How do I stop draughts around my front door?

What this usually means

A front door has to be a moving part, so it is built with gaps — a clearance at the threshold to let it swing, margins down the hinge and closing sides and across the top, and openings for the letterbox and keyhole. Any of these can leak cold air, especially as the door, its seals and its frame age and the door drops or warps slightly on its hinges. People usually notice the draught at the bottom and fit an excluder there, but the sides and top frequently leak as much or more, and the letterbox and keyhole can admit surprisingly strong jets of cold air. So the first thing to understand is that the draught around a front door is rarely a single gap; it is a set of gaps, and a fix aimed at only one of them leaves the others open.

There is also a less obvious source that catches many homeowners out: the junction between the door frame and the wall it is fitted into. When a door is installed, the gap between the frame and the masonry is meant to be sealed, but over time, or where it was never done well, that gap leaks air behind the architrave and plaster — so the cold air seems to come from around the door even though the door itself is shut tight against its seals. This hidden frame-to-wall leakage is why a homeowner can replace all the door's weatherseals and still feel a draught: the air is bypassing the door entirely and coming through the structure around it.

Stopping the draughts properly therefore means locating every leakage path and sealing each in the right way. The door's moving edges need compression or brush seals that close the gap while still allowing the door to operate; the threshold needs a seal or a draught-proof threshold strip matched to the clearance; the letterbox and keyhole need brush or sprung covers; and the frame-to-wall junction needs the gap filled and sealed behind the architrave. Because the relative importance of these paths varies from door to door — and because the hidden frame leak is invisible — the efficient method is to find the leaks first, ideally by feeling for them under the pressure difference a blower door test creates or with a smoke pencil, and then seal the paths that actually matter rather than guessing.

Common causes

Signs and symptoms

Air leaks through a door assembly wherever there is a continuous gap and a pressure difference across it. Wind pressure on the elevation and the stack effect — warm air rising inside and drawing cold air in low down — create that pressure difference, and the front door, often near the foot of a stairwell, sits where the stack effect pulls air in strongly. The flow through a gap rises sharply with its size, so a small clearance under a dropped door or a worn margin down the closing side can carry a substantial volume of cold air, while the letterbox and keyhole act as discrete orifices that produce concentrated jets. Reducing leakage means closing the continuous paths and the orifices so the gaps no longer present an open route under pressure.

The frame-to-wall junction is a distinct and often dominant path because it leaks through the structure rather than the door. The installation gap between the frame and the masonry, if unsealed or poorly sealed, connects the outside air to the interior behind the architrave and plaster, so air bypasses the door's weatherseals entirely. This is why upgrading the door's own seals can fail to cure the draught: the leakage is occurring around the frame, hidden from view, and only sealing that junction — filling the gap and making it airtight behind the trim — addresses it. Because it is concealed, this path is easily missed by an inspection that looks only at the visible door edges.

Locating the paths under a controlled pressure difference is what makes sealing efficient and complete. A blower door test depressurises the dwelling so that all the leakage paths draw air inward at once, allowing each to be felt or traced with smoke and ranked by significance — distinguishing the threshold, the edge seals, the letterbox and the hidden frame junction. Each path then takes the appropriate measure: compression or brush seals on the moving edges that still permit operation, a threshold seal matched to the clearance, sprung covers on the letterbox and keyhole, and filling and sealing the frame-to-wall gap. Sealing in response to the measured paths cures the draught without impeding the door, in contrast to fitting a single excluder and leaving the larger, often hidden, leaks open.

How to stop draughts around a front door

Find every leakage path — threshold, edges, letterbox and the hidden frame-to-wall junction — then seal each appropriately so the cold air is stopped without preventing the door from working.

1. 01

   Locate the leaks

   Feel for or trace the draughts at the threshold, edges, letterbox and frame, ideally under a pressure difference.

2. 02

   Seal the moving edges

   Fit compression or brush seals down the sides and top that close the gap but still let the door operate.

3. 03

   Draught-proof the threshold

   Add a threshold seal or strip matched to the clearance to close the gap at the bottom.

4. 04

   Cover the letterbox and keyhole

   Fit brush or sprung covers to stop the concentrated jets of cold air.

5. 05

   Seal the frame-to-wall gap

   Fill and seal the hidden junction between the frame and the wall behind the architrave.

6. 06

   Adjust a dropped door

   Re-hang or adjust the door so it sits squarely against its seals all round.

How to prevent it coming back

• Seal the sides, top and frame junction, not just the threshold.
• Keep the door adjusted so it meets its seals squarely.
• Fit covers to the letterbox and keyhole.
• Find the leaks before sealing rather than guessing.