How to replace a door threshold

Video: How to Fit a Stormguard and a Weather Bar to a Door. This walk-through covers the full process of fitting a low-profile Stormguard threshold and rain deflector to an exterior door — watch it at youtube.com/watch?v=Nai3IkJta9k. The section on checking the clearance between the bottom of the door and the threshold before you drill anything is particularly worth watching, as getting this wrong is the main cause of a door that won’t close properly after fitting.

1. Understand what you have and what you need

Door thresholds come in a few different types. An internal door bar is a flat or T-shaped aluminium or brass strip that covers the join between two different floor finishes — laminate on one side, carpet on the other, for example. An exterior threshold is a heftier thing: it typically has a rubber or neoprene seal on the underside that compresses when the door closes, creating a draught- and rain-proof barrier across the bottom of the door frame.

For most exterior doors in UK homes, you are likely looking at a combined threshold and weather bar system — a low-profile aluminium extrusion that screws to the floor at the base of the door, with a separate rain deflector strip screwed to the door bottom itself. Stormguard is one of the most widely available brands in the UK and does the job well. Work out which you need before buying anything: measure the door width, check the gap between the door bottom and the floor, and decide whether you need a threshold only, a weather bar only, or both.

2. Remove the old threshold or clear the area

If there is an existing threshold in place, unscrew it. Old thresholds are often held down with just two or three screws and should lift out cleanly once those are removed. Some older aluminium strips are bonded down with adhesive as well — if yours is, run a Stanley knife along both edges to cut through the sealant, then lever it up gently with a wide chisel. Try not to gouge the floor covering.

Once it is out, clean up the floor surface underneath. Remove any old sealant, dried adhesive, or rust stains. If the floor is concrete and the old fixings have left crumbling edges around the screw holes, fill them with a small amount of rapid-setting filler and let it cure before you drill new holes. You want a clean, flat surface for the new threshold to sit on.

3. Measure and cut the new threshold to length

Measure the doorway width between the door stops (the raised strips that the door closes against on the frame) rather than between the outer edges of the frame itself. The threshold should sit within the door stops, not overlap them. Mark the measurement on the threshold strip with a pencil and square.

A junior hacksaw or a fine-toothed mitre saw will cut aluminium cleanly. Clamp the threshold securely before cutting — aluminium has a tendency to chatter and vibrate if it is not held down, and a chattering blade leaves a ragged edge. Cut on the waste side of your mark and file the cut end smooth with a metal file. Sharp aluminium edges will go through a sock in seconds and are not much kinder to floor coverings.

4. Check the door clearance before drilling anything

This is the step that catches people out. Lay the threshold in position — do not fix it yet — and close the door onto it. Check whether the door closes fully and the latch engages. If the threshold is too tall or sitting proud, the door will catch on it and you will have a door that will not close properly. That is a much bigger problem to solve after the fact.

Most modern low-profile thresholds are specifically designed to work with doors that have a standard gap underneath, but it is always worth checking. If the door is a tight fit, you can sometimes plane a small amount off the door bottom to create the necessary clearance. If the door is very low-slung and there is almost no gap, a surface-mounted threshold may not be the right solution — a threshold fitted into a rebate in the floor or a different style of draught seal might work better. It depends on the specific door and frame combination.

5. Fix the threshold to the floor

Mark the screw hole positions through the fixing holes in the threshold base. Remove the threshold and drill pilot holes — use a masonry bit if the floor is concrete or stone, a wood bit if it is timber. Plug concrete or stone holes with the appropriate wall plugs. For a tiled floor, use a tile drill bit and be careful with the pressure — cracking a tile right in the doorway is not the end of the world but it is annoying and it looks poor.

Apply a thin bead of flexible sealant along the underside of the threshold base before screwing it down. This prevents water tracking under the strip during heavy rain. Screw it down firmly but do not overtighten into plugged masonry holes — you will just pull the plug out. Wipe away any excess sealant that squeezes out from the edges before it skins over.

6. Fit the weather bar to the door bottom and test the seal

If you are also fitting a weather bar to the door itself, hold it against the bottom face of the door and mark the screw positions. Drill pilot holes into the door and fix the bar in place. The weather bar should overlap with the threshold below when the door is closed, compressing the rubber seal between the two. This is what creates the actual draught- and weatherproof barrier.

Close the door slowly and feel for resistance as the weather bar meets the threshold seal. You want firm, even contact across the full width. If one end is sealing and the other is not, check that the threshold is sitting flat and level — a slight twist in the floor or frame can cause uneven contact. A thin packer under the low end of the threshold will usually sort it. Open and close the door half a dozen times to make sure everything moves freely, the latch engages properly, and the seal compresses consistently. That should be it — a proper weather-tight seal with no draught, no rain creep, and no winter whistle.

When to call a handyman

Call Richard if the door bottom has rotted or warped so badly that the gap is uneven and no standard threshold will seal it properly, if fitting the threshold means planing the door bottom and you are not set up for that, or if the issue turns out to be a failing door frame or damaged sill rather than just the threshold itself. Sometimes what looks like a simple threshold job opens up into a bigger repair once you get the old strip out — damp, rot, and subsidence are all common enough in older properties around Sandwich and the Stour valley. Better to know what you are dealing with early. Get in touch and Richard can have a look.