Why floors move

Even sealed flooring responds to changes in humidity and temperature. Across a typical UK winter-to-summer cycle, a 5-metre run can shift by 5–8mm. If the floor cannot move, it lifts, buckles, or splits at the joints.

The standard 8–10mm gap

Leave an 8–10mm gap around every fixed obstacle: walls, kitchen units, door frames, hearths, pipes. This is hidden by skirting or scotia trim once the floor is laid, so it never shows.

Doorways and threshold strips

Anywhere a flooring run continues through a doorway, fit a threshold strip and keep the expansion gap underneath it. The same applies at the join between two different floor finishes — for example wood meeting tile.

Long runs need expansion strips

For runs over 12m in any one direction, or L-shaped rooms where one leg is over 8m, fit an intermediate expansion strip mid-floor. It looks like a slim metal or matching trim line and prevents the floor lifting in the middle on a hot day.

Common mistakes

• Skirting fitted hard to the floor, eliminating the gap. It should always sit on top with a 1–2mm shadow line, never crush.
• Gap shut off by silicone instead of trim. Silicone is rigid once cured and stops the floor moving.
• Underfloor pipes filling the gap. Pipes should pass through a routed slot, not sit tight against the floor edge.

If the floor has already lifted

If you can see a wave or a peak, check that skirting and trim are not crushing the perimeter. Often releasing one section and trimming the panel ends back to recreate the 8mm gap solves the problem within a few days as the floor relaxes.