9-Step Plan to Draught-Proof a Front Door With Stormguard Seals for 20% Less Heat Loss

Find the moving air before buying seals

Hold a lit incense stick or a narrow strip of tissue about 20mm from the door edge while the door is shut. Choose a windy day if possible, then move slowly down both jambs, across the head, along the threshold, and around the letterplate flap. Smoke pulled sideways, or tissue lifting toward the gap, shows the leak path clearly. Most front doors fail at three or four distinct points, and the threshold under the door usually leaks the most because gravity-driven cold air drains through the largest visible gap there.

Mark each leak with a pencil tick on the frame. Measure the gap with a feeler gauge or a folded paper shim. A 2mm gap needs a different seal profile from a 6mm gap, and Stormguard publishes seal ranges by gap width. Buying a 3mm to 5mm compression strip for a 7mm gap leaves the leak in place. Record whether the door is timber, composite, or uPVC, because self-adhesive foam holds poorly on dusty or flaking paint and needs a cleaned, dry surface first.

Fit the threshold seal before the other edges

The single largest leak on a typical hinged front door sits under the bottom edge. A brush strip or flexible blade seal closes it.

There are two common ways to deal with that gap. One is a draught excluder screwed to the bottom face of the door itself. The other is an aluminium threshold bar with an integral rubber insert fixed to the floor. Exitex and Stormguard both make the door-mounted brush type, sold in 838mm and 914mm widths to suit standard UK door leaves, and both types can be cut down with a hacksaw.

Take the width measurement along the bottom edge, since old timber doors are rarely square. Hold the brush carrier against the bottom edge with the door shut, then adjust the height until the bristles just graze the floor or the threshold. They should touch without dragging.

Dragging bristles wear out inside two winters and can stop the door swinging freely. Fix the carrier with the supplied screws into pilot holes drilled at 6mm centres from each end, then test the swing before moving on to the jambs.

An uneven stone or tiled floor changes the choice of seal. A flexible blade type follows dips more reliably than a stiff brush, since a single rigid line leaves crescent-shaped gaps over any hollow in the floor.

Use the nine steps in order

Each seal changes how the door closes, so the order of fitting matters. Put the threshold seal on first, then check the latch before adding compression seals elsewhere.

1. Clean both jambs, the head, and the bottom edge with sugar soap, then let them dry fully.
2. Smoke-test the door and mark every leak point with a pencil.
3. Measure each gap width with a feeler gauge and write it down.
4. Buy Stormguard or Exitex profiles matched to those exact widths.
5. Fit the threshold seal first and test the door swing.
6. Apply self-adhesive E-profile or P-profile compression seal down both jambs.
7. Run the same compression profile across the head, butting it to the jamb seals.
8. Fit a two-flap brush letterplate cover or an internal sprung letterplate seal.
9. Close the door, repeat the smoke test, and mark any remaining leak for a second pass.

Use P-profile on gaps between 3mm and 5mm. E-profile is made for tighter spaces, from 2mm to 3.5mm. If a 5mm P-profile is pressed into a 2mm gap, the door may stop latching. That mismatch is the common reason a newly draught-proofed door suddenly refuses to shut on the first cold night after fitting.

Put compression seal on the frame stop

The vertical and top gaps on a closing door compress when the latch pulls home, which is why foam or rubber compression seal works there. A brush is a poor fit for those edges. Self-adhesive EPDM rubber holds a shape change for years, while cheap PVC foam can flatten permanently inside a season and then stops sealing. Stormguard sells EPDM in brown, white, and grey to match common frame colours, in 5m and 10m rolls.

Peel and stick the profile to the frame stop, the raised lip that the door closes against. Leave the door face itself clear. Start at the top corner, work down one jamb, and keep the strip straight. Cut it square at the threshold seal with sharp scissors, then repeat the process on the second jamb.

Fit the head section last. It needs to butt tight against both vertical strips so no corner gap survives. Press the whole length down hard with a thumb for adhesion, especially at the corners. Adhesive failure almost always begins at an unpressed corner, where the strip later peels and curls. After fitting, the door should need a deliberate push to latch. That resistance is the seal compressing, and it shows the profile is doing its job.

Seal the letterplate as its own leak

A standard 260mm by 50mm letterplate aperture can move a surprising volume of cold air because the sprung flap rarely seals by itself. A two-flap brush seal screwed to the inside face of the door, or an internal hinged cover plate, closes the slot while still allowing post through.

Fit the brush seal centred over the existing aperture with the two supplied screws, checking first that the bristles do not foul incoming letters.

Worked example: a 1930s timber front door

Take a painted softwood front door in a semi-detached house. It is 838mm wide, with a 6mm threshold gap, 3mm gaps at both jambs, a 2mm head gap, and an unsealed letterplate.

The shopping list is short: one 914mm Exitex brush threshold strip cut down to 838mm, one 10m roll of Stormguard 3mm to 5mm EPDM P-profile for the two jambs and the head, and one brush letterplate seal. The jambs measure roughly 1980mm each, and the head adds another 838mm. Together they need about 4.8m of compression seal, so a single 10m roll leaves enough margin for trimming errors.

At typical UK DIY-shed prices, the materials fall in the 25 to 40 pound range. Fitting takes one unhurried afternoon. The threshold strip deals with the widest opening under the door, and the jamb and head seals then reduce the next largest combined leakage area. For a door that had been contributing a meaningful slice of the home’s 15 to 25 percent air-leakage loss, sealing all four paths removes the bulk of that door’s share.

The reason the lower edge matters so much is simple arithmetic: gap area multiplied by the pressure difference across it. Closing the 6mm threshold gap, the widest of the four, gives the most heat retained for each pound spent.

One caution from the same example is the door shape. A long steel rule held against the closed edge reveals a 3mm bow in the middle of one jamb. A single uniform 3mm seal would leak at the bow and bind at the ends, so that jamb needs a slightly thicker profile to bridge the deeper section, with firmer compression at the top and bottom.

If the door face still feels cold

The seals above stop air movement around the edges and the letterplate. Conducted heat through the door slab still travels across the whole face of a solid timber or hollow composite door, and no edge seal changes that part of the loss.

If the smoke stays still after sealing and the door face still feels cold to the palm, the remaining loss is conduction through the slab, which points beyond edge seals toward a heavier curtain, a thermal door blind, or a replacement slab. The smoke test has no way to rank those choices.