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 2) 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 +45 dB.

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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; Dwelling houses, flats and rooms for residential purposes shall be designed and constructed in such a way that they 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.

Robust Details
Robust Details Ltd (RDL) was formed in response to the house building industry’s need for an alternative to pre-completion site testing. “Robust details” are construction solutions which only apply to separating walls and floors for new build houses and flats.

Each robust detail has its own site work checklist. They are designed to help builders ensure that the building work is carried out to robust detail specifications, they can also be used by Building Control Bodies, new home warranty providers and others. Full details on how the scheme works is available on the website www.robustdetails.com/

Rockwool Limited has been actively involved with the robust detail process, both with the House Builders Federation, house builders and Robust Details Ltd.

Rockwool currently have robust detail solutions for timber and steel separating walls.

All robust details have a significant safety margin built into the constructions so that they would be highly unlikely to fail to meet ADE requirements. All robust details must have achieved a minimum requirement (by site testing at least 30 times) a mean airborne of D_nTw + C_tr of 50dB (5dB higher
 
than ADE), with no individual value lower than 47dB, and an impact requirement which has achieved a maximum value of L_nTw of 57dB (5dB lower than ADE) with no individual value higher than 60dB.


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. Good practice detailing at the design stage, especially at key junctions, together with good workmanship will minimise this effect and optimise performance levels. Guidelines of good practice detailing at key junctions are provided throughout the new Approved document E.