A separating wall is defined as a wall that separates adjoining dwelling houses, flats or rooms used for residential purposes.

The Approved Document E requirement for new build separating walls (ADE Section 4) is subject to airborne sound regulations. It introduces performance criteria for separating walls. The minimum value for airborne sound insulation is D_nTw + C_tr=43 dB (or greater).

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Section E1 of Part E document deals with the protection against sound from other parts of the building and adjoining buildings; this section gives guidance on conversion work for dwelling houses and flats formed by 'material change of use' to provide reasonable resistance to sound from other parts of the building and from adjoining buildings.

Soundpro solutions have been designed to give insulation against airborne sound. The resistance to airborne sound of timber walls depends on the mass per unit area of the leaves, the cavity width, frame material and the absorption in the cavity between the leaves.

Pre-completion site testing is also required. Alternately adopting Robust details do not require site testing.

Flanking Sound
A major cause of reduced acoustic performance in separating walls is Flanking paths via the surrounding structure rather than a direct path through the wall. Special attention needs to be given to situations where flanking walls or floors are continuous across separating walls or floors as a result of the conversion work. In such instances, additional treatments may be required to control flanking transmission along these continuous elements.

Corridors walls and doors
The separating walls described in this section should be used between dwelling-houses or flats formed by ‘material change of use’ and corridors in order to control flanking transmission and provide the required sound insulation. However, it is likely that the sound insulation will be reduced by the presence of a door.

Ensure that any door has good perimeter sealing and has a minimum mass of 25 kg/m² or minimum sound reduction of Rw 29 dB. The door should also satisfy the Requirements of Building Regulation Part B - Fire Safety.
Note: Pre-completion site testing is not required for walls which contain doors.