Fit a door threshold strip between two floors

Measure, cut and fix a threshold strip between two floors, using the right method for concrete or timber subfloors safely.

TH-01Choose the right threshold stripScrew-down strips (metal or wood) are the sturdiest choice and cope well with an uneven gap or a step between floor levels. Self-adhesive strips are easier to fit but only suit a level, low-traffic doorway. Buy a strip a little longer than your doorway so you can trim it to fit.

1 each · Screw-down threshold strip, 900mm

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1 each · Self-adhesive threshold strip, 900mm (alternative)

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TH-02Measure the doorway and mark the cut lengthMeasure the gap wall-to-wall at floor level, right where the door line sits. If the strip sits between two hard floors, leave a 2-3mm gap at each end for expansion. Mark the cut line on the strip with a pencil and a straight edge.

1 each · Pencil

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TH-03Check what's under the floorLift or peel back any old beading or strip to see the floor build-up at the threshold. Tap the floor: a dull, solid sound means concrete or screed; a hollow sound, or visible floorboards or chipboard sheet, means a timber subfloor. This decides which fixing method you use later, so check both sides of the doorway if the rooms have different floor types.

TH-04Check for pipes and cables before you drillCables and pipes can run under floors too, especially near doorways to kitchens and bathrooms, or anywhere with underfloor heating. Run a cable and pipe detector over the area, but still treat the floor as if something is there even after a clear scan — detectors miss deep, boxed-in or heavily embedded runs. Before you drill, find your stopcock (usually under the kitchen sink) and check it turns freely. If there's underfloor heating nearby or any doubt at all, isolate the relevant circuit at the consumer unit before drilling.

1 each · Cable and pipe detector

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TH-05Cut the strip to lengthCut along your marked line with a junior hacksaw, keeping the blade square to avoid a ragged edge. File the cut end smooth so it doesn't catch bare feet or socks.

1 each · Junior hacksaw

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1 each · Metal file

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TH-06Fix a screw-down strip to a concrete or screed floorPosition the strip and mark the fixing holes with a pencil through the strip. Drill 6mm holes to 25-30mm deep with a masonry bit, tap in a wall plug at each mark, then screw the strip down with 25mm screws. Don't overtighten — the strip should sit flat without bowing.

1 each · Masonry drill bit, 6mm

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1 pack · Wall plugs, 6mm (Rawlplug)

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1 pack · Wood screws, 25mm

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TH-07Fix a screw-down strip to a timber or chipboard floorMark the fixing holes as before. Drill a 2-3mm pilot hole at each mark straight into the timber or chipboard subfloor — no plug needed. Screw the strip down with 25mm wood screws, checking it sits flat and doesn't rock underfoot.

1 each · Wood drill bit, 2.5mm

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1 pack · Wood screws, 25mm

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TH-08Fit a self-adhesive strip instead (no drilling)If you've chosen a self-adhesive strip, clean and dry the floor thoroughly first — grease or dust will stop it sticking. Peel back the backing a little at a time, press the strip down firmly along its length, and weight it or stand on it as the product instructions say, usually for a few hours before you walk over it normally.

1 pack · Surface cleaner or degreaser wipes

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TH-09Check the door swings freelyOpen and close the door several times to make sure it clears the new strip and doesn't catch or drag. If it catches, the door itself needs trimming at the bottom — that's a separate job and not something to force with the strip.

TH-10Clean upVacuum up any metal filings, wood dust or screw swarf from around the threshold — sharp filings left on the floor are easy to kneel or stand on later. Wipe the strip clean and dispose of any packaging and off-cuts.

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