External masonry walls

6.1.5Acoustic resistance

External walls adjacent to separating walls shall be designed to resist flanking sound transmission.

Lateral restraint by buttressing wall

Acceptable levels of sound reduction between homes may be achieved by:

  • the inner leaf of an external cavity wall having sufficient density
  • sealing air paths, particularly at junctions between the masonry cavity and separating elements
  • allowing appropriate spacing between the openings in external walls
  • structural members not transferring across or breaching separating walls.

The density of external walls and the position of openings adjacent to separating walls should be in accordance with Building Regulations and, where relevant, an assessment which complies with Technical Requirement R3. Refer to the Robust Details Handbook for the specification of separating wall and floor constructions and their associated flanking walls.

Where different block materials are used e.g. aggregate separating wall with aircrete inner leaf, differential drying and cracking can occur, so it is important that the separating wall goes through (and not up to) the inner leaf.