by Trevor Rushton, Chairman

Originally published by Public Sector Focus

Fortunately, collapses in buildings are rare, but when they do happen, the effects on life and the consequential events can be catastrophic. Failures associated with RAAC (Reinforced Aerated Autoclaved Concrete) planks are now becoming well known; property owners and managers need to take action to determine whether their buildings are at risk and whether and to what extent mitigation measures are needed.  

Typically RAAC planks can be found in buildings such as schools, hospitals, primary care, infrastructure (such as pumping houses) libraries and the like. Examples have been found in shopping centres and commercial buildings predominantly constructed between 1960-1980. 

Unlike normal concrete, RAAC is a much softer material made by combining fine aggregate and chemical compounds to create a foaming reaction followed by curing to create the finished product. The material is characterised by a prominent bubble structure like an aerated chocolate bar. Essentially, autoclaved aerated concrete is used to make lightweight building blocks in common use throughout the UK but reinforced planks are much larger structural units often up to around 2.4m long and 600mm wide incorporating light gauge steel reinforcement. The planks were commonly used for flat roofs but occasionally found applications in walls or tiled mansard structures.