How to Stop Draughts Around Windows and Doors: Beginner’s Guide

On the first properly windy evening of the year, close a window and run the back of your hand slowly around the edge of the frame. Start at a bottom corner, work up the hinge side, across the top and down past the handle. Most of us find the same thing: a thin, steady stream of cold air in one or two places and nothing much anywhere else. Not a dramatic hole, just a few small, unremarkable gaps doing all the damage.

The fix is usually inexpensive and well within reach of someone who has never tried it before. It needs patience in the finding, before any money is spent on seals. Once you know where the air is coming in, most draughts can be dealt with in an afternoon with a knife, a cloth and a roll of seal.

Find the draught before you buy any seals

Wait for a breezy day, then work methodically rather than wandering from window to window. Feel along the closing face of the window, the part where the sash presses against the frame, not just the face you can see from the sofa. A tissue held loosely between finger and thumb will flutter where a gap exists, and a sliver of daylight under a closed sash is a reliable clue on a bright morning. Leave the candle in the drawer; an open flame near curtains is not worth the risk.

It also helps to know what you are feeling for. A draught is moving air. A cold pane or a chilly aluminium frame is simply a cold surface, and sealing it will not change much. If the window feels cold but your hand detects no movement, the problem is the glass or the frame material, not the gaps.

Some spots are easy to overlook:

The joint where the frame meets the plaster or render, often hidden behind a trim or a window board
The underside of the sill, outside, where old mastic cracks and pulls away
The meeting rail in the middle of a sliding sash window
Letterboxes, keyholes and the gap under a door, which together can move more air than a whole window
Loft hatches and unused extractor fan outlets on the same wall

And be ready for a false alarm. Air has to enter a house somewhere and leave somewhere else, so a running kitchen extractor fan will pull cold air through every weak point in the building, and the window nearest the fan tends to take the blame. If a draught disappears when the fans are off and the internal doors are open, you are chasing pressure, not a broken seal.

The short shopping list

You do not need much, and you certainly do not need everything at once. Buy after you have found the gaps, not before.

Self-adhesive foam tape for gaps of roughly 3–5 mm. Cheap and quick, but it compresses permanently after a season or two.
EPDM or silicone rubber seal for 5–8 mm gaps. It springs back after being squeezed, which makes it the better choice on a window you open daily.
Brush or pile strip for sliding sashes and any gap of uneven width.
Flexible frame sealant and a cartridge gun for exterior joints that move slightly.
Acrylic caulk for interior cracks that will be painted over.
A door-bottom brush or automatic drop seal, which lifts clear as the door opens and is kinder to uneven floors.
Basics: a sharp craft knife, methylated spirit and a cloth, screwdrivers, and an Allen key set for uPVC hardware.

Sealing the two kinds of gap at a window

The joint between frame and wall

A hairline crack where the frame meets the wall is often the biggest single leak in a room, and it is invisible because the trim covers it. Rake out anything loose, then run a bead of flexible frame sealant into the joint, pressing it in rather than smearing it across the surface. Indoors, acrylic caulk is fine because it can be painted. Outdoors, use an exterior-grade sealant that stays flexible. If the gap is deep enough to swallow the nozzle, fill it first with a low-expansion foam made for windows and doors, trim it back once cured, then seal over the top. Ordinary expanding foam will bow a thin frame if you overfill it.

The gap where the window opens

Clean the surfaces with methylated spirit and let them dry, or nothing will stick for long. Fit the seal to the frame face that the sash closes onto, so the window compresses it when you turn the handle. Foam tape and rubber seals go on the flat rebate; brush strip is better along sliding sashes and anywhere the gap varies in width. On uPVC frames, keep the small drainage slots at the bottom clear. They look like gaps but they let water out, and blocking them leads to damp inside the frame.

If the window becomes hard to close after you add a seal, the seal is too thick, not the window's fault. Go thinner rather than forcing the handle.

Adjust before you seal

A surprising number of draughty windows are not worn out, just out of alignment. On uPVC, the hinges usually have adjustment screws and the keeps on the frame can be moved a little to pull the sash tighter against the weather seal. Turn a quarter turn at a time and test the handle after each one, because it is easy to overshoot and make the window stiff. On timber casements, check for loose hinge screws, a hinge that has been packed out over the years, or a strike plate that stops the catch engaging fully.

Sliding sashes deserve their own look. If the lower sash rattles in the wind, the staff beads may need adjusting or renewing, and brush seals along the parting bead will do more than any amount of tape around the frame. And if a sash is visibly warped or the timber is soft at the bottom corners, stop: a seal will not close a gap that keeps changing shape. At that point a window installer is the sensible call.

Doors lose more heat than windows

The gap under an internal door is there for a reason, but the one under an external door is not. Fit a brush strip if the floor is flat, or an automatic drop seal if it is not. Add a letterbox flap, a cover over the keyhole, and check that the lock actually pulls the door against its frame; a door that rattles in the wind is often a strike plate set a millimetre too far back. A fabric excluder across the bottom is a perfectly respectable short-term answer while you get round to the proper job.

One caution: if the door is a fire door, anything you add must not stop it closing fully against its stops, and the intumescent strips and closer should be left alone. Ask a qualified fitter if you are unsure.

Do not seal everything

A house needs air. Trickle vents on windows should be open, air bricks should be clear, and kitchen and bathroom fans should be able to draw replacement air from somewhere. If a room contains a gas appliance, an open fire or a wood burner, never block a vent or air brick that feeds it; ask a qualified heating engineer before changing anything in that room. Seal a home too tightly and the moisture from cooking and showering has nowhere to go, which shows up as condensation on the glass and mould in cold corners.