The potential weakness of RAAC (Reinforced Autoclaved Aerated Concrete) was first identified in the mid-90s. It was at the end of August 2023, when the Department of Education decided to close schools that contained this material that the issue came to the attention of the wider population. The material was used in a range of buildings built between the 1950s and 1990s, but it is buildings from the 1950s,1960s and 1970s are most at risk.
What is RAAC?
Autoclaved Aerated Concrete (AAC) is concrete that is formed with an expansion agent to create a lightweight concrete full of air bubbles. This reduces the quantity of materials used and creates a product that has good thermal insulation. It is widely used in the blocks used in domestic buildings – this form of construction is perfectly safe. But in the 1950s the idea of using reinforcement in the product was developed and it was typically cast in 600 mm wide planks ( or panels) and used in roofs and walls. This is known as RAAC, and this it is the material that has suffered from sudden failures.
How do I know if my building has RAAC?
Where the panels are visible Identifying RAAC is not too difficult and the Department of Education has produced a guide that gives good advice on locating RAAC within a building. Where the structure is covered up, then finishes may need to be removed so that structure itself can be seen.
How can Structronix help?
Our Technical Director, Owen, has many years of inspecting buildings with all types of defects. He has experience of dealing with more unusual building materials and construction types. As a Chartered Structural Engineer (MIStructE) he is trained to assess and understand a wide variety of construction materials, and to apply his knowledge to new situations. The Institution of Structural Engineers have prepared specific guidance on the assessment and treatment of RAAC in buildings which provides essential state of the art knowledge on the material.
If you think that your building has RAAC then please contact us and we will assist you through the following steps: Confirm that RAAC is present with an inspection. The inspection will inform if the building should be vacated urgently, or if temporary measures can be put in place.
If RAAC is present then a detailed survey will be required, and the inspection in step 1 will inform what is required to enable suitable testing and measurements to be carried out.
A more detailed risk assessment can then be undertaken, including the need for further surveys, or if necessary, identify the need to replace/strengthen the structure.
If you have a concern about RAAC in your building, contact the Structronix team via email at office@structronix.co.uk or call us on 01256 833628.
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