How Thick Should Acoustic Underlay Be? Expert Answer

Written by our acoustic insulation specialist — 15+ years experience. About our experts.

This is one of the most common questions our team receives — and the honest answer is: thickness matters less than material and density.

The Thickness Myth

Many buyers assume that thicker acoustic underlay automatically means better performance. This is not correct. A 3mm high-density rubber mat often outperforms a 10mm open-cell foam underlay on acoustic metrics. The key measurement is ΔLw — not millimetres.

Recommended Thicknesses

• 3mm: Our 3mm rubber (54dB) — minimum for meaningful acoustic improvement. Good for tight floor build-up situations.
• 6mm: Our 6mm rubber (74dB) — the optimum for most applications. Best balance of performance, floor raise, and cost.
• 12mm: Our 12mm system — maximum performance, for Part E compliance and serious noise problems.
• 15mm: SilentMat 15mm — for heavy-use commercial or premium residential where underfoot comfort is also a priority.

How Much Height Will I Lose?

The floor raise equals the underlay thickness. A 6mm underlay raises your finished floor by 6mm. Check threshold heights, door clearances, and stair riser heights before specifying.

Browse our acoustic underlay range or contact our experts for a free recommendation.