How do I replace a door threshold strip?

A threshold strip covers the join between two floors and takes more foot traffic per square inch than anything else in the house. Getting the profile right matters more than the fitting.

Safety

What you'll need

• Hacksaw or mitre saw with a metal blade, and a file
• Drill, screwdriver and appropriate plugs
• Tape measure and a straightedge

Step by step

1. Work out what the strip has to do.Joining two floors of equal height needs a flat or T-bar profile. A step between them needs a ramp or a reducer. An external door needs a weather bar. The wrong profile is the commonest error.
2. Measure the level difference.A straightedge across the doorway with the gap measured underneath. Even a few millimetres decides between a flat strip and a reducer.
3. Measure the width at the narrowest point.Door openings are rarely exactly parallel. Measure at both ends and the middle and cut to the smallest, since a strip that is slightly short is far easier to live with than one that will not go in.
4. Choose the material for the traffic.Aluminium is hard-wearing and cheap. Solid wood suits timber floors and can be stained to match. Plastic is the cheapest and the first to break.
5. Remove the old strip carefully.Screws out, then lever gently. Old ones are often glued as well — patience here saves damaging the floor edges either side, which are hard to repair.
6. Clean out the gap.Old adhesive, grit and offcuts. The new strip needs to sit flat, and anything left underneath makes it rock, which is what loosens fixings.
7. Check the expansion gap is still there.Laminate and engineered floors need a gap at every doorway to expand into. Do not fill it or fix through it — the threshold's job is to cover that gap, not close it.
8. Cut with a fine metal blade.A hacksaw with the strip well supported, or a mitre saw with a metal-cutting blade. Cut slowly; forcing it distorts the profile.
9. File the cut ends.Aluminium leaves a genuinely sharp edge and a burr that stops the strip seating. A few passes with a file makes it safe and makes it fit.
10. Fix into the subfloor, not the finish.Screws should reach the boards or screed beneath. Fixed only into laminate or a floating floor, the strip works loose and stops the floor moving as it should.
11. Predrill on hard surfaces.Concrete or tile needs a masonry bit and a plug. Driving a screw straight into either cracks the tile or simply does not hold.
12. Countersink the screws.Heads must sit flush or below. A proud screw head in a doorway catches feet, socks and vacuum cleaners within a week.
13. Seal an external threshold.A bead of exterior silicone along the outer edge. It is part of the weather seal and an unsealed one lets water into the floor structure.
14. Check the door still clears it.Open and close it fully. A new strip that is thicker than the old one can catch the door, which then needs easing at the bottom.
15. Test it underfoot.Walk over it in both directions. Any rock, click or lift means it is not bedded down, and a threshold that moves will loosen and become a trip hazard.

Tips

• Measure the level difference first. Profile choice matters more than anything else in this job.
• Fix into the subfloor. A strip screwed only into a floating floor stops it expanding and works loose.
• File the cut ends. An unfiled aluminium edge is sharp and stops the strip sitting flat.

Common mistakes

• Screwing through a floating floor into the subfloor — Laminate and engineered boards must be free to expand. Pinning them at a doorway causes buckling elsewhere in the room, sometimes months later.
• Cutting to the widest measurement — Door openings are rarely parallel, so a strip cut to the widest point will not go in. Cut to the narrowest and the small gaps at the ends are invisible.

If it doesn't work

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