External solid walls in severe exposure conditions

An external solid wall in conditions of "severe exposure" should be constructed with – (a) brickwork or stonework at least 328 mm thick, dense aggregate concrete blockwork at least 250 mm thick, or lightweight aggregate or aerated autoclaved concrete blockwork at least 215 mm thick; or (b) brickwork or blockwork which should be rendered or be given protection equivalent to render. The mortar used in the construction of the walls should be in accordance with the guidance given in BS 988-2 and the render should be designed, prepared and applied in accordance with the guidance given in BS EN 13914-1. Premixed and proprietary renders should be used in accordance with manufacturer's instructions.