Draught-proofing floors, loft hatches and other gaps

Once the doors, windows and chimneys are sealed, the draughts that remain usually come from less obvious places: gaps between floorboards, the join between the floor and the skirting, the loft hatch, and holes made over the years for pipes and cables. Each one is small, but together they add up to a draught you can feel.

Most of these jobs take an hour or two and cost very little.

What it saves

The Energy Saving Trust estimates that draught-proofing windows, doors and floors together saves a typical home in Great Britain about £55 a year, or £80 in Northern Ireland. Floors are often the part people notice most, because the cold air comes in at ankle height.

Before you start

Keep air bricks clear. If your home has a suspended timber floor, the small grilles in the outside walls just above ground level let air flow under it. That airflow keeps the joists dry. Never block them, and don’t seal the floor so completely that the space underneath can’t breathe, or the timber can rot.

Turn the power off before working near electrics. Anything involving sockets, switches or light fittings needs the circuit switched off at the consumer unit. If you’re not confident, ask an electrician.

Keep foam and fillers away from heat. Don’t use expanding foam or other fillers round flues, boiler outlets or anything that gets hot.

Floors and skirting boards

Solid concrete floors rarely cause draughts. Suspended timber floors, common in older houses, often do: the boards shrink and gaps open between them, and cold air from the ventilated space underneath comes straight up.

Gaps between floorboards

Flexible gap-filler strip. A rubber or foam strip pushed into the gap with a scraper or blunt knife. Quick, almost invisible, and it moves with the boards. The easiest DIY fix.
Timber slips. Thin strips of wood glued along one side and planed flush. The traditional repair, and the best-looking one on boards you want to keep on show. Best suited to wider gaps.
Clear or matching flexible filler. For narrow gaps. Avoid hard fillers that crack as the boards move.
Rugs, carpet or underlay. If you don’t mind covering the boards, carpet on a good underlay, or hardboard sheet under it, stops most floor draughts in one go. A thick rug over the worst area helps even on its own.

Between the floor and the skirting

This gap is often bigger than any between the boards. Run a bead of decorator’s caulk or flexible sealant along it. For a wide gap, push in a foam backer rod first and seal over it. Fitting a beading strip along the foot of the skirting is another neat option.

Insulating under the floor

For the biggest improvement, insulation can go between the joists under the boards. If you have access from a cellar or crawl space it can be fitted from below; otherwise the boards need lifting, or a specialist can spray insulation from below using a small robot. Either way, the air bricks must still be able to ventilate the space underneath.

Loft hatches

A loft can be well insulated and still lose warm air through the hatch, which is often a thin board resting loosely in its frame. Warm, moist air escaping into a cold loft can also cause condensation on the roof timbers.

Seal the gap. Stick a compressible foam or rubber strip round the frame where the hatch rests, so the hatch squashes it when closed.
Hold it down. A hatch that just sits in place can lift slightly. Two turn buttons or simple catches pull it tight against the seal.
Insulate the hatch itself. Fix a piece of rigid insulation board to the top of the hatch, or wrap a piece of loft insulation in polythene and staple it on, a little smaller than the hatch so it still closes.

If the hatch is a standard size, a ready-made insulated hatch with a built-in seal and latch is a straightforward swap. Loft ladders that fold into the hatch need a seal that suits them, so check with the ladder’s maker.

Pipes, cables and holes through walls

Every pipe, cable and duct that goes through an outside wall needed a hole, and the hole is often bigger than what goes through it. Check:

under the kitchen sink and behind the washing machine, where waste and supply pipes leave the house
where the gas and water supplies come in, often under the stairs or in a utility room
round TV aerial, satellite and broadband cables
old holes from appliances that have since been removed
boxed-in pipes, where the boxing hides a gap into the floor or wall

How to fill them:

Small gaps: decorator’s caulk inside, exterior-grade sealant outside.
Larger holes: expanding foam, trimmed flush once set and then sealed or painted over. Don’t overfill, as the foam swells as it sets.
Older solid walls: use lime mortar or sheep’s wool rather than foam, so the wall can still dry out.
Unused holes: fill them completely, inside and out.

Leave alone anything that is meant to be open: air bricks, vents, overflow pipes and the flue or air supply to a boiler or gas fire.

Sockets, switches and downlights

Sockets and switches on outside walls. Air can get in through the back box and round the faceplate, especially in older homes or timber-framed walls. Foam gaskets cut to fit behind the faceplate are cheap and effective. Switch off the circuit at the consumer unit before removing a faceplate, or ask an electrician to fit them. Modern sockets in solid walls are rarely a big source of draughts, so start with the older ones.

Downlights in the ceiling below a loft. Recessed downlights need a hole in the ceiling, and warm air escapes through it into the loft. They can’t simply be covered over, because many get hot and need space round them. The safe options are:

Fire-rated downlight covers fitted over each light from the loft side, so insulation can be laid over the cover rather than the fitting. Check the cover suits your type of downlight and gives enough clearance.
Replacing old fittings with sealed, fire-rated LED downlights designed to be covered with insulation (often marked “IC” for insulation contact). This is a job for an electrician.

Never lay loft insulation directly over a downlight that isn’t designed for it.

Extractor fans. A fan that lets cold air back in when it’s off needs a backdraught shutter, a flap that closes when the fan stops. Many fans have one; if yours rattles or lets in a draught, the shutter may be stuck or missing.

Older and listed homes

Old floorboards and skirtings are part of a house’s character, so choose methods you could undo later. Flexible strips, timber slips and filler in the gaps between boards change little and are usually acceptable. Heavy sealant across the boards changes how they look and makes them harder to lift for future repairs, so avoid it on boards you want to keep on show.

If you’re planning other work that means lifting boards, such as rewiring or plumbing, do it before sealing the gaps.

On a listed building, draught-proofing floors doesn’t normally need listed building consent, unless it would noticeably change the room’s appearance. Lifting historic boards, removing skirtings or insulating under the floor may need it. Your council’s conservation officer can advise.

In older homes with solid walls, use materials that let moisture pass through, such as lime mortar or sheep’s wool, to fill holes in walls, rather than cement or foam.

If you rent

Rugs, flexible gap-filler strip and a seal round the loft hatch are usually fine without asking. Anything involving electrics, lifting boards or filling holes in walls is for your landlord to arrange or agree.

Where to buy

Floor gap fillers, seals, caulk, foam and downlight covers are sold by DIY stores and builders’ merchants. Underfloor insulation is a specialist job. Examples, in alphabetical order:

Chimney Sheep (wool strips for gaps and seals): chimneysheep.co.uk
DraughtEx (floorboard gap-filler strip): sold by B&Q and others
Q-Bot (robotic underfloor insulation for suspended timber floors): q-bot.co
Stormguard (foam and rubber seals for loft hatches): sold by most DIY stores

Chimney Sheep is the company that runs this site.

Sources

Last checked 23 October 2026.