Fit a letterbox draught excluder

Fit a letterbox draught excluder to stop cold air whistling through your front door in under an hour.

LB-01Check what kind of door you haveWork out if your door is timber, composite, or uPVC/plastic — this changes what screws you use later. Composite and uPVC doors often have a metal reinforcing box section inside the stile, so screws need to be short and self-tapping, not long wood screws. Also check whether your door is a designated fire door — common in flats, maisonettes and communal entrances, usually marked with a coloured disc or label on the top edge.

RULES

KNOW THE RULES

If your front door is a fire door (common in flats and shared buildings), any letterbox fitting must keep its fire performance. Use a letterbox excluder with an intumescent seal rated for fire doors, and don't drill extra holes beyond what the manufacturer specifies. If you're unsure, ask your landlord, managing agent, or building control before changing a fire door.

LB-02Measure the letterbox apertureMeasure the width and height of the existing hole cut in the door, in mm. Standard UK letterbox apertures are usually 40mm x 250mm or 40mm x 300mm, but older doors can vary. Take your new draught excluder's spec sheet and check its plate size covers your aperture with at least 10mm of overlap all round.

1 each · Tape measure

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LB-03Remove the old letterbox plateUnscrew and lift away the existing letterbox flap or plate from both sides of the door. Keep the old screws to one side in case the new kit doesn't include the right length. Wipe down the aperture edges with a damp cloth to clear dust and old paint flakes.

1 each · Screwdriver (flathead and Phillips set)

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1 each · Cloth

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LB-04Offer up the new draught excluder and mark the holesHold the new excluder plate over the aperture from the outside, centred over the hole, and mark the screw positions through the fixing holes with a pencil. Check it sits flush and square before marking. On uPVC or composite doors, avoid marking holes near the edge of the stile where the internal lock mechanism runs — usually within 150mm of the handle or lock cylinder.

1 each · Pencil

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LB-05Drill pilot holes to suit your doorOn a timber door, drill a 2mm pilot hole at each marked point to stop the wood splitting when you drive the screw. On a uPVC or composite door, most excluder kits are designed for self-tapping screws that don't need a pilot hole — check the instructions first, as drilling an oversized hole here will make the fixing loose. Never drill deeper than the door thickness, and stop immediately if you feel the drill bite into something solid and metallic that isn't the reinforcing plate — this could be the multi-point lock mechanism.

1 each · Cordless drill

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1 each · 2mm drill bit

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LB-06Fit the excluder and secure both platesHold the outer plate in place and fit the inner plate from the other side of the door, sandwiching the letterbox aperture between them. Drive in the screws provided, tightening evenly on each corner rather than fully tightening one side first. Don't overtighten on composite or uPVC doors — the plastic skin can crack if you force it.

1 each · Letterbox draught excluder kit (brush or flap type)

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LB-07Test the letterbox works properlyPush a few envelopes and a folded newspaper through from the outside to check the flap or brush strip doesn't snag or block post. Open and close the flap a few times to make sure it isn't rubbing on the door or frame. Check from inside that daylight and draught are properly blocked around the edges.

LB-08Tidy upSweep or vacuum up any drill dust or paint flakes from the doorstep and hallway floor. Dispose of the old letterbox plate and screws, or keep them if you might need a spare fixing later. Give the new excluder a wipe to remove fingerprints and pencil marks.

1 each · Handheld vacuum or dustpan and brush

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