No matter how good the flooring product, a poor subfloor will cause problems — squeaks, hollow spots, movement in joints, and in extreme cases premature failure. Here is what good preparation involves.
Check for level and flatness
Most manufacturers specify a flatness tolerance of 3mm across a 1.8m span. Your fitter should check this with a straightedge. Concrete floors can be levelled with self-levelling compound. Timber floors may need boards screwed down or planed.
Check for moisture
Excess moisture is one of the most common causes of flooring failure, particularly on ground floors over concrete. Your fitter should carry out a moisture test before any wood-based product goes down. If moisture is present, a damp-proof membrane (DPM) must be applied first.
Remove old flooring
Old flooring, adhesive and gripper rods should be fully removed before new flooring is fitted. Fitting over old flooring reduces headroom, creates movement, and conceals potential subfloor problems.
Timber subfloors
Squeaky or sprung boards should be screwed down. Old hardboard or plywood overlays should be checked for secure fixing. If the floor is uneven, a new layer of plywood (6mm or 12mm) can be laid first.
Concrete subfloors
New concrete must be fully cured (typically 28 days minimum). Cracks or hollow areas should be repaired. Self-levelling compound can correct unevenness of up to 20mm in a single pour.
Acclimatisation
Wood products need to acclimatise in the room before fitting — typically 48–72 hours. Factor this into your schedule. A thorough fitter will walk you through any subfloor issues when they survey the job and include remedial work in their quote.