Floor Optimizer
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Expansion gap calculator

Enter your room size and floor material, and this calculator gives you the expansion gap to leave on every side, the laying area once the gap is subtracted, and whether the run is long enough to need a mid-floor expansion joint. Everything runs here on the page, with nothing to install and no signup.

Floating floors move with humidity, so laminate, click LVT and floated engineered wood all need a perimeter gap, typically 8 to 12 mm. The part most people miss is that long rooms need more than a gap: past about 8 m of unbroken run, most manufacturers require a deliberate break covered by a threshold profile, and that requirement is a warranty condition.

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Expansion gap, every side
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Laying area after the gap
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Mid-floor expansion joint

The designer plans the gap into the layout for you: walls and obstacles are inset automatically, so the last-row width and pack count come out right.

Design your floor free

The gap changes your measurements, not just your fitting

The laying area is the room minus the gap on every side, and every obstacle cut-out grows by the gap all round. On a 4 m wide room, 10 mm per side removes 20 mm, occasionally exactly the difference between a comfortable last row and a sliver.

The gap must go around everything

Walls, pipes, columns, kitchen islands, hearths and thresholds. One tight pipe hole pins the floor at that point, and the floor buckles around the pin. Radiator pipes get a hole 20 mm larger than the pipe, covered with a rosette.

Skirting decides your maximum

Standard skirting covers 12 to 15 mm comfortably, scotia a little less. If the existing skirting stays on, its cover width limits the gap you can hide, so check before committing to 12 mm.

Frequently asked questions

How big should the expansion gap be for laminate flooring?
8 to 12 mm at every wall and fixed object, with 10 mm the common recommendation. Rooms over about 8 m in either direction need the larger figure and usually a mid-floor expansion joint. The manufacturer sheet is the warranty document, so it has the final word.
When do I need an expansion joint, not just a gap?
Once an unbroken run passes about 8 m in either direction, and usually at doorways between rooms. The joint is a small break covered by a threshold profile, and a doorway is the natural place to hide one.
Does glue-down LVT need an expansion gap?
Barely. Glue-down LVT is bonded to the subfloor, so it cannot drift the way a floating floor does, and perimeter gaps shrink to a few millimetres or none. The adhesive spec decides, not the flooring folklore.
What happens without an expansion gap?
The floor expands against the wall, has nowhere to go, and buckles upward, usually at the middle of the room in the first humid season. The fix means taking boards up back to the wall and recutting, so the 10 mm is cheap insurance.