What sound rating does Part E require for party walls?

Part E of the Building Regulations requires new-build party walls to achieve a minimum of 45 dB DnT,w (airborne sound insulation). For conversions (e.g. converting a house into flats), the target is 43 dB DnT,w. These are minimum values measured on site — the wall system should be designed to exceed them to account for workmanship variations and flanking transmission.

What is the difference between Rw and DnT,w?

Rw is the laboratory-measured sound reduction index of the wall system itself. DnT,w is the on-site measured value that accounts for room size, flanking paths and workmanship. DnT,w is typically 5-10 dB lower than Rw due to these real-world factors. Part E specifies minimum DnT,w values. Always select a system with a laboratory Rw at least 5-8 dB above your DnT,w target.

Which acoustic wall system is best?

It depends on your space and budget. Resilient bar with double-boarding is the most common solution for party walls, offering Rw ~55 dB in minimal thickness (~70mm added). Twin stud frames give better performance (Rw ~58 dB) but use more floor space (~200mm). Independent leaf systems achieve the highest ratings (Rw 62+ dB) but need ~120mm from the existing wall. All systems need careful sealing to prevent flanking.

Do I need acoustic mineral wool?

Yes. Mineral wool (minimum 100mm, density 10-36 kg/m³) is essential in all acoustic wall systems. It absorbs sound energy within the cavity. Without it, the cavity acts as a resonance chamber and actually amplifies certain frequencies. Use acoustic-grade mineral wool from brands like Rockwool, Knauf or Isover. Standard insulation rolls work, but denser acoustic slabs (e.g. Rockwool RWA45) perform better.

What is acoustic sealant and where do I apply it?

Acoustic sealant is a permanently flexible, non-setting mastic applied at all junctions where the plasterboard meets the floor, ceiling and adjacent walls. It seals air gaps that would otherwise allow sound to flanking around the partition. Apply a continuous bead behind the board at all perimeter edges. Standard decorator's caulk is not an adequate substitute — use a proper acoustic sealant rated for the purpose.

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Sound Rated Wall Calculator — Part E Compliance & System Selection

Select the right acoustic wall system to meet Part E sound insulation targets. Compare resilient bar, twin frame and independent leaf configurations.

Wall Length

Total wall length

Wall Height

Floor to ceiling

Sound TargetPart E minimum for new-build party walls: 45 dB

Wall SystemChoose based on target dB and available space

Board Price (optional)

Per acoustic plasterboard

Insulation Price (optional)

Per pack of mineral wool

How We Calculate This

This calculator helps you select the right acoustic wall system to meet Part E sound insulation targets and estimates the materials needed.

The approach

Select target dB → Choose system with Rw exceeding target → Calculate materials

For a Part E new-build target of 45 dB DnT,w, select a system with Rw ≥ 52 dB (allowing 5-8 dB for site factors). Resilient bar + double 15mm boards achieves Rw 55 dB.

System performance (lab Rw)

Resilient bar + 1×15mm: Rw ~48 dB
Resilient bar + 2×15mm: Rw ~55 dB
Twin stud frame: Rw ~58 dB
Independent leaf: Rw ~62 dB

Based on tested systems from British Gypsum, Knauf, and Robust Details Ltd. All values assume correct installation with acoustic sealant at all perimeters.