by Hayley Coles, Associate

Originally published by Property Week

Reinforced aerated autoclaved concrete (RAAC) planks are now considered to be short-life materials where failure, while rare, could have disastrous consequences.

RAAC planks were first introduced into the UK in the mid-to-late 1950s and production stopped in 1982. By the 1980s, failures started occurring to RAAC planks. Where complete failure occurs, it occurs suddenly. This has brought RAAC planks greater public awareness. Property owners and managers need to take action to determine whether their buildings are at risk and what mitigation measures might be required.

RAAC is a form of steel-reinforced lightweight concrete, with a porous internal bubble-like structure. The reinforced planks are large structural units working independently, loads are not shared as with conventional concrete. Planks are up to around 2,400mm long and 600mm wide.

They can be found in many buildings including schools, hospitals, primary care facilities, infrastructure, libraries, shopping centres and commercial buildings. Most used for flat roofs, they are occasionally found in walls or tiled mansard structures.

According to the Building Research Establishment, the material has a life expectancy of around 30 years. If built to standard and kept dry, RAAC can last longer. However, rushed construction, less stringent quality control methods of the time and later re-roofing leave it vulnerable. This does not mean failure will occur beyond life expectancy, but the risk is increased.