What is RAAC?

Evaluating the risk and a 4-step approach to identification and remediation.

Whether it is schools, hospitals or other public sector buildings, the topic of RAAC planks is one that continues to cause concerns and challenges for building owners. Most recently there have been report of structural failures with RAAC planks and in some instances the collapse of roof buildings.

Industry guidance and information has been published by the Standing Committee on Structural Safety, Department for Education and also the Institution of Structural Engineers. In all instances, the need to identify whether RAAC materials are present in buildings is vitally important.

Survey Solutions have worked on a number of projects to identify the presence of RAAC and completed measured surveys to inform building owners of any potential issues with the RAAC planks.

Typically, this would be providing highly accurate data on the levels of flanking or bowing of each individual plank.

This technical article sets out all you need to know about RAAC planks and the support you can receive from Survey Solutions and their industry partners.

RAAC explained

Reinforced Autoclaved Aerated Concrete (RAAC), is a material that may have been used in the construction of buildings including schools, hospitals and other public sector buildings. This type of concrete differs from traditionally dense concrete and has been used as part of construction projects because of the material’s lightweight thermal properties. RAAC is most commonly used for flat roof structures but has also been used in the construction of walls and floors.

Is my building likely to have RAAC planks?

RAAC was a material used a lot in the construction of schools, hospitals and other buildings primarily between the mid-1960s to mid-1980s. Whilst it has been used when constructing floors and walls it’s primarily found in roof structures due to its physical properties being less strong than traditional concrete. Over time, this could cause issues with the structural integrity of the roofs it is used in.

It is not always possible to say that RAAC would not be in other types of buildings such as commercial buildings or other public sector buildings. Buildings or extensions to buildings pre or post-dating the period of 1960 to 1980 are unlikely to be impacted though if unsure a visual check should be carried out as the first step.

What needs to be done?

In line with the guidance from the Department for Education published in February 2021, the priority action for building owners is to establish whether RAAC is present in the building. Whilst the guidance suggests that schools built post the mid-1980s are less likely to have RAAC present, it is still advised to get this checked. This can often be done visually by a specialist surveyor. If there is RAAC present, it is recommended to engage with a structural engineer to inform the next steps.

Credit: Local Government Association

How can we help?

Having worked on a number of schools and hospitals, Survey Solutions is well placed to help any building owners with this process. We have shown below a simple four step process that we would follow should you ask us to complete a RAAC plank survey.

STEP 1 – If you are worried your building may contain RAAC material, we can visit your site and provide expert guidance on its presence.

Depending on the size of the building and the number of locations where we think RAAC may be present, we would expect the initial inspection to take a maximum of one working day. For larger buildings this may extend into a second day, but this would be made known to you when we review the plans of the building. From this we would look to get a technical report out to you within two working weeks which provides a review of our visit and recommendation for next steps.

Whilst completing the initial survey there may be times when we need to gain access to parts of the roof structure to ascertain whether RAAC is present. At all times we will look to work around the footfall and operations of the building and keep disruption to an absolute minimum.

Each building can present its own challenges with our surveyors using their expertise to solve solutions as they find them. In some cases, we have needed to access planks concealed by suspended ceiling tiles, in others we have had to work around the issue of solid fixed ceilings. This included using an inverted mini prism to gain access to the planks.

STEP 2 – If RAAC is present, we can provide a technical report and recommendations for next steps. This may include surveying the RAAC planks to identify any structural issues which a Structural Engineer would then use as part of a remedial works proposal

STEP 3 – We work with many of the UK’s leading structural engineers and can use these relationships to develop a project team that will provide a plan of remedial works.

STEP 4 – If required we can set up regular survey visits to your site, providing ongoing accurate and reliable monitoring data on the performance of the RAAC planks. This would tell you whether the condition of the planks has worsened over time.

Using Survey Solutions not only provides expertise with this type of work, but we also cover the entire UK with a network of nine offices. With over 160 engineering surveyors, our teams are on hand to attend site quickly and help provide the information and survey data you need for your RAAC plank survey.

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