Can you lay LVT over floorboards?

Why floorboards are a problem for thin planks

Original boards move. They shrink and swell with the seasons, they cup slightly across their width, and the joints between them open and close. Individual boards also sit at marginally different heights where joists have settled or where boards have been lifted for pipework.

None of that matters under a thick carpet with underlay. Under a four millimetre vinyl plank it matters a great deal. Board lines become visible as long shadows across the floor, joints can telegraph as ridges, and glue down planks can lose their bond over a joint that keeps opening.

The standard solution: plywood overboarding

The accepted answer on timber floors is to overboard with plywood, typically six millimetre or nine millimetre, screwed or ring shank nailed at close centres across the whole floor with the sheet joints staggered.

That creates a single, stable, flat platform that does not move with the boards underneath, and it gives glue down LVT something dependable to bond to. It also lifts the floor by only a few millimetres, so doors usually still clear without adjustment.

• Fix at roughly 150 millimetre centres so the sheet cannot lift or drum.
• Stagger the sheet joints rather than lining them up in a grid.
• Punch fixings just below the surface and fill where needed.
• Leave a small expansion allowance at the perimeter, hidden by skirting or scotia.

Before overboarding: the checks that matter

Screw down any loose or squeaking boards first, because plywood over a loose board still moves. Check for damp, especially in ground floor rooms of older properties, and confirm that airbricks and underfloor ventilation are clear rather than blocked by a patio or render.

Also look at pipework and cabling running in notches under the boards. Fixings need to miss them, and a quick photograph of runs before overboarding is worth the two minutes it takes.

When click LVT is the better choice

Click LVT over a thin dense underlay is more forgiving of small imperfections than glue down, because it floats as one sheet rather than following the contour of every board. On a sound but slightly imperfect timber floor it can be the pragmatic option in bedrooms and living rooms.

It is still not a licence to skip preparation. Manufacturers publish a flatness tolerance, commonly around three millimetres over two metres, and a floating floor over larger deviations will feel springy and can click apart at the joints.

What happens if you skip preparation

Usually nothing at all for the first few weeks, which is why the shortcut is so tempting. Problems appear through the first heating season: board lines showing as long stripes in raking light, ridges you can feel underfoot at joints, and on glue down floors, planks lifting slightly where a board has moved.

At that point the only real remedy is to lift the LVT, prepare the floor properly and refit, which means paying for the plank twice. Overboarding first is much cheaper than putting it right afterwards.

Underfloor heating and boarded floors

If there is an electric mat or water system involved, follow the manufacturer's build up rather than improvising. LVT generally works very well over underfloor heating because it is thin and conducts heat readily, but there is a maximum surface temperature, commonly around twenty seven degrees, and it must be commissioned gradually.

Over a boarded floor with heating below, a proper spreader plate or overlay system is doing a job that plywood alone cannot. Ask for the system detail to be named on the quote.