Reinforced Autoclaved Aerated Concrete planks  (RAACs)
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Reinforced Autoclaved Aerated Concrete planks (RAACs)

Date published

Reinforced autoclaved aerated concrete (RAAC) is a form of lightweight concrete sometimes referred to as panels. It was used primarily in roof planks of some public buildings built between the mid-1950s and mid-1990s.


Why was this study group formed?

Following failures in reinforced autoclaved aerated concrete (RAAC) planks/panels, SCOSS issued an alert along with reports of failures to CROSS. This led to the Institution setting up this study group to provide a place for information and guidance on RAAC. You do not need to be a member of the Institution in order to join the study group - it is open to all.
Join the group to receive updates

Managing structures with RAACs

We have established key action to support building owners/ managers.

The following are suggested steps that building owners/ managers who are responsible for the safety of buildings should follow. This will enable building owners/ managers to address any issues relating to reinforced autoclaved aerated concrete (RAAC) that may be present in their structures:

  1. Identification – Not all buildings built between 1950 to mid-90s will have RAAC. It is therefore important to establish if they are present in your building. Identification can be undertaken by an experienced estate/ maintenance manager/ or building owner. A guide has been created to enable managers of educational buildings to identify if their buildings have RAAC. However, if you are unsure then you can contact a professionally registered structural engineer or surveyor to identify if RAAC are present. To note they do not need to be an expert in RAAC to identify if the building has RAAC

  2. Assessment – Once you have established that RAAC has been used, your building will need to be assessed to understand what, if any, risk there is and if any immediate temporary remedial work is required. IStructE Chartered and Incorporated-Members would be competent to assess your structures.

  3. Solutions - Competent structural engineers will need to evaluate all the information (which will include a detailed site inspection) and propose any remedial works to be completed.

Competent IStructE Chartered and Incorporated Members will have experience of assessing structures, using their engineering judgement and providing solutions for different types of buildings. All IStructE Chartered and Incorporated Members have signed up to the Institutions code of conduct, which requires that they operate within their area of competence and that they maintain their competence through continuing professional development, such as keeping up to date on the latest guidance on RAACs.

IStructE Resources

Related Resources


Local Government Association         - Information on Reinforced Autoclaved Aerated Concrete (RAAC)

Health and Safety Executive (HSE)   -  Advice regarding schools and education

CROSS Report 908                             -  Failure of RAAC planks in schools

You can confidentially share your experiences on RAAC planks with CROSS


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