6mm Acoustic Underlay Review — Is It Worth It?

Written by our acoustic insulation specialist — 15+ years experience supplying soundproofing to UK homeowners, developers and contractors. About our experts.

If you're searching for a 6mm acoustic underlay review, chances are you're weighing up whether the extra cost over a standard foam underlay is justified. The short answer is yes — categorically, unequivocally yes. But let's look at the data and real-world performance rather than just marketing claims.

What Is the 6mm Acoustic Underlay?

Our 6mm Recycled Rubber Acoustic Underlay is a high-density recycled rubber product manufactured from post-industrial and post-consumer rubber waste. It is produced at a consistent 6mm thickness with a density typically in the range of 900–1,100 kg/m³ — far above standard foam underlays which typically measure 25–35 kg/m³.

That density is the key to acoustic performance. Sound is mechanical energy. Stopping it requires mass, resilience, or both. High-density rubber provides both.

Performance Data: What 74 dB ΔLw Actually Means

The headline figure is 74 dB ΔLw (weighted impact sound improvement). This is measured to ISO 10140-3 using a standardised tapping machine on a concrete reference slab.

To put it in context:

• Standard foam underlay: typically 20–30 dB ΔLw
• Cork underlay: typically 45–55 dB ΔLw
• Our 3mm Recycled Rubber: 54 dB ΔLw
• Our 6mm Recycled Rubber: 74 dB ΔLw

A 20 dB difference between the 3mm and 6mm is not a minor uplift — it represents approximately 10× more sound energy absorbed. In practice, this means footsteps that were clearly audible through the 3mm underlay become barely detectable through the 6mm.

Where It Excels

Under Screed

One critical advantage: the 6mm Rubber Underlay is specifically rated for installation beneath liquid screed and sand/cement screed. It withstands the alkaline chemistry and compressive loads of fresh screed without degradation. Few other underlays at this price point offer this capability.

Building Regulations Part E

For residential separating floors, this underlay — correctly installed under a floating floor — achieves the impact noise target of L'nT,w ≤ 62 dB for conversions and contributes significantly to achieving the ≤ 45 dB new-build target. Performance certificates are available for project submissions.

Longevity

Recycled rubber does not compress permanently under floor loads. Unlike foam underlays which degrade within 5–10 years, the 6mm rubber maintains its acoustic properties for 30+ years under normal residential use. This is not a consumable — it is a long-term investment in the acoustic environment of the building.

Honest Limitations

No underlay is perfect for every situation. The 6mm product:

• Raises floor height by 6mm — significant at door thresholds and adjacent to stairs
• Has a higher TOG value than our thinner products — check UFH system compatibility before specifying
• Is heavier to handle than foam products, though rolls are manageable

If height is a critical constraint, consider our 3mm Recycled Rubber (54 dB ΔLw) or Cork Rubber Composite instead.

Is It Worth It?

If you're installing a hard floor in a flat, conversion, or any multi-occupancy building, the 6mm acoustic underlay pays for itself many times over. Noise complaints from neighbours, failed Building Control inspections, and retrofit acoustic treatment are all vastly more expensive than specifying the right underlay at the outset.

For pure impact noise performance at 6mm thickness, nothing on the UK market matches the 74 dB ΔLw rating of our 6mm Recycled Rubber Underlay.

Browse our full acoustic underlay range: Acoustic Underlay Collection