Internal Walls: Party Walls

The closed cell structure of H+H aircrete gives it excellent sound insulation properties relative to its weight and party walls built of aircrete will easily pass the requirements of Building Regulations Approved Document E.  H+H aircrete has been successfully used in cavity separating – or party – walls for many years.  The closed cell structure of H+H aircrete gives it excellent sound insulation properties relative to its weight and party walls built of aircrete will easily pass the requirements of Building Regulations Approved Document E.

Sound transmission via flanking walls – walls that adjoin the party wall, generally external load-bearing walls – can cause problems.  However, where the flanking walls are also built of aircrete, the inherent sound insulation characteristics of the material ensure the sound transmission via flanking walls is also minimized.  Sample wall specifications are registered with Robust Details, meaning that Part E compliance can be met using either Pre Completion Testing (PCT) or Robust Detail methods for both houses and flats or apartments.

Heat loss through party walls was a focus of the 2010 revision to Part L of the Building Regulations in 2010. This revision focused attention on thermal by-pass (where heat is channeled through clear cavities of party walls) as well as heat losses at junctions with the external fabric of the building (thermal bridges).

Thermal by-pass can be eliminated by ensuring the cavities are filled with insulation and effective edge sealing is put in place.

Thermal bridging can be significantly reduced by using aircrete with its enhanced thermal resistance compared to dense blocks.  When aircrete is used for party walls in conjunction with aircrete inner leaves of external walls, heat losses at thermal bridges can be reduced by around 50%.  Our factsheet Benefits of H+H aircrete for separating walls gives more detailed information on calculating the thermal bridge effect. Benefits of H+H aircrete for separating walls