As temperatures dip and budgets strain, a near-forgotten method from the 1920s is back in the toolkit. It targets the most overlooked opening in the house: the sliver of daylight under the front door.
Why that tiny gap costs you real money
That narrow strip under a door behaves like a permanent vent. Draughts pull warm air out and drag cold air in. Radiators then run longer to hold the same room temperature. In older homes, stopping under-door leakage can shave a noticeable chunk off space-heating demand.
Seal a 5 mm gap under an 82 cm door and you close an opening roughly the size of a credit card.
Households in draughty properties report savings of up to 20% once the worst gaps are sealed. Many homes see 5–12% as a realistic range. That can mean £60–£200 a year depending on usage and tariff. The comfort change is immediate. Floors feel warmer. Rooms stabilise faster. The heating cycles less.
The throwback fix: a rubber sweep you can make in 30 minutes
This is a rigid strip mounted on the inside of the door, with a flexible skirt that kisses the floor. It stops wind without snagging on the threshold. The old-school twist uses tough rubber or thick leather, held straight by simple wire staples.
What you need
- Rubber strip about 13 mm thick and as wide as your door (bicycle inner tube or EPDM work well)
- Galvanised wire, roughly 12 gauge, about 50 cm to form two stiff staples
- Wood screws, 32 mm length, 6 to 8 pieces for secure fixing
- Alternative skirt: heavy leather, at least 2 mm thick, if rubber is not available
Pick a rubber that flexes enough to follow the floor but resists tearing. A lightly textured surface grips the air and seals better.
Step-by-step
Most beginners finish in 25–35 minutes with basic tools. A second pair of hands helps with alignment.
Pro tips from old hands
If you can hear a faint hiss as the door moves, it’s leaking. Silence means a clean seal.
- Uneven floors: angle the wire staples slightly to vary pressure where the floor dips or rises.
- Avoid warping: do not crank the screws down hard. Overtightening can bow timber and create new gaps.
- Hard floors vs carpet: keep the 2 mm clearance on hard floors. On carpet, raise it slightly to prevent drag.
- Make it last: wipe the rubber every two months with a damp cloth to remove grit that erodes the edge.
What difference will you notice
Cold eddies stop flowing along the floor. Rooms hold temperature between boiler cycles. The thermostat calls for heat less often. In windy weather the benefit scales up, because pressure differences across the door increase leakage.
Service life for a well-fitted rubber or leather skirt runs three to four winters in a typical hallway. Replacement takes minutes because the screw holes are already in place.
Numbers that help you decide
Here is an indicative snapshot for a typical gas-heated household. Your figures will vary with property age and exposure.
| Measure | Typical outcome |
|---|---|
| Under-door gap at start | 3–7 mm over 80–90 cm width |
| Equivalent open area | 24–63 cm² (matchbox to credit-card size) |
| Heating energy cut | 5–12% for many homes; up to 20% in very leaky cases |
| Annual bill saving | £60–£200 at typical tariffs and usage |
| Time to fit | 25–35 minutes with basic tools |
| Durability | 3–4 years with light cleaning |
Safety, durability and alternatives
- Check for pipes or cables near thresholds before drilling. Use short screws if the timber is thin.
- Wear gloves when shaping wire and cutting rubber. Fresh cuts in EPDM can be sharp.
- Period homes and listed doors may need reversible fittings. Use existing holes where you can.
- No wire to hand? A slim timber batten can keep the rubber straight, though it adds thickness.
- Can’t source rubber? Thick leather works well and looks smart on timber doors.
- Shop-bought alternatives include brush strips and clip-on sweeps. They install fast but may not seal uneven floors as tightly.
When the quick fix isn’t enough
Other small gaps that waste heat
- Letterboxes: fit a brush-lined cover that shuts fully after the post lands.
- Keyholes: add a simple escutcheon cover that swings shut from the inside.
- Door frames: compressible foam or EPDM seals reduce side and top leaks.
- Floorboards: flexible filler stops air rising through gaps in suspended floors.
- Unused fireplaces: an inflatable chimney blocker prevents a constant updraft.
- Loft hatches: a foam strip and tight latch stop warm air escaping upward.
A quick back-of-the-envelope example
Say your household uses 15,000 kWh of gas a year for heating. At 7 p/kWh that’s £1,050. Cut space-heating by 10% with targeted draught-proofing and you keep roughly £105 in your pocket. Add a letterbox brush and a frame seal, and the total can climb. The comfort gain often matters more than the pounds, because rooms stop feeling “gusty” near the hallway.
What to watch as the seasons change
Doors swell and shrink with humidity. Re-check the clearance after heavy rain and during dry cold spells. If the sweep starts dragging, back off the screws by a half turn or raise the strip by a millimetre. If a pet uses the door area, choose tougher rubber and clean more often to remove grit that chews the edge.
Making the fix part of a wider plan
Combine this skirt with smart controls for steadier savings. Lower the thermostat by 1°C once draughts are tamed; most people find it comfortable because the air no longer nips at the ankles. Schedule shorter boiler runs in the night once the hallway stops leaking heat. Small measures stack, and this one costs next to nothing if you upcycle materials from a shed.
