Fix It Britain

Learning how to draught-proof doors and windows is one of the cheapest, quickest ways to make a UK home feel warmer this winter. Most draughts come through a handful of obvious gaps – around opening casements, under the front door, through the letterbox and keyhole – and nearly all of them can be sealed in an afternoon with a few basic products. Here’s how to find the leaks, pick the right seal and fit it so everything still closes properly.

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At a glance

• Difficulty: Easy – a confident beginner can do all of it
• Time needed: 20–40 minutes per window or door; a half-day to a full day for a typical house
• Best time to do it: Early autumn, on a dry day – self-adhesive strips stick best to clean, dry, room-temperature surfaces
• Best for: Older timber casement and sash windows, front and back doors, letterboxes, keyholes and loft hatches

Why draught-proofing is worth doing

Every gap that lets cold air in also lets warm air out, so your heating works harder for a house that never quite feels cosy. The Energy Saving Trust says draught-proofing windows and doors brings a worthwhile yearly saving in a typical gas-heated semi-detached home, and that a draught-free home feels warmer at a lower temperature, so you may be able to turn the thermostat down by a degree or two.

There is one important rule: draught-proofing is not the same as stopping ventilation. You want to block the accidental gaps, not the deliberate ones. The government’s Existing Home Ventilation Guide says Building Regulations require that ventilation in your home is not made worse by energy-efficiency work, and advises keeping trickle vents open and unblocked, even in winter.

Know what you’ve got: choosing the right seal

The most common mistake is buying one roll of strip and using it everywhere. Gaps vary from almost nothing on a modern uPVC casement to several millimetres on an old timber door, so measure first and match the product to the gap. The Energy Saving Trust puts it simply: if the strip is too big it gets crushed and the window may not close; too small and it leaves a gap.

• Self-adhesive foam strip: cheap and easy, but it flattens and wears out quickly. Fine for a loft hatch or a window you rarely open.
• E-profile rubber (EPDM) strip: for small, even gaps. Stormguard’s E-profile is sold for gaps of 1.5–3mm.
• P-profile rubber (EPDM) strip: the most popular all-rounder for timber casements and doors. Stormguard’s P-profile is listed for gaps of 3–5mm.
• Pin-on or screw-fix brush and wiper strips: plastic or aluminium carriers with a brush or flexible blade. Longer-lasting, and better for larger or uneven gaps, external doors and sashes.
• Door-bottom brushes and flaps: close the gap above the floor or threshold; brushes cope well with uneven floors.
• Letterbox brushes or flaps and keyhole covers: quick fixes for two big draught sources on a British front door.
• Clear or colour-matched silicone: for windows that never open and for gaps between a window frame and the wall.

A note on uPVC. Modern uPVC and composite doors and windows have rubber gaskets built in, so don’t stick foam over them. Check whether the gasket has shrunk, split or popped out of its groove (replacement gasket is available by the metre), and whether the door needs adjusting – many uPVC doors have adjustable keeps or cams on the frame that pull the door tighter against the seal.

Sash windows and listed homes. Traditional sliding sashes need a gap to move, so stiff rubber strips can make them jam. The Energy Saving Trust recommends brush strips or a professional for sashes. If your home is listed, Bath & North East Somerset Council’s guidance notes that listed building consent is not normally needed for discreet draught-proofing, but check with your own council’s conservation officer before fitting anything visible.

Before you start: rooms to be careful with

Some rooms need a steady supply of fresh air. Dorset Council’s draught-busting manual warns that rooms with a gas fire, solid fuel fire or an open-flued boiler need adequate ventilation, and that it may be better not to draught-proof them at all to avoid a build-up of carbon monoxide. If you have one of these appliances, leave its room’s ventilation as it is, make sure you have a working carbon monoxide alarm, and ask a Gas Safe registered engineer for advice before sealing anything. Kitchens and bathrooms also need good ventilation to keep condensation and mould under control.

What you’ll need

• Self-adhesive rubber draught excluder strip (E- or P-profile to suit your gaps)
• A door-bottom brush strip or flap draught excluder
• A letterbox brush or flap, and a keyhole cover (escutcheon with a drop-down disc)
• Steel tape measure and a pencil
• Sharp scissors or a utility knife, and a junior hacksaw for cutting aluminium carriers
• Cordless drill/driver or screwdriver, plus a bradawl
• Cleaning cloths, sugar soap or warm soapy water, and white spirit or isopropyl alcohol to degrease
• Clear or white silicone sealant and a sealant gun (for fixed windows and frame gaps)

Step 1: Find the draughts

On a cold, breezy day, slowly move the back of your hand around each door and window, the letterbox, keyhole, cat flap and loft hatch. Dorset Council also suggests checking between the window frame and the wall, and, on older windows, anywhere the putty has shrunk or fallen out. An incense stick or a strip of tissue held near the gap makes small leaks easier to see: if the smoke or tissue flutters, you’ve found one.

Step 2: Measure the gaps

For each opening window or door, you need two measurements: the total length of strip (add up all four sides of the frame, plus about 10% for waste) and the size of the gap itself. A handy trick for the gap: press a small ball of modelling clay or Blu Tack onto the frame rebate wrapped in cling film, close the window or door gently, then open it and measure how thick the squashed clay is. That thickness is your gap.

Gaps are rarely even – old doors often fit tighter at the hinge side – so measure in a few places. If gaps vary a lot, a brush strip is more forgiving than rubber.

Step 3: Clean and prepare the frames

Self-adhesive strips fail for one main reason: they’re stuck onto dust, grease or flaking paint. Wash the rebate where the strip will go with sugar soap or warm soapy water, rinse, and let it dry completely. Then wipe with white spirit or isopropyl alcohol, and scrape off any loose paint – the strip is only as secure as the surface beneath it.

If you’ve recently painted, wait until the paint has fully hardened (check the tin – many paints cure long after they feel touch-dry). Adhesive grips poorly in the cold, so warm the room first if the frame is chilly.

Step 4: Fit self-adhesive strip to opening windows

Stick the strip to the frame, not the opening part of the window, on the face that the window closes against. Start at a top corner and work along, peeling off the backing a little at a time rather than all at once so it doesn’t stick to itself. Press firmly along its length without stretching it – stretched rubber shrinks back later and leaves gaps at the corners.

At the corners, cut the strip rather than bending it round, and butt the two ends neatly together. On a casement’s hinge side the seal is squeezed hard, so a thinner E-profile often works better there. When you’re done, close the window and check it latches without forcing. You should feel slight resistance, but the handle shouldn’t need muscle.

Step 5: Seal the edges of external doors

Doors take more abuse than windows, so a longer-lasting product pays off here. For timber doors you can use the same P-profile rubber strip in the door stop rebate, or a pin-on or screw-fix brush/wiper strip on the frame. Dorset Council’s manual recommends fitting with the door shut and locked, doing the top strip first and then the sides, and nailing each fixing only halfway at first so you can adjust the position before driving it home. Aim for the seal to press lightly against the door – about 3mm of compression – so you can see it move when the door opens and closes.

If you now have to lean on the door to lock it, the seal is too thick and will strain the lock.

Step 6: Fit a brush strip to the bottom of the door

The gap under an external door is often the worst draught in the house. Measure the width of the door and cut the strip to length – aluminium carriers cut easily with a junior hacksaw, then trim the brush with scissors. Hold it against the inside face of the door with the bristles just touching the floor or threshold, mark the screw holes with a bradawl, and screw it on.

The bristles should lightly brush the floor, not bend flat – too low and the door drags; too high and you’ve gained nothing. For gaps up to about 15mm over tiles or uneven floors, Dorset Council’s guide suggests a self-adhesive brush; for carpet, a screw-fixed brush is sturdier. Internal doors only need this if they open onto an unheated room, such as a garage or a porch.

Step 7: Tackle the letterbox and keyhole

An internal brush letterbox cover screws over the inside of the opening and closes it with two rows of bristles. Measure the inside opening before you buy, and once it’s fitted, push a magazine through to check post still goes in easily and doesn’t snag. For the keyhole, fit a cover with a swinging metal disc.

Step 8: Seal fixed windows and frame gaps

Windows that never open can be sealed with silicone, as the Energy Saving Trust suggests. The same goes for any small gaps between the window frame and the wall inside: rake out any loose old filler, clean and dry the joint, then run a neat bead of decorator’s caulk (if you’ll paint over it) or silicone (if you won’t). Large gaps around the outside of a frame need a window fitter.

Step 9: Check your work

On the next breezy day, repeat the hand or tissue test from Step 1. Close each window and door and slide a sheet of paper into the closed gap at several points: if it pulls out with no resistance, that spot still isn’t sealing. Windows that need force to lock, sticking sashes or dragging doors mean a seal is too thick – swap it now before it damages a hinge or lock.

Common mistakes to avoid

• Blocking trickle vents, air bricks or extractor fans. These are deliberate ventilation – sealing them leads to condensation, mould and stale air.
• Draught-proofing a room with an open-flued gas boiler, gas fire or wood burner. These appliances need air; get advice from a Gas Safe engineer or HETAS-registered installer first.
• Using a strip that’s too thick. Windows that won’t latch put strain on hinges and handles, and you’ll end up pulling the strip off.
• Sticking strip onto dirty or damp frames. It will peel off within weeks – clean and degrease first.
• Stretching rubber strip as you apply it. It shrinks back and opens up gaps at the corners.
• Covering uPVC gaskets with foam. Replace or reseat the built-in seal, or adjust the door, instead.

When to call a professional

Call a window and door repairer if a uPVC unit still leaks after you’ve checked the gaskets and adjustment, or if a lock or hinge is faulty. Rattling, sticking or rotten sash windows are best overhauled by a sash specialist, who can rout discreet seals into the joinery. Unsure about ventilation for a gas or solid fuel appliance? Ask a Gas Safe registered engineer or a HETAS-registered installer. And if you’re replacing windows, Building Regulations apply, so use a FENSA- or CERTASS-registered installer who can certify the work.

Frequently asked questions

Is it worth draught-proofing double-glazed windows?

Usually the leak is the seal around the opening sash, not the glass. Check the rubber gasket in the frame for splits or gaps and see whether the window needs adjusting so it closes tightly. Replacing a worn gasket is usually better than adding stick-on strip.

Can draught-proofing cause condensation or damp?

It can if you overdo it and block ventilation, because moist air has fewer ways to escape. Keep trickle vents open, use extractor fans when cooking and showering, and open windows briefly each day. Sealing accidental gaps around doors and windows while keeping deliberate ventilation working is the right balance.

How long does self-adhesive draught strip last?

Foam strip is the shortest-lived and may only last a season or two on a window you open often. Rubber (EPDM) P- and E-profile strips last considerably longer, and screw-fix brush or wiper strips longer still. Replace any strip that has flattened, cracked or started peeling away.

What’s the best draught excluder for under a door?

For most front and back doors, a screw-fixed brush strip on the inside face is the most reliable, because it copes with uneven floors and is easy to adjust. A hinged flap works well where there’s a threshold, and a fabric “sausage” draught excluder is a handy no-tools option for internal doors.

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