1. Check whether this is a suitable DIY job
A loose seal on an ordinary external door may be a straightforward maintenance task. Fire doors, smoke-control doors, communal entrances and doors with specialist security or accessibility requirements are different. Their seals, clearances and closing mechanisms form part of a designed system. Ask a competent specialist before altering them.
Never cover a ventilation grille, air brick, trickle vent or combustion-air opening to stop a draught. Some rooms and appliances depend on permanent ventilation. If you are unsure why an opening exists, establish its purpose first. Draught-proofing should not reduce the safe operation of heating appliances or emergency exits.
2. Locate the actual air path
On a breezy day, move a thin strip of tissue around the closed door’s perimeter, keeping fingers clear of pinch points. Look for movement near the latch, hinge side, head, threshold and letter opening. Do not use a candle, lighter or smoke source to trace leaks.
Check for daylight and inspect the existing seal for flattened, torn or missing sections. A paper strip gently trapped in the closed door can help compare contact around the frame, but it is not a calibrated measurement. Water staining, rotten timber or a visibly distorted frame indicates a repair problem rather than simply a missing strip.
3. Compare seal types by function
Self-adhesive foam is easy to cut and useful for suitable small gaps, but repeated compression and poor surface preparation can shorten its life. Profiled rubber or similar resilient seals can accommodate a defined gap range and often recover their shape better. Match the profile to the door manufacturer’s specification where available.
Brush strips suit some threshold and sliding applications but do not provide the same compression seal as a compatible bulb profile. A bottom sweep can reduce an under-door draught, yet may drag on an uneven floor. Exterior thresholds also manage rainwater: an improvised sweep must not obstruct drainage or redirect water indoors.
4. Measure and prepare the contact surface
Measure the perimeter sections separately and record how the gap changes. Use the seal supplier’s gap-measuring method and choose a product whose stated working range matches the closed clearance. A seal that fills the open gap completely may be much too thick once compressed.
Remove a failed adhesive strip gently. Clean residual adhesive with a method compatible with the frame finish, then let the surface dry. Repair loose paint before applying a new strip. Check the installation temperature and curing guidance for the adhesive. A cold, dusty or damp frame can undermine a correctly selected seal.
5. Fit without stretching
Dry-position a short section and close the door carefully to check that the latch still engages normally. Apply the strip in its intended location, removing backing progressively and pressing firmly as directed. Do not stretch it around the frame; it may later contract and leave gaps at the corners.
Make neat joints according to the profile instructions. Do not overlap material into a bulky corner or stack new seals over old ones. Screw-fixed products require suitable fixings and knowledge of the frame construction. Do not drill into an unfamiliar metal or composite frame without manufacturer guidance.
6. Test the whole door, not just the draught
Open, close, latch and lock the door several times from both sides. It should operate without slamming or excessive force. Check that the seal has not folded into hinges or obstructed hardware. If closure is difficult, revisit the seal size and placement instead of adjusting the latch to crush an oversized strip.
Repeat the tissue check and inspect after a few days of use. Keep seals clean using their recommended cleaning method and replace damaged sections when needed. If condensation increases, review ventilation rather than assuming a tighter room is always better. Actual comfort and energy effects depend on the building; no universal saving can be promised.