RAAC is in the news, but how widespread is it? We have recently seen the issues in schools with reinforced aerated autoclave concrete (RAAC), but this material was popular for many years, with modernist architects looking to move away from traditional materials.

While the news has focussed on the use and impact of RAAC in schools, it is widely acknowledged that this material is present in other buildings, such as hospitals and courts. At Lysander, we know its use is more widespread because we have seen it present in many buildings, including hotels. We have been inspecting and reporting on the situation for some time and have a wealth of experience advising on mitigating the effects.

RAAC, as with all materials, has a design life. Undoubtedly, this has been exceeded because it was used until the mid-1970s. However, it doesn’t mean it has to be replaced, although that might be the last resort. In much the same way as we do with asbestos-based products, it can be managed by regular inspection and monitoring. The significant issue is that a building owner, landlord or tenant must be aware of the existence and herein lies the challenge, as many do not know or have never needed to know. Lysander can support clients with this because we know what to look for and how to identify the material.

One of the challenges faced is that RAAC was predominantly used in flat roofs as the decking where a lightweight solution was required, usually a simple building or extension where plant and equipment was not envisaged. In more recent years, retrofitted plant, like solar panels, air conditioning or telecommunications equipment, has been added, changing the dynamic of the roof. This manifests itself as a catastrophic failure, not progressive and can at best, be a surprise if the building owner is not prepared.

What is still not clear is how this story will develop. RAAC could join the ever-changing list of deleterious or harmful materials or become an inherent defect – no one knows. We recommend being prepared and starting the process with an initial visual inspection and further material testing if appropriate.

Don’t hesitate to contact the Building Surveying team at Lysander to discuss any concerns or requirements you may have.