A draughty door usually comes down to two gaps: the one under the door and the ones around the edges where the door meets the frame. Seal both and you stop most of the cold air, dust and street noise a door lets through. Here is how to fit a brush bottom seal and a perimeter seal yourself, and what each one is for.
The two door gaps
Stand inside on a windy day and run your hand slowly around a closed door. You will feel air moving in two places.
The first is the gap along the bottom, between the door and the floor or threshold. It has to be there so the door can swing without dragging on the carpet or tiles, but it lets a surprising amount of air through because it runs the full width of the door.
The second is the perimeter gap, the thin space where the edge of the door sits against the frame on the hinge side, the latch side and across the top. On an older timber door these gaps are rarely even, so some spots whistle while others sit snug.
Each gap needs a different seal. The bottom takes a brush bottom seal that sweeps the floor as the door closes. The perimeter takes a compressible seal that the door presses against when it shuts. If you want the background on where draughts come from and why sealing makes a difference, we cover it in what is draught proofing.
Fit a brush bottom seal
A brush bottom door seal is an aluminium carrier with a dense brush pile that screws to the bottom of the door face. The brush drops into the floor gap and drags lightly across the floor as the door moves.
You will need a tape measure, a hacksaw, a drill, a screwdriver and a pencil.
- Measure the width of the door and cut the carrier to length with a hacksaw. Take a little off each end rather than everything off one end, so the brush stays centred.
- Close the door and hold the seal against the inside face at the bottom, with the brush just touching the floor. On carpet, let the brush press in slightly. On tiles or timber, set it so the brush kisses the surface without dragging hard, or the door will be stiff to open.
- Mark the screw holes with a pencil, then open the door and drill small pilot holes so the timber does not split.
- Screw the carrier on loosely first. Most carriers have slotted holes so you can nudge the height up or down before you tighten. Close the door, check the brush is doing its job along the whole width, then tighten fully.
Open and close the door a few times. The brush should sweep the floor with light, even contact and no hard spots. If one end drags and the other floats, the carrier is not level, so loosen the screws and adjust the height in the slots.
Fit a perimeter seal
A PVC perimeter seal handles the edges. It fixes to the frame, not the door, so the door closes against it and squashes it into the gap.
- Clean the frame where the door shuts against it. The seal beds down better on a clean, dry surface.
- Start at the top of the frame. Hold the seal in the rebate, the step in the frame that the door closes into, so the door will just compress it when shut.
- Work down each side. Cut the ends square where the top piece meets the side pieces so there are no gaps left at the corners.
- Close the door and check it still latches without a hard shove. If it is too tight, the seal is sitting too far into the gap. Ease it back a touch until the door shuts firmly but not with a fight.
A perimeter seal that is set right gives a soft, even resistance as the door closes, and the whistling around the edges stops. Check the hinge side as well as the latch side, because that is the edge people forget and it draughts just as much.
Wooden door kits
Buying the brush bottom and the perimeter seal together is simpler than sourcing them separately, and it means the two parts are matched to seal a whole door in one go.
The Single Wooden Door Draught Seal Kit (Standard) covers one external timber door with a brush bottom and a perimeter seal. The Single Wooden Door Draught Seal Kit (Premium) is the same idea with an upgraded seal for doors that cop a lot of weather or a lot of daily use.
Both are DIY jobs with a screwdriver and an hour or so of your time. Measure your door width first so you know the carrier will cover it, and check whether the door opens in or out, because the brush seal goes on the inside face either way.
How to check your work
Once both seals are on, close the door and go back to the hand test on a windy day. The bottom and the edges should feel still where they were moving air before. A stick of incense or a candle held near the gap is an easy way to see it: the smoke or flame that used to lean now sits straight. If one spot still leaks, it is almost always a seal set slightly too high or too shallow, and a small adjustment fixes it.
FAQ
Which gap should I seal first?
Do the bottom first. It is usually the biggest single gap and the easiest to feel a difference from. Then fit the perimeter seal to catch the edges.
Will a brush bottom seal drag on my carpet?
A brush seal is made to sweep across carpet with light contact. Set the height so the brush just touches when the door is closed. If it drags hard and the door is stiff, raise the carrier slightly using the slotted screw holes.
Can I fit these to any door?
Brush bottom and perimeter seals suit standard hinged timber doors. Very warped or badly fitting doors may need easing or planing first so the seals sit evenly. Sliding and bifold doors need a different product.
Do I seal the front and back doors the same way?
Yes, the method is the same for any external hinged door. Fit the brush bottom to the inside face so it stays out of the weather, and run the perimeter seal around the frame.