--- title: "How to draught-proof a door: the gap underneath, the edges, letterbox and keyhole (UK)" description: "The four places an outside door lets cold air in, which seal or excluder suits each gap, and what to leave alone so the house can still breathe." url: https://homecomfortlab.co.uk/heating/how-to-draught-proof-a-door/ --- # How to draught-proof a front or back door The four places an outside door lets cold air in, which seal or excluder suits each gap, and what to leave alone so the house can still breathe. By [Pete Harvey](https://homecomfortlab.co.uk/about/), editor. Updated 24 October 2026. This page links to Amazon. As an Amazon Associate I earn from qualifying purchases. [More about how this site is paid for](https://homecomfortlab.co.uk/affiliate-disclosure/). > **The short answer** > > An outside door lets cold air in at four places: the gap underneath, the edges where it meets the frame, the letterbox and the keyhole. Fit a brush or seal along the bottom, a strip around the frame, a brush behind the letterbox and a cover over the keyhole. Leave the doors between rooms alone, because air needs to move around the house. ## Find where the air gets in With the hall light off, look for light from outside showing round the edges of the door. Then, on a windy day, try these: - Run the back of a damp hand slowly round the frame, along the bottom, and past the letterbox and keyhole. - Close the door on a strip of paper at a few points along each edge. If the paper slides out easily, the door isn't pressing against anything there. - Listen for whistling, and watch for a curtain or coat on a hook moving when the wind gusts. To size a strip for the edges, wrap a small ball of Blu-Tack or modelling clay in cling film, press it onto the frame where the door closes, and shut the door gently. Open it again and measure how thin the ball was squashed. That's the gap the seal has to fill. Check a few places, because old doors are rarely the same all the way round. ## The gap under the door This is usually the biggest gap. Which fix suits depends on the door and the floor: - **A brush strip** screwed along the bottom of the door on the inside. The bristles bend over an uneven floor, a threshold or the edge of a mat, so it suits most front and back doors. - **A weatherbar** on the outside face of a door that catches the rain. It throws water clear of the threshold, and many have a brush or rubber seal underneath as well. - **A slide-on excluder**, two foam tubes joined by fabric that sit either side of the door. No tools or screws, so it suits renters, though on an outside door it wears where it drags on the mat. - **A fabric "sausage"** laid along the bottom. It works, but you have to put it back each time the door opens. Fine as a stopgap. Measure the door's width and the gap under it at both ends before you buy. Brush strips can be cut to length with a hacksaw. ## The edges of the door On a wooden door, the cold air comes through the gap between the door and the frame stop, the strip of wood it closes against. A self-adhesive strip stuck to the stop fills it. The Energy Saving Trust lists two kinds: foam strips, which are cheap and easy but don't last long, and brush or rubber "wiper" strips, which last longer. - Choose a strip made for the gap you measured. Too thick and the door won't latch, which strains the lock; too thin and air still gets through. - Clean the frame with soapy water and let it dry before you stick anything on. Adhesive won't hold on dust or old polish. - Fit the hinge side as well as the latch side and the top. The hinge side is easy to forget. > **uPVC and composite doors** > > Most modern uPVC and composite doors already have rubber seals in the frame. If one is draughty, the seal may be squashed flat or the door may have dropped on its hinges. Many of these doors have adjustable hinges and keeps (the plates the locking bolts go into), so a locksmith or door fitter can often adjust it to close tighter, or fit a new seal. Sticking foam over the old seal can stop the door locking properly. ## The letterbox and keyhole A letterbox with only an outside flap lets the wind straight through. A brush plate screwed over the opening on the inside stops most of it while still letting post in. Measure the opening, not the outside plate, and check the screw holes won't land on the glass or the lock. An old-style keyhole is a small hole, but it lets in a steady stream of air. A keyhole cover has a small metal disc that swings down over the hole when there's no key in it. ## What to leave alone - **Doors between rooms.** The Energy Saving Trust says inside doors shouldn't be draught-proofed: the gap underneath lets air move through the house, which carries moisture away. - **Kitchen and bathroom doors** most of all, because that's where the moisture is made. Sealing them pushes the damp into one room, where it ends up on the walls. See [black mould on walls](https://homecomfortlab.co.uk/mould/get-rid-of-black-mould-on-walls/). - **Any vent a gas fire, boiler or open fire needs** to burn safely. If a room has one, don't seal it until you know where its air comes from; a Gas Safe registered engineer can tell you. - **Trickle vents** in the door or window frames. Leave them open. ## What it saves The Energy Saving Trust estimates that draught-proofing the windows, doors and floors of a home in Great Britain saves about £55 a year (about £80 in Northern Ireland). The bigger gain is often comfort: a hallway without a cold draught feels warmer at the same thermostat setting, so you may be able to turn it down. The Trust puts the saving from turning the thermostat down from 22°C to 21°C at about £120 a year. [Heating cost per hour](https://homecomfortlab.co.uk/tools/heating-cost-per-hour/): Compare what an hour of heating costs with gas, oil, a heat pump or a plug-in heater. ## Our picks Chosen by what each product does against the gaps above, from the makers' specs. We haven't tested them ourselves. ### For the gap under most outside doors Stormguard Aluminium Brush Bottom Door Seal (838mm) - **Type:** Door brush strip - **Size:** 838mm, cut to fit - **Seals gaps:** up to 25mm A brush in an aluminium carrier that screws along the bottom of the door and seals gaps up to 25mm, so it copes with most uneven floors and thresholds. It's 838mm, cut to fit; Stormguard makes longer ones for wider doors. [View on Amazon](https://homecomfortlab.co.uk/go/dx-door-brush-a/) [Manufacturer specs](https://www.stormguard.co.uk/stormguard-products/aluminium-brush-bottom-door-seal/) ### For a door that catches the rain Stormguard XRD Rain Deflector with rubber seal (914mm) - **Type:** Weatherbar - **Size:** 914mm, cut to fit An aluminium weatherbar with a rubber seal underneath, screwed to the outside face of the door. Stormguard says it suits doors that open inwards or outwards. It's 914mm, cut to fit. [View on Amazon](https://homecomfortlab.co.uk/go/dx-weatherbar-a/) [Manufacturer specs](https://www.stormguard.co.uk/stormguard-products/xrd-rain-deflector/) ### For the edges of a wooden door tesa INSULATION Rubber Weatherstrip S (E-profile) - **Type:** Seal strip - **Size:** 6m - **Seals gaps:** 1 to 3.5mm - **Lasts:** up to 8 years A self-adhesive rubber strip for gaps of 1 to 3.5mm, which tesa rates to last up to 8 years, far longer than foam. If your Blu-Tack test showed a wider gap, tesa's [size L (Amazon)](https://homecomfortlab.co.uk/go/dx-door-seal-b/) covers 2 to 5mm. tesa says it may leave adhesive behind when you take it off, so ask first if you rent. [View on Amazon](https://homecomfortlab.co.uk/go/dx-door-seal-a/) [Manufacturer specs](https://www.tesa.com/en-gb/consumer/tesa-insulation-rubber-weatherstrip-small.html) ### For the letterbox Stormguard PVC Brush Letterplate - **Type:** Letterbox brush - **Size:** 335 x 75mm, for openings up to 279 x 45mm Twin brushes on the inside of the letterbox stop the wind blowing straight through. It covers openings up to the size in its specs, so measure yours first. [View on Amazon](https://homecomfortlab.co.uk/go/dx-letter-a/) [Manufacturer specs](https://www.stormguard.co.uk/stormguard-products/pvc-brush-letterplate-no-flap/) ### For the keyhole Stormguard Key Hole Cover (chrome effect) - **Type:** Keyhole cover Stormguard makes this cover for the keyholes of traditional mortice locks, to cut draughts and rain coming through. Check it's the right size for your keyhole before you order. [View on Amazon](https://homecomfortlab.co.uk/go/dx-keyhole-a/) [Manufacturer specs](https://www.stormguard.co.uk/stormguard-products/key-hole-cover-2/) ### No tools, or if you rent Everlasting Comfort Twin Under-Door Draught Excluder - **Type:** Door excluder - **Size:** Fits doors 76 to 91cm wide Slides onto the bottom of the door with a foam tube either side, so there's nothing to screw in or stick on. Check the width suits your door. [View on Amazon](https://homecomfortlab.co.uk/go/dx-door-a/) For windows, see [draught excluders and window film](https://homecomfortlab.co.uk/heating/draught-excluders-and-window-film/). For a front door that opens into the living room, a heavy curtain on a rising rod helps too: see [do thermal curtains work?](https://homecomfortlab.co.uk/heating/do-thermal-curtains-work/) ## Sources - [Energy Saving Trust: draught proofing](https://energysavingtrust.org.uk/advice/draught-proofing/) Checked 24 October 2026. ## Read next - [Draught excluders and window insulation film](https://homecomfortlab.co.uk/heating/draught-excluders-and-window-film/) (Buying guide) Cheap draught proofing that makes a real difference: door excluders, letterbox brushes and window film. - [Do thermal curtains work?](https://homecomfortlab.co.uk/heating/do-thermal-curtains-work/) (How to) Heavy lined curtains cut the heat lost through a window at night, most of all on single glazing. What the tests show, how to hang them so they work, and when a lining is enough. - [Heating cost per hour: throw, heaters, gas, oil and heat pump compared](https://homecomfortlab.co.uk/tools/heating-cost-per-hour/) (Calculator) Compare the hourly cost of a heated throw, electric blanket, plug-in heaters, and gas, oil, heat pump and electric central heating. - [Heated airer running costs](https://homecomfortlab.co.uk/heating/heated-airer-running-costs/) (Running costs) What heated clothes airers cost per hour and per load at the current price cap, and how that compares with a tumble dryer. --- As an Amazon Associate I earn from qualifying purchases. Links to shops are marked, and earning from them never decides what we recommend. [How this site is paid for](https://homecomfortlab.co.uk/affiliate-disclosure/). Running costs use 26.32p per kWh for electricity and 7.97p per kWh for gas, the [Ofgem price cap, Direct Debit average for England, Scotland and Wales](https://ofgem.gov.uk/news/changes-energy-price-cap-between-1-october-and-31-december-2026) for 1 October to 31 December 2026.