Current spotlight – Reinforced Autoclaved Aerated Concrete (“RAAC”)

The current spotlight on the use of Reinforced Autoclaved Aerated Concrete (“RAAC”) started with concerns raised in relation to schools and the subsequent guidance on mitigation measures announced by the Department for Education at the end of August 2023. Despite the focus on schools, the use of RAAC as a construction material in the post-war period was not limited to schools or public sector buildings and, therefore, it is incumbent on all property owners and estate managers to consider the issue of RAAC and the steps which may be required. What is RAAC and why is its use a risk? RAAC is a lightweight form of pre-cast concrete which is reinforced with metal and was used because it was cheaper, quicker to produce and considered easier to install than standard reinforced concrete. It was made in factories using fine aggregate chemicals (rather than coarse aggregate), which creates gas bubbles within it. This method of construction makes it porous and permeable meaning that water ingress can cause the steel reinforcements within it to corrode and also provides it with a lower compressive strength. RAAC was most commonly used in the production of light weight masonry blocks and structural units such as
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