Double glazing is a staple of the modern UK home, providing essential thermal insulation and noise reduction. However, over time, seals can perish, glass can cr...
Repairing double glazing is often a significantly more cost-effective alternative to a full window replacement. By addressing specific issues like "misted" units or draughty frames, you can restore your home's energy efficiency and security without the upheaval of a complete installation.
What Does the Work Involve?
- Initial Inspection: Assessing the frames, beads, and gaskets to identify the cause of failure, such as blocked drainage or perished seals.
- Measurement: Precision measuring of the existing glass unit (height, width, and depth) to ensure the replacement fits perfectly within the frame.
- Unit Replacement: Removing the internal or external glazing beads, extracting the failed "blown" unit, and installing a new factory-sealed unit.
- Hardware Repair: Replacing or adjusting worn friction stays (hinges), broken handles, or faulty multi-point locking mechanisms.
- Weatherproofing: Replacing worn gaskets and clearing internal drainage channels to prevent future water ingress.
- Waste Removal: Safe disposal of broken or failed glass units, often through specialist recycling centres.
Typical Costs
| Item | Low £ | High £ | Notes |
|---|---|---|---|
| Call-out / Minimum Charge | £80 | £130 | Covers travel and the first 30-60 minutes of assessment. |
| Labour (per hour) | £50 | £80 | Varies by region; London and SE are typically higher. |
| Standard Sealed Unit | £45 | £150 | Small to medium clear glass units (supply only). |
| Specialist Glass (Toughened/K) | £90 | £250 | Safety glass or high-performance thermal coatings. |
| Window Handle Replacement | £25 | £60 | Includes part and labour for a standard handle. |
| Hinge/Friction Stay (Pair) | £60 | £120 | Includes parts and labour for standard uPVC windows. |
Several factors influence the final price, including the size of the glass, whether you require toughened safety glass (mandatory for certain heights), and the accessibility of the window. If the repair requires scaffolding or a cherry picker for high-level flats, costs will increase substantially.
How Long Does It Take?
- Hardware Adjustments: Fixing a stiff handle or adjusting a hinge typically takes 30 to 60 minutes.
- Glass Replacement: Once the unit is manufactured, the on-site fitting usually takes 1 to 2 hours per window.
- Lead Times: Sealed units are made to order; expect a 3 to 7 working day wait for the glass to be manufactured and delivered to the glazier.
DIY or Professional?
While minor tasks like changing a handle are manageable for a confident DIYer, replacing sealed units is best left to professionals. Glass is heavy, dangerous if broken, and incorrect measurements by even 1mm can prevent a unit from fitting or cause it to fail prematurely. Furthermore, professional repairs often come with a 5-10 year guarantee on the seal, which you won't get with a DIY job.
Choosing the Right Tradesperson
- Check Accreditations: Look for members of FENSA, CERTASS, or the Glass and Glazing Federation (GGF).
- Insurance: Ensure they hold valid Public Liability Insurance to cover any accidental damage to your property.
- Warranty: Always ask if they provide a guarantee on the "hermetic seal" of the new glass units.
- Questions to Ask:
- Is the replacement glass FENSA/Building Regs compliant?
- Do you include the disposal of the old glass in your quote?
- Will you be using high-performance "Warm Edge" spacer bars?
UK Regulations
- Document L: Repairs should maintain or improve the thermal efficiency of the dwelling.
- Document N (Safety Glass): Toughened or laminated glass must be used in "critical locations," such as doors, low-level windows (below 800mm), or windows near doors.
- FENSA/CERTASS: While a full window replacement requires a certificate, simple glass-only repairs generally do not, though work must still meet safety standards.
Common Problems
- Misting/Condensation: This indicates the "desiccant" inside the spacer bar is saturated and the seal has failed; the only fix is a new glass unit.
- Draughts: Usually caused by worn-out gaskets or hinges that have dropped, preventing the window from closing flush against the frame.
- Stuck Locks: Often a result of the window frame "dropping" over time, putting pressure on the locking bolts and causing the mechanism to jam.
- Water Leaks: Frequently caused by blocked "weep holes" or drainage channels at the bottom of the frame rather than a fault with the glass.
Frequently Asked Questions
Can you fix a misted window without replacing the glass?
No. Once the seal has blown and moisture is inside, the glass is permanently stained. "Drilling and drying" services exist but are often temporary fixes that don't restore the window's thermal properties.
Why do my double-glazed units fail?
Common causes include poor original installation, blocked drainage holes causing the unit to sit in water, or extreme temperature fluctuations causing the seals to expand and contract until they crack.
Do I need to replace the whole frame if the glass is broken?
Rarely. In almost all cases, the glass unit can be popped out of the frame and replaced independently, saving you thousands of pounds compared to a full replacement.
Is toughened glass necessary for all repairs?
It is legally required for any glass in a door, windows within 300mm of a door, or any window where the glass starts within 800mm of the floor level.
How can I tell if my hinges need replacing?
If you can see light through the side of the window when it's closed, or if you have to "lift" the handle to get the window to shut, the hinges (friction stays) are likely worn or bent.
What is a 'Warm Edge' spacer bar?
It is the plastic-based strip that separates the two panes of glass. Unlike old-fashioned aluminium bars, it doesn't conduct heat, which significantly reduces condensation around the edges of the window.
This guide was written with AI assistance and is intended for general information only. Prices are estimates based on UK averages and may vary by region. Always get at least three quotes and consult a qualified professional before starting any work.
