Best Acoustic Underlay for Flats UK — Reducing Noise Between Floors
Written by our acoustic insulation specialist — 15+ years experience supplying soundproofing to UK homeowners, developers and contractors. About our experts.
Reducing noise between floors in a flat is one of the most challenging — and most important — acoustic problems in UK residential property. Whether you're a freeholder retrofitting a flat or a developer converting a house, choosing the best acoustic underlay for flats can mean the difference between a happy tenancy and an ongoing noise dispute.
The Flat Acoustic Problem
Flats are acoustically complex. Unlike semi-detached houses where noise travels horizontally through walls, in flats the primary transmission path is vertical — through the floor-ceiling assembly between apartments. Every footstep, chair movement, or dropped object on the floor above translates directly into noise for the occupant below.
The floor-ceiling assembly typically consists of:
- The concrete or timber structural floor
- Any floor covering and underlay above
- The ceiling construction below (plasterboard, possibly with resilient fixings)
Both elements contribute to overall acoustic performance. This guide focuses on the floor-side treatment — the underlay — which is the most accessible and highest-impact intervention.
Best Acoustic Underlay for Flats: Our Recommendations
#1: 6mm Recycled Rubber Acoustic Underlay — 74 dB ΔLw
The UK's highest-performance single-layer acoustic underlay at 6mm thickness. For flats on concrete construction — the most common configuration in purpose-built blocks — this underlay installed under a floating floor delivers outstanding impact noise reduction that is immediately noticeable in the flat below.
It is rated for use under screed, making it suitable for new-build flats with liquid screed finishing, as well as refurbishments with traditional floor finishes.
#2: 12mm Acoustic Flooring System — 30 dB impact / 58 dB airborne
Where full Building Regulations Part E compliance is mandatory — particularly in flat conversions where Pre-Completion Testing applies — the 12mm system provides the highest combined impact and airborne performance available in a floor-mounted product.
The 58 dB airborne reduction is critical for conversions where airborne sound is also a significant issue (conversation, music, TV) in addition to footstep noise.
Timber Joist Floors in Flats
Victorian and Edwardian conversions typically have suspended timber joist floors. These are acoustically problematic: the air void between joists resonates, amplifying low-frequency noise, and the timber deck flexes under load.
For timber joist floors:
- Add mass to the deck — high-density boards or screed on top of joists before underlay.
- Specify SilentMat 15mm or the 12mm Acoustic System as the primary underlay.
- Consider resilient ceiling treatment below — a decoupled ceiling adds significant airborne performance.
- Fill joist voids with acoustic mineral wool quilt — reduces airborne resonance substantially.
Practical Installation Advice for Flats
- Don't forget the perimeter detail. The floor-wall junction is the primary flanking path. Turn the underlay up the wall by 15mm at all perimeters and trim after the floor is laid.
- Use flexible sealant at thresholds. Rigid threshold strips create sound bridges. Use flexible acoustic mastic or rubber threshold strips instead.
- Check the flat below. If the tenant below can be involved in before/after listening, it creates useful feedback and reduces disputes.
Managing Expectations
No acoustic underlay eliminates all noise. The goal is meaningful reduction — from clearly audible and intrusive, to barely noticeable. At 74 dB ΔLw, our 6mm Rubber Underlay will deliver a transformative improvement in most flat situations. For exceptional performance where Part E is required, the 12mm system provides the highest achievable results without structural intervention.
Shop for flats: 6mm Rubber (74 dB) | 12mm System | Full Acoustic Underlay Range