GGF, 2026). Installation workmanship guarantees are usually 1–2 years, though some installers may offer up to 5 years as a competitive differentiator.
ONS housing stock data shows the average UK home has 12–15 windows (ONS, 2026), so the total cost of replacing a sealed unit under guarantee could be significant. A 10-year guarantee on the sealed unit is the industry baseline, but always check the fine print, some guarantees reduce cover after year five or exclude certain types of failure, such as argon gas loss without visible misting.
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Frequently Asked Questions
A standard double glazing guarantee covers the sealed unit for 10 years, the frame for 5–10 years, and hardware for 5–10 years. Installation defects are usually covered for only 1–2 years, as per the Glass and Glazing Federation (GGF) Consumer Code.
Most guarantees last 10 years for the sealed unit and 5–10 years for frames and hardware. The installation workmanship guarantee is shorter, typically 1–2 years, as set by FENSA standards.
Yes, condensation or misting between the panes caused by a broken seal is covered by the sealed unit guarantee, usually for 10 years. However, condensation on the outside or inside of the glass is not covered, as it relates to ventilation and humidity.
Exclusions include accidental damage, misuse, neglect, and normal wear and tear. Fading from sunlight, damage from building movement like subsidence, and condensation on external or internal surfaces are also not covered, as explained by Citizens Advice.
Many double glazing guarantees are transferable to new homeowners, but you must check the terms. The Glass and Glazing Federation (GGF) recommends confirming transferability with the installer before sale.
