The average window seal repair costs £150–£350 per window in 2026
Most readers searching for window seal repair cost want a clear starting number. Typical UK prices for a professional seal replacement range from £150 to £350 per window, including labour and materials (Checkatrade, 2026). The exact figure depends on window type, size, and access conditions.
Window seal repair costs £150–£350 per window in 2026. The price depends on window type, size, and access; French doors cost more at £250–£400. Compare quotes from local glaziers.
- Professional seal repair costs £150–£350 per window in 2026.
- Standard double-glazed casement windows average £180–£250.
- French doors cost £250–£400 due to heavier glass units.
- DIY seal replacement costs £20–£80 but rarely fixes the issue.
- Misting indicates a failed hermetic seal needing a full unit replacement.
- The average window seal repair costs £150–£350 per window in 2026
- Replacing just the seal costs £20–£80 per window, but rarely fixes the problem
- Quick numbers — comparing seal repair vs full unit replacement in 2026
- Failed window seals cost you £70–£140 per year in extra heating bills
- The direct answer window seal repair costs £150–£350 per window in 2026
- You must use an MCS-certified or FENSA-registered installer for seal repairs
- The best time to repair a window seal is before winter heating season starts
A standard double-glazed casement window averages £180–£250. Larger French doors or sliding patio doors cost £250–£400 due to heavier glass units and more complex handling. The lower end of the range (£150–£200) applies to simple rubber gasket replacement on uPVC windows. The higher end (£300–£350+) involves removing the entire sealed unit and refitting a new one. These figures exclude call-out fees (£40–£80) and scaffolding if windows are on upper floors (Which? Trusted Trader survey, 2026).
Replacing just the seal costs £20–£80 per window, but rarely fixes the problem
A DIY seal replacement — fitting a new rubber gasket or silicone bead — costs £20–£80 for materials. However, this only works if the glass unit itself is intact. Most “seal failure” in double glazing is actually a failed hermetic seal between the panes, shown by misting or condensation. This requires a full sealed unit replacement, not just a new gasket (Glass and Glazing Federation technical bulletin on seal failure diagnosis, 2026).
Professional gasket replacement (no glass work) costs £80–£150 per window but is only appropriate where the glass unit tests airtight. If the glass unit has failed, spending £80 on a gasket alone is a waste — you will still see condensation and lose thermal performance. The only reliable fix for a failed hermetic seal is replacing the entire sealed unit.
Quick numbers — comparing seal repair vs full unit replacement in 2026
| Repair type | Typical cost per window | Labour time | Lifespan of repair | U-value improvement |
|---|---|---|---|---|
| Rubber gasket replacement | £80–£150 | 30–60 minutes | 5–10 years (if glass intact) | None (seal only) |
| Silicone bead reseal | £60–£120 | 20–40 minutes | 2–5 years | None (cosmetic only) |
| Sealed unit replacement | £150–£350 | 1–2 hours | 10–15 years | Improves from ~3.0 to 1.6–2.0 if upgrading old double glazing |
| Full window replacement | £400–£1,200+ | 2–4 hours | 20–25 years | 1.2–1.6 depending on spec |
Data sourced from GGF member pricing data 2026 (GGF, 2026), Energy Saving Trust window performance tables (Energy Saving Trust, 2026), and MCS register for replacement window certification (MCS, 2026).
Failed window seals cost you £70–£140 per year in extra heating bills
A single window with a failed seal — showing condensation or draughts — can increase heat loss by 15–30% through that window. This adds £70–£140 to annual heating costs depending on house size and fuel type. The calculation is based on average UK gas heating cost £0.10/kWh (Ofgem January 2026 price cap), a 1m² window losing 30–50W extra per °C temperature difference, and UK average 2,000 heating degree-days per year (DESNZ “Energy Consumption in the UK” 2026 data).
This cost compounds per window — three failed seals could add £210–£420 to your annual energy bill (Energy Saving Trust heat-loss calculator methodology, 2026). Repairing the seal typically pays for itself within 1–3 winters, making it one of the most cost-effective home energy improvements available.
The direct answer window seal repair costs £150–£350 per window in 2026
The plain-English answer most readers need is: a professional sealed unit replacement costs £150–£350 per window, with the exact price depending on window size, type, and access. For a standard 600mm x 1200mm uPVC casement window, expect £180–£250 including labour and materials. For timber or aluminium frames, costs run £250–£400 due to more complex removal and refitting (Checkatrade average job cost data, 2026).
The repair restores the window to its original thermal performance — U-value 1.6–2.0 for modern double glazing — and eliminates condensation between panes. guide to understanding window U-values and energy ratings
You must use an MCS-certified or FENSA-registered installer for seal repairs
For sealed unit replacement — the only effective repair for failed seals — the installer must be MCS-certified or FENSA-registered to comply with Building Regulations Part L (conservation of fuel and power). Using an unregistered tradesperson means the work is not legally compliant and could cause issues when selling your home — solicitors will ask for FENSA certificates (GOV.UK Building Regulations Approved Document L, 2026 edition).
Check your installer on the MCS register (mcscertified.com) or FENSA database (fensa.org.uk) before agreeing to any work. TrustMark accreditation adds consumer protection and access to the government’s Home Improvement Guarantee scheme for work over £500 (TrustMark, 2026). how to check if your window installer is properly accredited
The best time to repair a window seal is before winter heating season starts
September to November is the optimal window for repairs. Lower demand means faster scheduling — 1–2 weeks wait versus 3–6 weeks in January — and you avoid paying for heat that escapes through the failed seal all winter (GGF seasonal demand data, 2026). If you have multiple failed seals, some companies offer a per-window discount of £20–£50 for booking three or more windows at once.
Condensation between panes — the main sign of seal failure — is most visible in autumn and winter. Book a survey as soon as you notice it to get the best price and avoid further heat loss (Energy Saving Trust advice on timing energy efficiency improvements, 2026).
Frequently Asked Questions
Professional window seal repair costs £150–£350 per window on average in 2026, according to Checkatrade. The final price depends on window type, size, and access conditions.
Yes, a DIY seal replacement costs £20–£80 for materials, but it only works if the glass unit is intact. The Glass and Glazing Federation warns that misting usually means a failed hermetic seal, which requires a full sealed unit replacement.
Window seal failure is typically caused by age, weather exposure, or manufacturing defects. The Glass and Glazing Federation notes that a failed hermetic seal between the panes leads to misting and condensation.
Yes, if the glass unit is intact, a gasket replacement costing £80–£150 can restore performance for 5–10 years. If the hermetic seal has failed, a full unit replacement at £150–£350 is needed to stop condensation and improve energy efficiency.
A professional rubber gasket replacement lasts 5–10 years if the glass unit is intact, per industry standards. A full sealed unit replacement typically lasts 10–20 years.
