Door threshold strips: joining two floors neatly at a doorway

The four common threshold profiles

Most doorway joins are solved by one of these.

• Flat or T profile: two floors at the same height.
• Ramp or reducer: one floor higher than the other.
• End profile: a floor that finishes against a hard edge, such as a patio door or tiles.
• Carpet to hard floor: a gripper edge that holds carpet while covering the hard floor's edge.

Why the gap under the threshold matters

Laminate and engineered boards laid as floating floors expand and contract with the seasons. They need an expansion gap at every edge, including doorways. A threshold covers that gap. If the floor is pinned tight under a strip glued down on both sides, it has nowhere to go and can lift or open at joints.

Dealing with different floor heights

Height differences are common when a new wood floor goes next to an old tiled kitchen or a thick carpet. Small differences are handled by a reducer. Larger steps can be a trip hazard, and it is often better to raise or adjust the subfloor so the finished heights sit closer together.

Doors may need trimming after a new floor goes down so they clear the threshold. That is worth including in the flooring quote.

Materials and finish

Thresholds come in solid timber, aluminium and brass effect finishes, and in colours matched to laminate ranges. Solid timber can be stained to match a wood floor; metal is hard wearing in busy doorways. The fixing should be hidden or neat, and the strip cut to the exact width of the opening.

Thresholds at external doors

Back doors, patio doors and bifolds are a different case. The floor meets a door sill rather than another room, and the threshold has to finish the flooring neatly while keeping water and draughts out. An end profile against the sill, with the expansion gap left under it, is the usual answer. Any gap between the sill and the floor should be sealed carefully so water cannot track underneath.

Planning thresholds before the floor goes down

It is easier to decide thresholds at the planning stage than on the day. Knowing which floors meet where lets the right profiles be ordered in matching colours, and lets the installer set out boards so a doorway does not end on a thin sliver of board.

Questions we're asked about this