Acoustic Underlay vs Floating Floor — Which Do I Need?
Written by our acoustic insulation specialist — 15+ years experience supplying soundproofing to UK homeowners, developers and contractors. About our experts.
If you're researching floor noise solutions, you've probably come across two main approaches: acoustic underlay and floating floor systems. The terminology can be confusing — especially since acoustic underlay is often part of a floating floor system. This article clarifies the difference, explains when each approach is appropriate, and helps you decide which to specify for your project.
What Is Acoustic Underlay?
Acoustic underlay is a layer of resilient, high-density material laid between the subfloor (concrete slab, timber boards, or screed) and the floor finish (engineered wood, LVT, laminate, carpet). It absorbs impact energy from footsteps before it enters the building structure, reducing the noise transmitted to rooms below.
Our range includes:
- 3mm Recycled Rubber — 54dB ΔLw. Entry-level performance, minimal height change.
- SilentCloud 6mm — Premium residential underlay for floating floors.
- 6mm Recycled Rubber Pro — 74dB ΔLw. Industry-leading performance, Part E compliant.
- Cork Rubber — Natural composite; acoustic + thermal insulation in one layer.
What Is a Floating Floor?
A floating floor is a floor installation method where the floor finish (boards, tiles, or panels) is not mechanically fixed to the subfloor. Instead, it sits on top of the underlay and relies on its own weight and the locking joints of the boards to stay in place. There are no screws, nails, or adhesive to the subfloor.
A floating floor requires an underlay — without one, the floor would be rigid and transmit impact noise directly. So "floating floor system" usually refers to the combination of acoustic underlay + floating floor finish.
Key Difference: The Two Are Complementary, Not Competing
Acoustic underlay = the resilient layer
Floating floor = the installation method
A floating floor system = acoustic underlay + floating finish
The question isn't "which do I need?" — it's "which underlay do I need, and should my floor finish be floating or fixed?"
When to Choose Acoustic Underlay Only (Fixed Floor)
Sometimes a fixed (glued or nailed) floor finish is preferable or necessary, and you still want acoustic performance. In these cases, use acoustic underlay designed for the specific application:
- Under screed: 6mm Rubber Pro — suitable for liquid and sand-cement screed poured over it (floating screed method)
- Under tile on boards: Cork rubber or specialist acoustic membrane
- Under carpet: Replace standard carpet underlay with acoustic cork rubber
When to Choose a Floating Floor System
A floating installation is recommended when:
- Maximum acoustic performance is required — floating minimises rigid contact between finish and structure
- Floor height is a consideration — no fixings means a thinner installation profile
- The subfloor is uneven — floating floors tolerate minor undulation better than glued installations
- The floor is likely to be changed in future — floating floors are fully reversible
For maximum floating floor acoustic performance, use AcoustiLay 8 — the 12mm system delivers 30dB impact + 58dB airborne as a complete floating floor underlayer.
Performance Comparison
| Configuration | Impact Reduction | Airborne Reduction | Floor Height Added |
|---|---|---|---|
| No underlay (hard floor direct) | 0dB | 0dB | 0mm |
| 3mm rubber underlay + floating LVT | 54dB ΔLw | Minimal | ~11mm |
| 6mm rubber pro underlay + floating engineered wood | 74dB ΔLw | Moderate | ~21mm |
| AcoustiLay 8 + floating engineered wood | 30dB system | 58dB system | ~27mm |
FAQs
Can I use acoustic underlay under a glued floor?
Some acoustic underlays are designed for glued installations — check compatibility. Generally, standard foam or cork underlays are not suitable for glued floors. For floating screed poured over an acoustic layer, use our 6mm Rubber Pro, which is specifically engineered for this.
Is a floating floor noisier to walk on?
Without good underlay — yes. A thin underlay under a floating engineered floor can produce a hollow, drum-like sound underfoot. A high-density acoustic underlay (like 6mm rubber) eliminates this, providing a solid, quiet feel.
Do I need both acoustic underlay and soundproofing membrane?
In most residential applications, a single high-performance acoustic underlay is sufficient. For recording studios, home cinemas, or very high-specification residential projects, layering an acoustic underlay with a mass loaded vinyl membrane can add an additional 5–8dB of airborne isolation.