A guide to double glazing repair.

Repairing a "blown" or damaged window is often significantly cheaper than a full replacement. This guide covers everything from fixing misted units to replacing faulty hinges, helping you restore your windows to peak performance.

What Does the Work Involve?

• Initial Assessment: A specialist inspects the unit to determine if the failure is in the glass, the seal, or the frame mechanism.
• Measurement: For glass replacement, precise measurements of height, width, and unit thickness are taken to ensure a bespoke fit.
• Deglazing: The internal or external beads are carefully removed to extract the damaged Insulated Glass Unit (IGU).
• Cleaning and Prep: The window rebate is cleaned of old debris, and drainage holes are checked for blockages.
• Installation: The new double-glazed unit is positioned using packers to ensure it sits square and operates correctly.
• Finishing: Security beads are snapped back into place, and fresh silicone or gaskets are applied to ensure a watertight finish.

Typical Costs

Prices vary based on the size of the pane, the type of glass (e.g., toughened or Low-E), and your location in the UK. The figures below include VAT and typical labour charges for 2025/26.

Price Factors: Expect to pay more for scaffolding if the window is difficult to reach, or for specialist glass like acoustic laminate or decorative leaded designs.

How Long Does It Take?

• Initial Survey: 20–30 minutes to measure and diagnose the issue.
• Lead Time: 3–7 working days for the bespoke glass unit to be manufactured.
• Standard Pane Replacement: 45–90 minutes per window.
• Hardware Repairs: 30–60 minutes for handles, hinges, or locks.
• Full House Seal Refresh: 1 day for a standard semi-detached property.

DIY or Professional?

While replacing a handle is a straightforward DIY task, glass replacement should be left to the professionals. Handling large glass shards is hazardous, and incorrect measurements by even 1mm can result in a unit that won't fit or will fail prematurely.

Professional installers provide a guarantee (usually 5–10 years) on the seal of the new unit, which you won't get with a DIY attempt.

Choosing the Right Tradesperson

• Check Accreditations: Look for FENSA or CERTASS registered installers, or members of the GGF (Glass and Glazing Federation).
• Warranty: Ensure they offer a minimum 5-year guarantee against "misting" or seal failure.
• Specialism: Some firms specialise in "window surgery" or repairs rather than full replacements—these are often more cost-effective.

• Does the quote include the disposal of the old glass?
• Is the replacement glass "Low-E" (energy efficient) to match modern standards?
• Are you replacing the gaskets or just using silicone?

UK Regulations

• Part L (Conservation of Fuel and Power): Replacement glass must meet minimum thermal performance standards (U-values).
• Part K (Protection from Falling): Safety glass (toughened or laminated) is mandatory for windows in "critical locations," such as doors, low-level windows, or bathrooms.
• FENSA/CERTASS: While simple glass replacement doesn't usually require a building regulations certificate, full frame replacement does.

Common Problems

• Blocked Drainage: If water can't escape the frame through the bottom weep holes, the unit will sit in water and the seal will fail rapidly.
• Cheap Sealants: Using low-grade silicone instead of proper glazing gaskets can lead to leaks and draughts within months.
• Incorrect Packers: If the glass isn't "toed and heeled" correctly using plastic packers, the window sash will drop and catch on the frame.
• Mismatched Glass: Replacing one pane with standard glass when the rest of the house has a slight tint or leaded pattern can look unsightly.

Frequently Asked Questions