Seal a Draughty Exterior Door in Two Minutes With the Screws Already in Its Threshold

The Problem

Air comes in under the front door, and the standard response is to block it — a draught excluder, a rolled towel, a bean bag along the sill. It works, badly, and it has to be moved every time the door opens.

The gap is usually not a design flaw or a worn sweep. It's a threshold that has settled out of adjustment, on a door that was built to be adjusted.

The Technique

Look at the threshold — the metal or composite strip across the sill that the door closes onto. If there's a row of screws set into it along its length, usually three or four, the threshold is adjustable. The screws don't fasten it down; they jack the top plate of the threshold up and down.

1. Close the door and look at where it meets the threshold. Daylight, or a visible gap between the door's bottom sweep and the sill, is what you're closing.
2. Set a screwdriver into each screw in turn and adjust it, working along the row rather than winding one screw all the way. Which direction raises the threshold varies by manufacturer, so turn one a little and watch the strip.
3. Close the door and check after each pass. You want the sweep in firm contact with the threshold along the whole width.
4. Stop when the gap closes. Keep the adjustment even end to end, so the strip stays level rather than tipped.