Exterior window repair

Repairing an existing window is often a more sustainable and cost-effective alternative to a full replacement. Whether you are dealing with a "blown" double-glazed unit, a stiff handle, or rotting timber sills, prompt action can extend the life of your windows by decades.

What Does the Work Involve?

• Initial Assessment: A thorough inspection of the frame, glass, and seals to identify structural issues, draughts, or failed "misted" units.
• Glazing Replacement: Removing the beads to swap out cracked or failed double-glazed units (IGUs) without replacing the entire frame.
• Hardware Repair: Replacing worn-out friction stays (hinges), broken handles, or faulty locking mechanisms to restore smooth operation and security.
• Timber Restoration: Removing soft, rotten wood from timber frames, treating the area with wood hardener, and rebuilding the profile with high-quality resin fillers.
• Draught-Proofing: Replacing perished rubber gaskets and applying fresh external perimeter sealant (mastic) to stop air and water ingress.
• Sash Realignment: Adjusting the "toe and heel" of a window sash to ensure it sits square in the frame and closes tightly.

Typical Costs

Prices for window repairs vary based on the frame material (uPVC, timber, or aluminium) and the height of the window. Working at height often requires additional equipment or a second operative for safety.

The total cost is largely driven by the "make and model" of the window hardware. While uPVC parts are generally standardised and cheap, older timber or bespoke aluminium windows may require specialist components that are more expensive to source.

How Long Does It Take?

• Glass Replacement: 30 to 60 minutes per unit (once the custom-sized glass has been manufactured and delivered).
• Hardware Repairs: 1 to 2 hours per window for handles, hinges, or gearbox replacements.
• Resealing & Draught-proofing: 1 to 3 hours for a standard-sized room.
• Timber Rot Repair: 4 to 8 hours, as resin fillers require curing time before they can be sanded and painted.
• Full Window Overhaul: 1 to 2 days for multiple windows involving glass, hardware, and sealant updates.

DIY or Professional?

Minor tasks like replacing a window handle or applying a bead of silicone sealant are manageable for a confident DIYer. However, most exterior window repairs require professional expertise to ensure the structural integrity and thermal performance of the unit remain intact.

Replacing double-glazed units involves handling heavy, fragile glass and requires precise "toe and heeling" to prevent the window from sagging. If done incorrectly, the window will not lock properly and the new seal may fail prematurely.

For timber repairs, professionals use industrial-grade epoxy resins that bond with the wood, whereas DIY fillers often pop out after one winter. Furthermore, any work involving gas-filled units or safety glass must meet specific UK standards that a professional will be familiar with.

Choosing the Right Tradesperson

• Check Accreditations: Look for installers registered with FENSA or CERTASS, as this ensures they work to UK Building Regulations.
• Specialism Matters: Some tradespeople specialise in uPVC, while others are experts in traditional timber sash restoration. Choose the one that matches your window type.
• Waste Removal: Ask if they are a registered waste carrier. Disposing of broken glass and old frames requires specific handling.
• Questions to Ask:
  • Is the replacement glass toughened or laminated to meet safety standards?
  • Do you offer a guarantee on the seal of the new double-glazed unit?
  • Is the cost of scaffolding included in the quote, or is that extra?
  • Can you match the existing hardware finish (e.g., polished chrome, brass, or black)?

UK Regulations

• Part L (Conservation of Fuel and Power): Replacement glass units should ideally improve or maintain the thermal efficiency of the window.
• Part K (Protection from Falling): Any glass in "critical locations" (e.g., low-level windows or windows in doors) must be safety glass (toughened or laminated).
• Listed Buildings: If your home is listed or in a Conservation Area, you may need Planning Permission even for minor repairs or like-for-like glass replacement.
• FENSA/CERTASS: While a full window replacement requires a certificate, simple repairs or glass swaps generally do not, though using a registered member ensures quality.

Common Problems

• Misted Windows: Caused by a breach in the unit's seal, allowing moisture to enter. This cannot be "cleaned" and requires a new glass unit.
• Dropped Sashes: If a window catches on the frame when closing, it usually means the glass wasn't packed correctly (toe and heeled) or the hinges are worn.
• Rotting Sills: Often caused by blocked "weep holes" or cracked paint. If left too long, the rot can spread to the structural wall plate.
• Draughty Frames: Usually due to perished rubber gaskets or the window being out of alignment, preventing a tight seal against the frame.
• Stiff Locks: Forced operation of a stiff handle can snap the internal gearbox. Regular lubrication with silicone spray can prevent this.

Frequently Asked Questions

Can you fix a misted double-glazed window without replacing the glass?

No. While some companies offer to "drill and dry" the unit, this is a temporary fix. Once the seal has failed, the desiccant inside the spacer bar is saturated. The only permanent solution is to replace the sealed glass unit itself.

How do I know if my window hinges need replacing?

If you see a gap on the hinge side of the window when it is closed, or if the window feels "notchy" or heavy when opening, the friction stays are likely bent or worn. This is a common cause of draughts.

Do I need to replace the whole frame if the wood is rotting?

Not necessarily. If the rot affects less than 20-30% of the frame, a specialist can often cut out the bad timber and use a resin repair system to restore it. If the rot is structural, a replacement is safer.

Is it possible to change the colour of my uPVC window frames?

While you can't easily "repair" the colour, uPVC can be professionally spray-painted. This requires specialist equipment and UV-resistant paint to ensure it doesn't peel or fade.

Why is there condensation on the outside of my new windows?

This is actually a sign of a high-performing window. It means the glass is so thermally efficient that the outer pane stays cold, allowing dew to form on the surface, just like it does on a car windscreen.

How much does it cost to fix a window that won't lock?

This usually costs between £80 and £150. It is often a simple matter of realigning the "keeps" or replacing a broken gearbox within the handle mechanism.