What are the Part E sound insulation targets?

Part E requires separating walls between dwellings to achieve minimum DnT,w + Ctr of 45 dB (airborne). Separating floors must achieve DnT,w + Ctr of 45 dB (airborne) AND L'nT,w of 62 dB maximum (impact). These are field test values measured in the completed building. Pre-completion testing (PCT) is normally required.

What is the difference between Rw and DnT,w?

Rw is the laboratory-measured sound reduction index of a wall/floor element. DnT,w is the field-measured apparent sound insulation, which includes flanking transmission (sound travelling around the element via junctions). DnT,w is typically 5-10 dB lower than Rw. Design for Rw values 5-10 dB above the Part E target.

What is Lnw and why does it matter?

Lnw (or L'nT,w in the field) is the impact sound transmission level measuring how much impact noise (footsteps, dropping objects) passes through a floor. LOWER is better for Lnw (unlike Rw where higher is better). Part E requires L'nT,w of 62 dB or less for separating floors.

Do I need pre-completion sound testing?

Pre-completion testing (PCT) is required for new-build dwellings and conversions to demonstrate Part E compliance. The builder can avoid PCT by using Robust Details (RD) - pre-approved constructions registered with Robust Details Ltd. Each RD-registered plot pays a fee but avoids the cost and risk of on-site testing.

What is a Robust Detail?

Robust Details (RD) are pre-approved wall and floor constructions that have been tested and proven to exceed Part E requirements. Using RD means no on-site sound testing is needed. Each construction has a specific specification (masonry type, density, plaster, cavity width etc.) that must be followed exactly.

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Part E Sound Calculator — Sound Insulation Requirements

Predict airborne (Rw) and impact (Lnw) sound insulation performance of wall and floor constructions against Part E target values.

Element type

Construction type

How We Calculate This

This calculator predicts sound insulation performance based on typical UK construction types.

Airborne sound (Rw)

Predicted Rw values are based on published performance data for standard constructions. Higher Rw = better airborne sound insulation.

Impact sound (Lnw)

For floors only. Lower Lnw = better impact sound insulation. Floating floors and resilient layers significantly reduce impact transmission.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.