Draughty Windows: Common Causes and What Actually Fixes Them

Failing gaskets and worn hinges

The rubber gasket that seals a window when closed compresses and perishes over time, especially where it's exposed to sun and weather. Once it hardens, cracks or comes away from its track, it stops sealing properly and lets air straight through even when the window is fully closed and locked.

Worn hinges are a related but separate issue: as hinges wear, the sash or casement can sit slightly off its original position, meaning it no longer closes squarely against the seal even if the seal itself is fine. Both of these are often repairable without replacing the whole window, particularly on frames that are otherwise sound.

Dropped sashes

A dropped sash, where the opening part of the window has sagged slightly on its hinges or fittings, is one of the most common causes of a draught that seems to appear gradually over a couple of years. Even a small drop of a few millimetres can be enough to open a gap along one edge, since the locking mechanism no longer pulls the sash into full contact with the seal.

This is usually fixable by adjusting or replacing the hinges and checking the locking keeps, rather than needing a new window, provided the frame and glazing unit are otherwise in good condition.

Perished sealant and shrinking frames

The external sealant around a frame's perimeter, where it meets the wall, can shrink, crack or pull away after some years, and this is a different problem from the internal gaskets. It doesn't usually cause a noticeable draught inside the room directly, but it can let water and air into the cavity around the frame, which sometimes shows up as damp or a draught felt more at the reveal than at the glass itself.

Older frames, particularly some early uPVC installations, can also shrink very slightly over many years, opening tiny gaps at corner joints. This is harder to fix cosmetically and is one of the more genuine signs that a window may be approaching replacement age, especially if it's happening on several windows of a similar age at once.

Trickle vents versus genuine draughts

Trickle vents are designed to let a controlled, small amount of air through deliberately, for background ventilation, and it's easy to mistake this for a fault when it's actually working as intended. If a specific window feels draughty only near the vent and the vent slider is open, that's usually the vent doing its job rather than a problem with the window.

Closing the vent slider temporarily is a reasonable way to test this. If the draught disappears, it was the vent; if it persists elsewhere on the frame, the cause is more likely a seal, hinge or sash issue rather than ventilation.

Other draughts that get blamed on windows

Not every draught felt near a window actually comes from the window itself. Gaps around skirting boards, floorboards that have shrunk slightly, or an open chimney or unused flue nearby can all create air movement that's easy to misattribute to the nearest window, especially in older rooms with suspended timber floors.

It's worth checking these other sources before committing to window work, since sealing gaps at floor level or fitting a chimney draught excluder can sometimes solve what felt like a window problem for a fraction of the cost.

• Check floorboard gaps and skirting boards near the window
• Check for an open or unused chimney nearby
• Test with the trickle vent closed to rule it out
• Feel around the whole frame perimeter, not just the glass

Cheap fixes that genuinely work

Replacing a perished gasket, adjusting a hinge, or re-sealing a section of external sealant are all relatively inexpensive jobs that can solve a draught completely on a window that's otherwise in good structural condition. These repairs are worth trying first on newer or mid-age windows, since there's little to lose and a reasonable chance they'll resolve the issue.

Draught excluder strips and secondary glazing film are lower cost options too, though they're more of a stopgap on a window with an underlying fault, rather than a genuine fix for the root cause.

When replacement is the honest answer

If draughts are appearing across multiple windows of similar age, if frames are visibly warped, cracked or shrinking at the joints, or if the glazing units themselves have failed (shown by misting between panes), then repairs are unlikely to offer lasting value and replacement is usually the more sensible route. This is particularly true where a window is already old enough that hardware and seals are becoming hard to source.

A free survey can usually tell you fairly quickly which category a window falls into, and there's no harm getting an honest opinion before spending money on repairs that might only last a season or two.