Technical Notes 2023, Issue 150 - Reinforced Autoclaved Aerated Concrete

This technical note provides Members with information about reinforced autoclaved aerated concrete, the status of the Council’s inspection work and actions taken to date.

1. Reinforced autoclaved aerated concrete (RAAC) is a lightweight construction material that was used in the construction of some public buildings between the 1950s and 1990s.  It was used mostly in flat roofing, but also in some pitched roofs, floors and walls.  It was quicker to produce, easier to install, and cheaper than standard concrete. Despite its name, it is very different to traditional concrete. It is aerated, or ‘bubbly’, and is therefore less durable than traditional concrete.
    
2. RAAC can be susceptible to failure when exposed to moisture. The ‘bubbles’ can allow water to enter the material.  This moisture can also cause decay in any reinforcement steel (‘rebar’) present in the material.  In February 2022, a report was published by Institute of Structural Engineers RAAC Group following an incident in England in 2018 and an initial safety alert in 2019.  Guidance was published by the group in April 2023.  There have been two recent collapses of RAAC in schools in England recently, which has triggered the UK Government’s recent action and subsequent media coverage.
    
3. Work to establish the presence or otherwise of RAAC across the learning estate was completed in late 2022 and concluded that the Council’s learning estate did not contain RAAC.  This work was reviewed in June 2023 with the conclusion consistent with the 2022 review.
    
4. Following the recent request for a further review to be completed, officers are now in a position to confirm conclusively that there is no RAAC present within the Council’s learning estate.  
    
5. Work remains ongoing to establish the presence of RAAC within the Operational (Corporate) and Non-Operational estates, however assessments and surveys completed to date have not uncovered the presence of RAAC within those assets. One (1) asset remains to be full assessed within the Operational estate, with a further nine (9) in the process of being surveyed across the non-operational estate.  An update on the outcome of those surveys will be provided in early course.
    
6. A desktop analysis of the Council’s Housing stock is ongoing to establish whether surveys will be necessary.  Further updates will follow once that work concludes.