A draughty window is not automatically a failed window. In the majority of houses we visit, the cold air is coming from a perished gasket, a sash that has dropped out of adjustment, or a gap in the external sealant — all of which are cheap fixes on an otherwise sound frame.
This guide takes you through finding the source and dealing with it, and is honest about the point at which the frame really does need replacing.
How to find and fix a draughty window: step by step
- 1
Find the draught
On a windy day, move a lit candle or a strip of tissue slowly around the perimeter of the closed window — along the opening joint, around the frame edge where it meets the wall, and around any trickle vent.
- 2
Check the gaskets
Open the sash and press the black rubber seal. It should be soft and spring back. Hard, shrunken or missing sections let air straight through and can be replaced by the metre.
- 3
Adjust the hinges and keeps
If the sash only seals on one side, the friction stays or the lock keeps need adjusting so the sash compresses evenly onto the gasket.
- 4
Reseal the outside
Rake out cracked or shrunken external sealant, clean the surface and apply a low-modulus neutral-cure silicone in a continuous bead.
- 5
Deal with the inside
Fill gaps behind loose internal trims with decorator's caulk, or refit the trim if it has pulled away from the plaster.
- 6
Reassess
Repeat the candle test. If the draught persists through the frame itself or the frame is rotten or distorted, replacement is the answer.
Where draughts actually come from
The opening joint
This is the gap between the sash and the frame, sealed by a rubber gasket. Gaskets last roughly ten to fifteen years before they harden. Replacement gasket is sold by the metre, pushes into the groove, and is genuinely a job most people can do with a screwdriver and half an hour.
Hinge and lock adjustment
uPVC windows compress onto their seals. Over time, hinges wear and the sash drops a few millimetres, so it seals top and not bottom. Most locking keeps have a cam that can be turned to pull the sash tighter. Turn them a small amount at a time — over-tightening makes the handle stiff and wears the mechanism.
The frame-to-wall joint
Outside, the frame is sealed to the reveal with silicone. That bead shrinks and cracks, particularly on a sunny elevation, and once it opens up wind drives straight through. This is one of the most common causes of a 'draughty window' where the window itself is fine.
Trickle vents
Trickle vents are supposed to let air in — that is their job, and closing them permanently causes condensation and mould. Check the internal flap closes properly and that the vent is not simply broken.
What each fix costs
| Fix | DIY cost | Typical trade cost | Difficulty |
|---|---|---|---|
| Replacement gasket (per window) | £4 – £10 | £40 – £80 | Easy |
| Hinge and keep adjustment | £0 | £45 – £90 call-out | Easy to moderate |
| New friction stays / hinges | £12 – £30 per pair | £70 – £130 | Moderate |
| Re-sealing externally (per window) | £8 – £15 | £50 – £100 | Moderate, ladders |
| Internal caulking and trims | £6 – £12 | £40 – £80 | Easy |
| Secondary glazing panel | £90 – £250 | £200 – £450 | Moderate |
| Full window replacement | n/a | £450 – £900 | Trade only |
Fixes that are not worth doing
- Foam self-adhesive strip on a uPVC window — it stops the sash compressing properly and usually makes the seal worse.
- Expanding foam squirted into the frame-to-wall gap from outside; it holds water against the frame.
- Sealing the window shut with silicone around the opening joint. It will need cutting out and it prevents drainage.
- Blocking trickle vents with tape. You will trade a draught for condensation and mould.
When the window has to be replaced
Replacement becomes the sensible answer when the frame itself is the problem: rotten timber, welded uPVC corners splitting open, a frame bowed enough that the sash cannot be pulled square, or single glazing where the cold radiating off the glass is what you are actually feeling.
A useful test is cost against remaining life. Spending £150 to get five more good years out of a window is worth it. Spending £150 on a frame that is coming out in eighteen months is not.
Getting someone to look at it
If you would rather have it checked than climb a ladder, most installers will do a draught and adjustment visit for a modest call-out. We cover Cumbernauld, Glasgow, Falkirk, Stirling and the wider Central Scotland area, and we will tell you if a £60 adjustment does the job — you can reach us on 07538 882579.
Common questions
Usually because that sash has dropped or its gasket has perished, or because it is on the weather elevation and the external sealant has failed first.
Want a straight answer on your own windows or doors?
DM Installations fits and repairs windows and doors across Central Scotland — Cumbernauld, Glasgow, Falkirk, Stirling and the surrounding towns. Free survey, written quote, and an honest answer on whether you need a repair or a replacement.
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