What is it?
A threshold strip (or weathering strip) is the narrow trim fitted across the base of a doorway, at the point where the door closes down onto the floor. It covers and seals the joint between the door cill and the internal floor finish.
- 1Floor Finish (timber)
- 2Floor Finish (Stone)
- 3Threshold Strip
What does it do?
It closes the gap under the door against draughts and water, and gives the door leaf something even and durable to seal against as it closes. The floor finish either side of it (screed, tiles, timber) isn't relied on to hold that seal itself. Many threshold strips also carry a brush or rubber seal along their length to improve the draught seal further.
It also protects the edge of the floor finish at the doorway, which is otherwise a high-wear, high-traffic point.
Where is it used?
At the base of external door openings, and internally wherever two different floor finishes meet at a doorway.
How to specify
The strip is chosen to suit the door it pairs with (many are supplied by the door manufacturer as a matched part) and the floor finish either side, since it needs to either sit flush with, or ramp cleanly between, differing floor thicknesses. Where step-free access is required, a low-profile or flush threshold is specified instead of a raised strip.
Due to the intensity of the foot traffic over the strip, it is best to use a solid metal and not apply any kind of paint or other finish as it will rub off over time.
Other considerations
A threshold strip that sits proud of the floor is a trip hazard, and a common one at external doors. This is a real consideration where accessibility or building regulations require a level or near-level threshold. 15mm or below is generally considered to be acceptable.
Interacting elements
- Door: the strip seals against the base of the door leaf when it's closed
- Cill: the strip usually sits directly over or against the cill
- Screed / floor finish: the strip covers the joint between the finish and the door