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Resealing uPVC Windows: causes, signs and when repair is appropriate
Resealing uPVC windows is a common repair when a window frame and glass unit remain structurally sound but air or moisture begins entering the system. Many homeowners assume this means full replacement. In most cases, the issue relates to aging seals rather than the window itself, and even with the best efforts at resealing, sometimes a full replacement might be necessary.
This guide explains why seals fail, what symptoms matter, and how professional repair restores performance without changing the window.
Why the issue occurs
Window seals are flexible components designed to compress tightly between the frame and glazing unit. Over time, they degrade., often due to the improper application of sealant with a caulk gun.
Common causes include:
- Natural shrinkage of rubber gaskets
- UV exposure drying the material
- Frame movement due to temperature changes
- Drainage channels blocking and trapping moisture
- Previous poor installation tolerances
When seals lose elasticity, microscopic gaps form. Air and water vapour pass through. The window structure can still be intact, but its insulating performance drops.
Signs Resealing uPVC windows is needed
You rarely notice signs of seal failure immediately. The change is gradual.
Typical indicators include:
- Draughts around the opening sash
- Moisture marks along the bead line
- Internal condensation appearing at the edge of the panes of glass
- Glass looking hazy near the perimeter
- External noise becoming more noticeable
At this stage resealing double glazed windows often restores performance because the glazing unit itself is still functional.
Resealing uPVC windows : Repair vs replacement
Homeowners often assume fogging or draughts mean the window has “failed”. In reality there are levels of failure.
Repair is suitable when:
- Frames are straight and secure
- Hinges operate correctly
- Glass panes are intact
- Moisture occurs near the seal line only
Replacement becomes necessary when:
- Frames warp or crack
- Locks no longer align
- Structural movement prevents closing
Resealing double glazed windows focuses on restoring airtight compression, not altering the window design. It is a corrective maintenance task rather than an upgrade.
Safety and security implications
Seal failure affects more than comfort.
Gaps around glazing allow:
- Water ingress into internal chambers
- Gradual corrosion of reinforcement
- Reduced acoustic insulation
- Lower locking compression strength
In severe cases the sash does not sit firmly into the frame. Resealing windows restores proper closing pressure, which helps the locking points engage as intended and maintains the designed resistance to forced opening.
What happens after resealing uPVC windows
Condensation at the glass edge
Condensation at the edge of the glass usually means the perimeter seal has weakened, impacting your home’s comfort. Resealing restores the airtight barrier so indoor air no longer reaches the glazing edge. Moisture trapped between panes normally indicates a failed glazing unit and needs a different repair.
Expected lifespan after resealing
A resealed window can perform for many years because the issue is ageing seal material rather than structural damage. Longevity depends on weather exposure and use, but insulation performance generally returns close to the best option of the original level.
Repair compared with replacement
Repair targets a specific component rather than removing the full frame. When the frame and hardware remain serviceable, resealing corrects the fault and any condensation on the inside of the glass. Replacement is only needed if the structure is damaged or misaligned.
Security after seals are restored
Resealing can improve security. As seals shrink, locking points do not compress firmly against the frame. Restoring sealing pressure allows the sash to close tightly again so the locking system works as intended and resistance to forced movement improves.
How Futurglaze Approaches Window Repairs
Future Glaze inspects the frame alignment, drainage channels, hinges and glazing interface before deciding on repair. If the structure is sound, the work concentrates on restoring compression sealing around the sash and glass unit using simple steps so the window performs as originally designed.
Local service coverage
Future Glaze carries out repair work for homeowners across:
The regional climate involves high rainfall and coastal humidity. Seal deterioration often appears earlier in exposed locations, making maintenance-based repair particularly common.
Frequently Asked Questions
1. What causes window seals to fail?
Window seals fail mainly due to age and environmental exposure. Rubber gaskets gradually harden and shrink under sunlight and cold temperatures as well as temperature variation. Look for visible signs of wear such as movement of the building and repeated opening cycles which also reduce compression over time. Once elasticity reduces, air and moisture pass around the glazing edge. The window frame may still be structurally sound, which is why repair rather than replacement is often suitable.
2. Can failed seals affect heating efficiency?
Yes. Even small gaps allow warm air to escape and cold air to enter, impacting energy efficiency. The insulation performance of the glazing depends on maintaining an airtight perimeter. When seals weaken, heat transfer increases and rooms feel colder near the window. Restoring the seal returns the designed thermal barrier and reduces localized cold spots around the opening.
3. Is condensation always a sign of a broken glazing unit?
No. Condensation between panes indicates a broken seal and that the unit has failed internally, but moisture at the edges or on surrounding frame surfaces often points to perimeter sealing deterioration. Differentiating the location of condensation helps determine the correct repair. Many homeowners misinterpret this and replace windows unnecessarily.
4. Do aluminium windows need resealing too?
Yes. Aluminium systems also rely on flexible gaskets and compression seals. The material of the frame does not prevent seal ageing. Environmental exposure and repeated use affect aluminium window seals in the same way as uPVC systems, impacting the extent of the damage to the seals. The repair principle is identical: restore airtight compression around the glazing interface.
5. How do I know repair is still possible?
A professional inspection checks alignment, hinge wear, and frame stability. If the sash closes squarely and locking points engage correctly, repair remains viable, much like a credit broker assessing financial options. Structural distortion or cracked frames normally indicate replacement, but many performance problems, including issues with the double glazing window seal, occur long before that stage and can be resolved by maintenance-based repair.
