10mm Acoustic Underlay UK: When You Need Maximum Noise Reduction
Most acoustic underlay specifications for UK residential floors default to 3mm or 5mm rubber. These thicknesses are the correct choice for the majority of domestic applications. But there is a distinct class of project where 10mm acoustic underlay is the right — and sometimes the only compliant — specification: purpose-built flats, residential conversions, and any project where separating floor performance must demonstrably meet Part E of the Building Regulations.
This guide covers exactly when 10mm is required, what the Decimat 10mm achieves, which floor types it suits, and how it compares with standard specification underlays.
When Is 10mm Acoustic Underlay Specified?
10mm acoustic underlay is specified by architects, acoustic consultants, and main contractors in situations where the ΔLw contribution of the underlay alone must be maximised to achieve the required overall floor performance. Typical applications include:
- Residential conversions: Commercial-to-residential or house-to-flats conversions where existing floor construction provides limited inherent sound isolation
- Timber frame new-build: Lightweight timber frame construction has poor inherent mass; 10mm underlay compensates
- Refurbishment of older concrete buildings: Victorian and early 20th century concrete floors often lack the topping mass needed for Part E compliance without maximum-performance underlay
- Acoustic consultant specification: Where an in-situ acoustic test is required and the consultant specifies the underlay ΔLw needed to achieve L’nT,w ≤ 62 dB (new-build) or ≤ 64 dB (conversion)
- Hotels and student accommodation: Where comfort standards exceed Part E minima and specifiers require the best available underlay performance
- Commercial-residential mixed use: Where a commercial ground floor directly adjoins residential upper floors
Decimat 10mm: Product Specification
Our Decimat 10mm acoustic underlay is the highest-performance rubber underlay in the Rubberco range. Key specifications:
- Thickness: 10mm (±1mm tolerance)
- Material: High-density recycled rubber compound
- Density: 1,200–1,400 kg/m³
- Impact noise reduction (ΔLw): 23–28 dB (ISO 9052-1)
- Dynamic stiffness: Low — suitable for resilient layer in heavyweight floor systems
- UFH compatible: Yes
- Roll width: 1.0m standard; cut-to-size available
- Coverage: Typically 10m rolls
- Standards: Tested to BS EN ISO 717-2 and ISO 9052-1
Part E Compliance: What 10mm Acoustic Underlay Contributes
UK Building Regulations Part E (Resistance to the Passage of Sound) sets impact sound requirements for separating floors in residential buildings:
- New-build: L’nT,w ≤ 62 dB
- Conversions and material change of use: L’nT,w ≤ 64 dB
These in-situ measurements depend on the entire floor system — not just the underlay. However, the underlay's ΔLw contribution is critical: a higher ΔLw means the rest of the floor build-up can be less complex (or less expensive) to achieve the target L’nT,w.
At 23–28 dB ΔLw, the Decimat 10mm is specified in Robust Detail-compliant floor constructions for both E-FC (floating concrete screed) and E-FT (floating timber platform) floor types. When used as part of a recognised Robust Detail build-up, pre-completion acoustic testing is not required — the Robust Details Handbook certifies the build-up as deemed-to-satisfy Part E.
Key acoustic standards referenced in Part E compliance documentation
- BS EN ISO 717-2 — Rating of impact sound insulation in buildings and of building elements
- ISO 9052-1 — Acoustics — determination of dynamic stiffness (materials used under floating floors)
- BS 8233:2014 — Guidance on sound insulation and noise reduction for buildings
- Robust Details Handbook (E-FC and E-FT series) — Pre-approved floor constructions deemed to satisfy Part E
10mm vs 3mm vs 5mm: Head-to-Head Comparison
| Property | 3mm Rubber | 5mm Rubber | 10mm Decimat |
|---|---|---|---|
| ΔLw (impact reduction) | ~17–18 dB | ~20–21 dB | 23–28 dB |
| Part E suitable | Domestic only | Check build-up | Yes (in compliant build-up) |
| UFH compatible | Yes | Yes | Yes |
| Suitable floor types | All | All | All (see below) |
| Floor height increase | 3mm | 5mm | 10mm |
| Specification context | Standard domestic | Timber frame, flats | Conversions, Part E-critical |
| Thermal resistance (approx) | 0.05 m²K/W | 0.08 m²K/W | 0.15 m²K/W |
Key takeaway: 3mm and 5mm are the right specification for the majority of domestic projects. Specify 10mm when you need maximum ΔLw — typically because Part E applies, the floor construction has limited inherent isolation, or an acoustic consultant has specified a high underlay performance requirement.
Floor Height Consideration
10mm acoustic underlay raises the finished floor level by 10mm. This must be accounted for in:
- Door clearances: Door bottoms must clear the finished floor surface. A 10mm underlay plus 8–12mm flooring = 18–22mm floor build-up to allow for. Budget for door trimming or new threshold strips.
- Skirting board reveal: If existing skirting boards are retained, the gap at the floor level will be reduced or eliminated. Consider skirting extensions or replacement skirting.
- Step heights at room transitions: Where 10mm underlay abuts areas with no underlay (e.g. bathrooms with tiled floors at slab level), a smooth transition threshold is required to avoid a trip hazard.
- Services penetrations: Underfloor heating pipe centres and manifold heights must allow for the 10mm uplift at floor level.
Applications by Building Type
| Building Type | Recommended Thickness | Reason |
|---|---|---|
| Detached house (domestic) | 3mm | No Part E; comfort specification |
| Semi-detached / terraced (domestic) | 3mm | Party wall only; internal floors not separating floors |
| Maisonette (domestic) | 5mm | Shared vertical separating floor |
| Flat (new-build timber frame) | 10mm | Part E applies; lightweight construction needs max ΔLw |
| Flat (new-build concrete frame) | 5mm or 10mm | Part E applies; concrete provides mass — 5mm may suffice in compliant build-up |
| House converted to flats | 10mm | Part E (conversion standard); existing construction rarely provides sufficient isolation |
| Commercial to residential conversion | 10mm | Part E; often high noise environment requiring maximum performance |
| Hotel / serviced apartments | 10mm | Comfort standard exceeds Part E; 10mm specified by acoustic consultants |
| Student accommodation | 10mm | High footfall; Part E; value from maximum underlay performance |
Installation Guide for 10mm Acoustic Underlay
10mm rubber acoustic underlay is installed using the same floating-floor method as thinner rubber underlays, with a few additional considerations for its greater thickness:
- Prepare the subfloor: Must be clean, dry, and level to within 3mm in 2m. 10mm underlay accommodates minor undulation but should not be used to bridge structural defects. DPM may be required on ground-bearing concrete slabs.
- Plan for floor height increase: Mark doors, skirting boards, and threshold positions before laying. Allow for trim or replacement as required.
- Unroll and acclimatise: Allow the underlay to relax at room temperature for 30 minutes before cutting. 10mm rubber can be firm to unroll in cold conditions.
- Butt joints tightly: Do not overlap. Stagger joints so they do not align with floating floor board joints. Tape joints with self-adhesive tape on concrete; staple at 300mm centres on timber subfloors.
- Cut with a sharp blade: A heavy-duty utility knife with a new blade cuts 10mm rubber cleanly. Score deeply, then bend the sheet to snap. Alternatively, cut with a circular saw fitted with a rubber-cutting blade.
- Install the floating floor layer: Proceed with your click-lock laminate, engineered wood, or floating timber platform (for E-FT Robust Detail) on top of the laid underlay. Maintain the manufacturer's expansion gap.
Frequently Asked Questions
Is 10mm the thickest acoustic underlay available?
For rubber acoustic underlay in standard floating floor applications, 10mm is the practical maximum. Thicker layers create stability issues for floating floor boards (excessive flex under load) and become impractical for door clearances. Where greater total acoustic mass is required, this is typically achieved through the floor deck construction (additional boarding layers, concrete screed mass) rather than by increasing underlay thickness alone.
Can 10mm acoustic underlay be used under carpet?
It can, but 10mm is rarely specified under carpet due to the significant floor height increase. SilentCloud FFR at 5mm delivers excellent acoustic performance under carpet with less practical impact. 10mm Decimat is primarily specified in hard floor build-ups (laminate, engineered wood, floating timber platform) where Part E compliance is required.
Will 10mm underlay make the floor feel springy?
High-quality 10mm rubber underlay should not create a noticeably springy feel underfoot. The high density of rubber means the dynamic stiffness is sufficient to support foot loads without excessive deflection. If the floor feels springy, check that the floor boards are adequately stiff for the span — underlay stiffness should not be reduced to compensate for an inadequate floor deck.
How much does 10mm acoustic underlay cost per m²?
Decimat 10mm is priced at a premium over standard 3mm or 5mm rubber underlays, reflecting the greater material content and acoustic performance. However, in the context of a Part E compliance project, the cost of 10mm underlay is minor relative to the cost of acoustic testing failure, remedial floor construction, or a delay to practical completion. Specifying correctly first time is always the lower total cost.
Does 10mm underlay affect the tog value for UFH?
Yes — 10mm rubber underlay has a higher thermal resistance than 3mm or 5mm (approximately 0.15 m²K/W versus 0.05 m²K/W for 3mm). This is still within the limits of most UFH system designs, but the floor covering manufacturer's total tog limit for the complete build-up must be checked. Most laminate and engineered wood suppliers specify a maximum of 0.15 m²K/W for the complete build-up — meaning the 10mm underlay alone reaches that limit, leaving no budget for the floor covering itself. In UFH applications with a Part E requirement, discuss the specification with the UFH system designer and the acoustic consultant to agree a build-up that satisfies both requirements.
Browse our full acoustic underlay UK range including 3mm, 5mm, and 10mm Decimat rubber acoustic underlays.
