Draught Proofing: Measure the Gap, Not the Door

Draught proofing is one of the cheapest improvements a house can have and it is done badly more often than not. The two failure modes are the wrong thickness and a surface that was not properly prepared.

Measure the gap

Close the door on a piece of paper and pull. If it slides out easily there is a gap; if it tears there is not. Do this at several points — gaps are rarely even.

For a proper measurement, use a coin or a drill bit as a gauge, or slide a folded strip of card into the gap and mark where it stops.

Seal is sold by width and thickness. Thickness has to be slightly greater than the gap so it compresses; too much thicker and the door will not close, which is a worse outcome than the draught.

Types of seal and where each belongs

E, P and D profiles are rubber and are named for their cross-section. E is for gaps of 2 to 3.5 mm, P for 3 to 5 mm, D for 3 to 7 mm. Rubber lasts far longer than foam.

Foam strip is cheap, easy and compresses permanently within a season or two. Fine for a window that is never opened; poor for a door in daily use.

Brush strip suits sliding doors and the bottom of doors over carpet, where a compression seal would bind.

A door threshold or draught excluder handles the bottom gap, which is usually the largest and the most neglected.

Preparing the surface — the step that gets skipped

Self-adhesive seal fails because it was stuck to dust, gloss paint residue or a cold damp frame.

Clean the frame with sugar soap or a degreaser, rinse, and let it dry completely. Do not fit below about 10°C — the adhesive will not bond and will let go within weeks.

Fit in one continuous run per side rather than joining short pieces, and press firmly along the whole length. Give it 24 hours before slamming the door.

Where to seal and where not to

Seal: door and window frames, the loft hatch, letterboxes, keyholes on external doors, and the gaps around pipes entering the house.

Do not seal: air bricks, extractor vents, trickle vents in window frames, or any purpose-provided ventilation. Rooms with a fuel-burning appliance need their ventilation and blocking it is dangerous.

Bathrooms and kitchens need to be able to lose moisture. Sealing them fully without adequate extraction produces condensation and mould.

Order of value

Loft hatch first — it is often the biggest single hole in a house and the cheapest to fix. Then external doors, then the bottom of internal doors to unheated rooms, then windows.

The chimney, if you have an unused one, is worth a proper chimney balloon.

Checking your work

On a windy day, run the back of a damp hand slowly around each frame. Moving air is much easier to feel on damp skin. A lit incense stick shows air movement visually.

What we stock

Seal is listed by profile, width and thickness in Air, Seal and Comfort. Measure the gap first and the choice becomes obvious.

All articles

Browse the full range in the shop, read the frequently asked questions, or contact us — Homemaker Plus, Belton, MO.