How to Find and Seal the Draughts in Your House

Nearly every draught is a gap you can already find with your hand

A draughty house feels like a mystery until you go looking for it properly, and then it turns out to be four or five gaps you could have found in ten minutes, because the back of your hand is a surprisingly good instrument for this. Wait for a cold still day, shut the house up, and walk around slowly with your hand held near the edges of things.

The places worth checking first are the gap under an external door, the meeting edge where a pair of doors come together, the frame around an older timber window, the join where a wall meets the floor in an unlined room, and the space around an evaporative cooler outlet in the ceiling. If you would rather see it than feel it, hold a lit candle or a stick of incense near the edge and watch which way the smoke leans.

Match the seal to the gap, because they are not interchangeable

Under a door you want a brush strip or a spring-loaded automatic seal that screws onto the bottom of the door itself. A brush strip is cheap and forgiving of an uneven floor, so it suits an old house where nothing is quite square. An automatic seal drops down when the door closes and lifts as it opens, so it clears a rug or a tiled threshold that a brush would drag on.

Around a door or window frame, the gap is usually between the frame and the wall rather than between the door and the frame, and that one gets filled rather than sealed. Acrylic gap filler goes in with a caulking gun, takes paint over the top of it once it has cured, and stays flexible enough to cope with a timber frame moving through the year.

Outside, or anywhere that gets wet, use a silicone rather than an acrylic filler, because acrylic will not hold up to weather for long. Silicone will not take paint, so choose a colour that suits what it is going onto rather than assuming you will paint over it later.

The gap where a window sash meets the frame is the one people get wrong, because filling it stops the window opening. That gap wants a compressible seal on the frame so the sash closes onto it.

One thing to be careful about before you seal everything up

Do not block a fixed wall vent in a room that has an unflued gas heater in it. Those vents are there to supply combustion air and to let the products of burning get away, and sealing one up because it feels draughty is genuinely dangerous rather than just unwise. The same goes for a vent serving a gas hot water unit or a wood heater. If you are not certain what a particular vent is doing, leave it alone and ask a licensed gas fitter, because that is not a guessing sort of question.

An open fireplace that has been properly disconnected is a different matter, and a chimney sealing balloon or a simple board cut to fit will stop a surprising amount of warm air disappearing up it.

The fixes that cost nothing

A heavy lined curtain that reaches past the bottom of the window rather than stopping at the sill will do more than most people expect, and closing the doors on rooms nobody is using shrinks the volume you are trying to heat. A rug over a bare floorboard room takes the edge off the cold coming up between the boards, which is a different problem from a draught but it feels like the same one.

Shop related products

• GSA Acrylic Gap Filler 450g. For the gap between a frame and the wall, and it takes paint.
• Soudal All Purpose Silicone, Charcoal. The outside job, where acrylic will not last.
• Soudal T-Rex Clear Sealant and Adhesive. Clear, so it disappears on a finished surface.
• Utility Knife with 4 Spare Blades. For cutting a seal to length and trimming back old filler.

Did you know we also stock brush door seals and automatic door seals in 915mm and 1220mm lengths, in finishes that will sit happily against most aluminium doors, and none of them are listed on the website at all. Ring us on (08) 8536 4333 with the width of your door and we will tell you what we have on the shelf.

More from DIY Insights

• How to Maintain Your Roof and Gutters to Prevent Leaks
• How to Choose Anchors and Screws for Mounting Heavy Items

I am firmly of the view that the candle test is the best ten minutes you can spend on a cold house, mostly because it finds the gap you were certain was not there.

Cheers,
Candeece