Reinforced Autoclaved Aerated Concrete (RAAC) is an aerated, lightweight concrete based material which does not contain aggregate unlike conventional concrete. It was generally used in construction between the 1950s and 1990s as a cost-effective, lightweight material with good thermal properties.

Whilst concerns regarding RAAC have been voiced since the 1990s, the collapse of a roof in a primary school in Kent in 2018 set alarm bells ringing which resulted in a more widespread awareness campaign about the material than during previous years.

Much of the focus since has been on school buildings with the Department for Education (DfE) being rightly particularly alert to the situation. RAAC has been discovered across many other public buildings, such as hospitals and council buildings, and even private dwellings.

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