Reinforced autoclaved aerated concrete (RAAC) is a lightweight material that was used between the 1950s and 1990s, predominantly in the construction of flat roof sections but also in floors and walls. This material has a limited lifespan of around 30 years and has been found to be susceptible to structural failure particularly when exposed to moisture. RAAC panels were often coated with bitumen or similar moisture retardant substances but the concrete beneath this coating layer can still be compromised and the Health and Safety Executive