* Autoclaved Aerated Concrete Products Association
** Building Research Establishment

There is considerable interest in the concept of a cavity party wall {separating wall) for domestic housing built with loadbearing masonry without wall ties to connect the two leaves. Such a wall would give better sound resistance than equivalent tied structures because of the omission of the ties which transmit sound vibrations between the leaves but would not comply with the current structural stability requirements of the Building Regulations. This paper describes a full scale model test comprising a 9m span, 100mm thick single leaf AAC blockwork. watt – representing one half of an untied cavity party wall, sufficient length of returns adequately to buttress this wall, a full 4.5m span timber floor borne on joist hangers on the wall and a section of roofing. The arrangement was conservative in that neither straps at the floor/wait junction, roof tiling, ceiling coverings, nor further internal partitions or buttresses, were added but strapping and tying was normal elsewhere. The floor was loaded in simple three point bending using hydraulic jacks and a Christmas tree load spreading arrangement. The structure remained serviceable (undamaged) to welt beyond the required working live load of 1.5kN/m2 and failed, by rupture of part of the floor, at 5.1kN/m2 with a factor of safety of over 3.