Laying wood flooring or vinyl over a floor with unevenness without correcting it first is one of the most expensive mistakes in a renovation: the problem isn't visible when finished, but shows up months later with creaks or pieces that move.
What self-levelling compound does
Self-levelling compound is a fluid mortar that is poured and spreads by itself, leaving a flat base ready for the final floor covering. It is essential before wood flooring or vinyl over uneven substrates — these floorings, being thin and rigid, transmit any unevenness in the original floor.
How consumption is calculated
Consumption (kg) = Area (m²) × Layer thickness (mm) × 1.5
Worked example: to level 20 m² at 5 mm thickness: 20 × 5 × 1.5 = 150 kg, rounded up to 6 bags of 25 kg. This is the same calculation the PresupuestoYa calculator applies automatically for the Floor Layer trade.
Drying time is non-negotiable
Always respect the manufacturer's drying time before installing on top: walking or laying flooring on self-levelling compound that hasn't fully cured can leave marks or compromise the flatness achieved — all the levelling work is lost if it's stepped on too soon.
Underlay under wood flooring: not just filler
The foam underlay laid under floating wood flooring cushions footfall noise and compensates small irregularities in the floor. In flats with neighbours below, a foam with good impact-noise insulation makes a real difference — it isn't a simple filler, it's part of the final acoustic behaviour of the floor. It is bought with a 5% margin for overlaps.
Frequently asked questions
How much self-levelling compound do I need for 30 m² at 10 mm thickness? 30 × 10 × 1.5 = 450 kg, rounded up to 18 bags of 25 kg.
Can I install wood flooring directly on freshly applied self-levelling compound? No: the drying time stated by the manufacturer must be respected, or the flatness achieved can be compromised.
What's the insulating underlay for if the wood flooring already has its own backing? It cushions footfall noise and compensates small irregularities in the floor — it is part of the final acoustic insulation, especially relevant in flats with neighbours below.
Conclusion
Calculating the self-levelling compound by the real thickness needed, and respecting the curing time before walking on it, is what stops a flatness problem reappearing months later under the wood flooring or vinyl. The insulating underlay, although hidden, is still a real item that affects the acoustic comfort of the finished floor.
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