Why floors lift, and how to stop it

SPC, hybrid, laminate and click-lock vinyl are all floating floors. The planks click together edge to edge. They sit over the subfloor, with no glue or nails fixing them down. That makes them faster to install. It is also easier to lift and replace a single plank later.

It also means the core of every plank still moves a little. It expands and contracts with changes in temperature. This is true even of a core that is fully waterproof. Waterproof is about water. It says nothing about heat.

A small gap is left around the room's edge. It also goes at doorways and around fixed cabinetry. Skirting or a trim strip then hides it. It gives the planks somewhere to expand into as they warm up.

Skipping this gap, or leaving too small a gap, causes most of the trouble. It is the single most common reason a floor peaks or lifts at the joins later. Once the planks have expanded, they have nowhere left to go. Something has to give. That shows up as a ridge along a joint, or a slight lift near a wall.

SPC and hybrid's stone-based core copes with heat better than standard vinyl. But it is not immune. A room with large north- or west-facing windows can get hot. Add no shade, and a Queensland summer can heat it enough to make the floor expand past a standard gap. That usually shows as peaking at the joins near the glass. It can also show as a slight lift close to the window.

We flag this at the measure if a room has a lot of unshaded glass. A bigger expansion gap can help. So can a window treatment to cut the direct sun.

Laminate's core is HDF, a wood-fibre board. It moves with both heat and humidity. It moves more than SPC's stone-based core does. That makes the expansion gap even more important on a laminate job. It is one more reason laminate is not the right pick for a sunny room. The same goes for a room with a real chance of water on the floor.

Before any flooring goes down, the subfloor needs to be flat, firm and clean. It should be flat to about 3mm over a 2 metre straight edge. It should also have no sharp steps or ridges. A subfloor that has not been checked and levelled can leave a plank sitting slightly proud in places. That puts extra stress right on the joins. This is exactly where the expansion gap is already doing its job. A solid, flat base and a correctly sized gap work together. Neither one replaces the other.

At the measure, we look at how much unshaded glass a room has. We size the expansion gap and any trims to suit. It is a small, mostly invisible detail once skirting goes back on. But it makes the real difference. A floor with the right gap stays flat for years. One without it can peak at the joins in its first hot summer.

See how the core in each product behaves on our SPC and hybrid flooring page. Or compare all three hard floors in our SPC vs vinyl vs laminate guide.