A number of school building owners have already taken steps to identify reinforced autoclaved aerated concrete. For those that have not, this guide explains how to carry out an initial check to determine whether further advice/action is necessary
Reinforced autoclaved aerated concrete (RAAC) is a lightweight, ‘bubbly’ form of concrete that was commonly used in school and other buildings from the mid-1960s to the mid-1980s. RAAC is mainly found in roofs, and occasionally in floors and walls. RAAC is less strong than traditional concrete; there have been problems as a result which could have significant consequences.
Establishing whether your buildings might contain RAAC
By following the steps outlined below you should be able to establish whether your school buildings could contain RAAC.
Step one: were any of the school buildings constructed between the mid-1960s and mid-1980s?
If yes, or not sure, go to step two.
If no, it is unlikely that your buildings will contain RAAC, but you may wish to carry out a visual inspection to confirm this.
Step two: can you obtain the original design drawings and details of subsequent modifications?
If yes, do they contain terms such as ‘RAAC’, ‘reinforced autoclaved aerated concrete’, ‘aerated concrete’, or the brands ‘Siporex’ or ‘Durox’? If the answer is yes, it is likely your school buildings contain RAAC.
If the answer to this is no, go to step three.
Step three: carry out a visual inspection of the roof to see if the roof contains RAAC
Step four: after carrying out step three, does the roof contain RAAC?
If yes or not sure, arrange a survey and assessment by a structural engineer.
If no, no further action required.
What to do if you suspect there is RAAC present
Before inspecting a roof, you (or an appropriately qualified person) should make a preliminary visit to identify any access and safety issues, understand the extent of work involved, and undertake a risk assessment and plan the work; the height of the roof is an important safety consideration.
During the preliminary visit you should consider the following questions:
Can the underside of the roof be seen and/or accessed easily and clearly? If yes, take photos of the roof to email to a qualified professional for an expert opinion.
Is the roof less than 3m above the floor and covered with a suspended ceiling? If yes, it may be possible to access the roof by using a ladder.
What type of suspended ceiling is present?
Is the roof so high that access equipment will be needed to see the surface clearly? If yes, engage an appropriately qualified person to access the roof.
In order to carry out a visual inspection you will need to look up at the roof from the floor below and take some photos. Expand the photos to get a close-up view of the roof surface and compare with the photos in the FIS Guide, or email them to a structural engineer for an expert opinion. If you can access a concrete surface, tap it with a hammer to identify whether it is normal, heavyweight concrete or lightweight RAAC. Normal concrete sounds solid and hard when tapped; RAAC feels much softer. If the panels do not have a coating, try to push a small screwdriver or nail into the material; a screwdriver will not penetrate normal concrete, but will make a small hole in RAAC.
If there is a coating, do not make a hole – the coating may contain asbestos. Do not go up onto the roof, particularly if there is no safe means of access, such as a staircase, or there are no guardrails around the roof perimeter.
If there is a suspended ceiling, and the panels are relatively light and can be lifted up and moved to one side to expose the ceiling void, follow the FIS Guide. Use a torch to view the underside of the roof and take photos. Do not touch or disturb any of the materials in the ceiling void.
Further information
Further information about RAAC, and guidance on undertaking investigations and inspections, is available in the following documents:
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