Laminate flooring door thresholds: which bar to buy and how to fit it

The threshold bar a laminate doorway needs comes down to one measurement: the height difference between the two finished floors. Level floors take a T-bar, a step of 3 mm or more takes a reducer, and a floor that stops at an exposed edge takes an end profile. Whichever bar it is, the track fixes to the subfloor of the opening, never through the boards, and sits on the centre line of the closed door so it disappears when the door is shut. The other half of the answer is that many doorways need no bar at all: same laminate both sides and a run under about 8 to 10 m can run straight through, which saved an average of 1.2 bars per house when we measured it across 30 multi-room floors.

Which threshold bar fits which doorway?

Measure both finished heights first, underlay and adhesive included, then read off the bar:

The classic mistake sits in the second and fourth rows. Tile on adhesive frequently finishes 5 to 15 mm proud of laminate on underlay, so a doorway that looks like a T-bar job on the bare subfloor turns into a reducer job once both floors are down. Bars come in metal, solid wood and foil-wrapped MDF at typical prices of £10 to £25 each; the profile shapes and where each belongs between rooms are covered in the transitions pillar.

Do you need a threshold bar at every door?

No, and fitting fewer is usually the better floor. A bar earns its place in four situations:

1. The run is too long. A floating floor needs an expansion break about every 8 to 10 m, and a doorway is the natural place to hide one.
2. The floor changes. Different material, different height or two floors laid at different times each need their own bar.
3. The direction changes. Boards meeting at an angle in a doorway never make a clean joint without a bar over it.
4. You want the rooms isolated. Separate floors can be lifted or replaced one room at a time.

Saving material is not on that list. When we laid the same 30 multi-room floors both ways, one continuous floor averaged 7.0% waste at straight lay against 7.6% for rooms broken at every doorway, and saved those 1.2 bars per house on top. At £10 to £25 a bar, a hallway with four doorways that all run through is a real saving, not a rounding error.

How do you fit a threshold bar in a laminate doorway?

Most bars are a two-part system, a track and a clip-on top, and the whole job is 20 to 30 minutes per door:

1. Measure the opening at floor level between the architraves, and both finished floor heights.
2. Cut the track and top to length, then notch the ends of the top around the door stops. A hacksaw handles metal bars; a fine-tooth saw handles wood and MDF ones.
3. Fix the track to the subfloor on the centre line of the closed door leaf. The bar should vanish under the shut door, seen from either room.
4. Check the gap on both sides. The boards stop 8 to 12 mm short of the track, the same expansion gap they get at every wall, hidden under the reach of the bar's top.
5. Clip the top on with a tapping block and swing the door over it.

Single-piece bars that screw down through their face exist, and so do self-adhesive ones. Both work in light-traffic doorways, but the screw heads stay visible on the first kind and the second kind lets go under trolley wheels and repeated door swings, so the two-part track is the default for a reason.

Screws or adhesive: how should the track be fixed?

Match the fixing to the subfloor, not to whatever came in the packet:

The warning in rows three and four deserves its own sentence: doorways are exactly where pipe runs cross between rooms, and screwing a threshold track blind into a screed is the classic way to find one. A pipe and cable detector costs less than the repair, and where anything shows up, a quality grab adhesive on a dust-free floor holds a track for good; keep the door shut overnight while it cures.

Whatever the fixing, it goes through the track into the subfloor only. The boards on both sides stay free. Fix through the laminate and the doorway pins the floating floor, which comes back later as peaking in summer and gaps opening up in winter.

Will the door still open over the new threshold?

Check before the bar goes down, not after. Three things to look at:

• The clearance. The door leaf wants a few millimetres of daylight over the finished bar. New laminate plus underlay plus a bar can finish higher than the old floor did, especially over a thin old vinyl.
• The trim allowance. Solid doors trim easily; hollow-core doors only carry 10 to 20 mm of solid rail at the bottom before the saw reaches the void, so measure how much needs to come off before committing.
• The board under the door. The board the doorway lands on should be a full-width board, not a thin rip, because the doorway takes the most traffic in the house. Undercutting the frame so boards slide beneath the architrave is its own technique, covered in the doorways and pipes guide.

Plan the thresholds before you buy the floor

Which doorways get a bar and which run through is a planning decision, and it changes the shopping list twice: the bars themselves, and the packs, because buying room by room instead of once for the whole job added half a pack per house in our doorway study. Draw the connected rooms in the layout planner, mark each doorway as a break or a run-through, and the plan returns every board and cut around each opening plus the exact pack count, with the laminate calculator covering the quick per-room estimate. The bar itself takes half an hour to fit; deciding which doorways deserve one is the part worth doing before any money changes hands.