Seal & fix window leaks.

Professional window sealing goes beyond simply squiring silicone into a gap. It involves identifying the root cause of ingress—whether it is failed gaskets, blocked drainage channels, or degraded external pointing—and ensuring the thermal envelope of your home remains intact.

What Does the Work Involve?

• Diagnostic Inspection: Identifying the leak source using thermal imaging or water testing on frames, gaskets, and masonry.
• Surface Preparation: Mechanical removal of failed silicone, brittle glazing tape, or loose mortar.
• Cleaning: Degreasing surfaces with specialist cleaners to ensure the new sealant bonds correctly.
• Gasket and Bead Repair: Replacing shrunk rubber gaskets or damaged glazing beads that hold the glass in place.
• Sealant Application: Applying high-specification low-modulus neutral-cure silicone or polyurethane sealant to external joints.
• Drainage Clearing: Checking and clearing internal "weep holes" that allow water to exit the frame.

Typical Costs

The total cost is primarily driven by accessibility and the condition of the frames. While a ground-floor uPVC reseal is straightforward, repairing rotted Victorian sash windows or working at height on a townhouse will significantly increase labour and equipment costs.

How Long Does It Take?

• Single window reseal: 1–2 hours.
• Full house external reseal: 1–2 days (depending on the number of openings).
• Timber cill or bead replacement: 3–5 hours per window.
• Drying time: Most modern sealants are "skin-over" in 30 minutes but require 24 hours to fully cure.

DIY or Professional?

Homeowners can often tackle ground-floor resealing if they use the correct materials. However, identifying the *exact* entry point of water is notoriously difficult, as leaks often travel through the wall cavity before appearing inside.

Professional tradespeople use "Low Modulus" sealants which offer better movement accommodation than standard DIY-store silicone, preventing the seal from snapping during temperature changes.

For any work above the ground floor, professional hire is essential for safety. Furthermore, if your windows are still under a FENSA or CERTASS warranty, DIY repairs may void your protection.

Choosing the Right Tradesperson

• Check Accreditations: Look for FENSA, CERTASS, or GGF (Glass and Glazing Federation) membership.
• Verify Insurance: Ensure they hold Public Liability insurance (minimum £1m-£2m) for working on your property.
• Ask about "Neutral Cure": Ask what sealant they use; neutral-cure silicone is superior for uPVC and stone as it doesn't cause discolouration.
• Warranty: A reputable pro should offer a 12-month guarantee on leak repairs.

UK Regulations

• Part L (Conservation of Fuel): Repairs must not degrade the thermal performance of the window.
• Part F (Ventilation): Sealing work must not accidentally block trickle vents or essential background ventilation.
• Working at Height: All contractors must follow HSE guidelines; ladder work is often restricted for long-duration repairs.

Common Problems

• Applying "Wet on Wet": Applying new sealant over old, damp, or dirty silicone leads to immediate failure.
• Blocked Drainage: Many "leaks" are actually caused by dust and debris blocking the drainage channels inside the uPVC frame.
• Wrong Sealant: Using "Acetoxy" silicone on natural stone or certain metals can cause chemical etching and staining.
• Ignoring the Masonry: Water often enters through cracked mortar joints (pointing) around the window rather than the window itself.

Frequently Asked Questions