Draughts round uPVC windows usually come from worn weather seals on the sash or frame, shrunken wedge gaskets around the glass, or a sash that no longer pulls tight against its seals because the hinges or keeps have worn. We replace the gaskets and seals that have failed and adjust the window so it closes firmly again. It is a repair to the existing window, not a replacement.
Which seals does a uPVC window have?
A typical uPVC casement window has two sets of rubber or synthetic seals doing different jobs:
- Weather sealsRun around the sash and/or the frame rebate. When the window is shut and locked, the sash presses against them to stop air and rain getting through the gap between opening and frame. Some systems use bubble seals, others brush (pile) seals, especially on sliding units.
- Glazing gasketsGrip the sealed glass unit on each side. Usually there is a fixed gasket on one side and a wedge gasket pushed in beside the glazing bead on the other. They keep the unit firm and stop water tracking past the glass.
- Glazing beadsThe clip-in uPVC strips that hold the glass unit in. They are not seals as such, but if they have been disturbed or are loose, the gaskets cannot do their job.
Signs your window seals need replacing
- A draught or cold spot you can feel with the back of your hand when the window is locked.
- Whistling or a moaning noise when it is windy.
- The window rattles in its frame when closed.
- Gaskets shrinking back from the corners, leaving a gap, or rubber that is cracked, hard or flattened.
- Black mould along the rubber, which often means water is sitting where it should not.
- Dust or dirt lines on the inside sill or the inner face of the frame, showing where air is getting through.
If water is getting in rather than just air, the cause is not always the seals; our leaking window repair page looks at drainage, sealant and other routes.
Why do window seals fail?
Seals and gaskets compress and harden with age and sunlight, and some older materials shrink, which is why gaps tend to open up at the corners first. A sash that has dropped on worn hinges stops compressing the seal evenly, so you get a tight side and a loose side. Keeps that have been moved or worn can stop the locking cams pulling the sash in. Paint, filler or silicone smeared on seals also stops them working. On exposed coastal homes, constant wind and sun can wear seals sooner.
That is why we look at the whole window. Fitting new seals to a sash that does not close properly only moves the draught. Often the best fix is a combination of new seals and a hinge or keep adjustment, which ties in with our window hinge repair work.
How we replace window seals
- Find the leak. We check where the draught is coming from and whether the sash closes and locks evenly.
- Identify the seal profile. uPVC systems use many different seal shapes. We match the profile to the groove so the new seal sits properly.
- Adjust if needed. Hinges, keeps and locking cams are adjusted so the sash compresses the new seals evenly.
- Fit the seals and gaskets. Old seals are pulled out of their grooves and new ones fitted, with corners finished neatly. Wedge gasket work involves the glazing beads, so we handle it with care around the glass unit.
- Test. We close and lock each window and check for draughts and rattles before we leave.
What seals cannot fix
New seals will not cure condensation between the panes of glass. That means the sealed unit itself has failed, and the answer is a new unit, covered on our misted double glazing repair page. Seals also will not help with condensation on the room side of the glass, which is about humidity and ventilation; keeping trickle vents open, or fitting them where there are none, usually helps more.
Window seal replacement across Merseyside
We replace seals across Liverpool and Merseyside. Draughty first-generation uPVC windows are common in inter-war and post-war semis in areas such as Childwall and Maghull, while homes near the coast in Formby see seals worked hard by wind-driven rain. It is often booked alongside other double glazing repairs on Merseyside.
What affects the cost?
The number of windows, the length and type of seal, whether wedge gaskets around the glass need replacing as well as weather seals, and whether hinges or keeps need adjusting or replacing. Less common seal profiles can take longer to source. We quote in writing after a look at the windows.
Draughty windows?
Tell us which windows and what you are noticing. Call 07777 659786 or use the form and we will call you back to arrange a visit from our local window repair team.
Frequently asked questions
Can you replace the rubber seals on uPVC windows?
Yes. Most uPVC windows have replaceable weather seals and glazing gaskets that sit in grooves in the frame and sash. The new seal has to match the groove profile, as there are many different types. We identify the profile first so the replacement fits snugly and compresses properly.
Why is there a draught coming from my closed window?
Common causes are worn or shrunken seals, a sash that has dropped on worn hinges so it no longer closes evenly, and keeps that do not pull the window tight. Sometimes a trickle vent is simply open. We check which it is before replacing anything.
Is replacing seals cheaper than replacing the window?
Generally, yes. If the frame and glass units are sound, new seals and an adjustment usually cost a fraction of a new window and can make a noticeable difference to draughts and noise. We do not supply new windows, so our advice is about getting the most from the ones you have.
What is the black mould on my window seals?
Mould on seals usually means moisture is sitting on them, often from condensation on the room side of the glass or water not draining from the frame. Cleaning it off and improving ventilation helps. If the rubber has perished or water is getting past it, the seal may need replacing.
Will new seals stop condensation between the panes?
No. Condensation between the panes means the sealed glass unit has failed and moist air has got into the cavity. Window seals and gaskets are separate from that edge seal. The fix is a new sealed unit made to measure for the existing frame.
How long does window seal replacement take?
It depends on how many windows and which seals. Replacing the weather seals on a single window is usually a short job, while wedge gaskets around the glass take longer because the glazing beads are involved. If the seal profile is unusual, we may need to order it and return.