Identifying Reinforced Autoclaved Aerated Concrete

RAAC is the much shorter way of saying Reinforced Autoclaved Aerated Concrete. RAAC has been making headlines in the last 6 months. But why? What’s so bad about it? And more importantly for people looking after public sector buildings, how do you identify it?

What Is RAAC?

RAAC was a commonly used building material in the 1950s right up to the 1990s. It’s a lightweight form of reinforced concrete that is made into panels or planks, which were often used to construct roofs and walls. RAAC was used in many different types of buildings, but it’s mainly found in public buildings like schools, hospitals, sports halls and court buildings. There are some cases of it being found in residential properties too, but it’s rare.

RAAC has had a lot of publicity in the last few years, especially after the tragedy at Grenfell Tower. While that was caused by polyethylene cladding, it shone a light on the potentially unsafe construction materials still present in many buildings. Including RAAC – which has been known to collapse suddenly with little or no warning. You can see our videos here for more information on why RAAC might be a problem.

How Do I Identify It?

RAAC panels are usually found on flat roofs, but they can also be found in pitched roofs, walls and even floors. They are normally a light grey or white colour, with a smooth underside. The inside of the planks will look bubbly – in fact, people often say they look like an Aero bar!

Finding RAAC can be challenging, as it can look the same as pre-cast concrete, or it’s often hidden above false ceilings. That’s one of the main reasons you need someone with professional knowledge to survey and check for RAAC if you suspect it’s in your building.

It’s important that if you notice any cracking, sagging or other damage to the panels, you bring in a Chartered Building Surveyor to help you right away. After all, RAAC doesn’t often give warning signs before it collapses.

If my Building has RAAC, Does it Need to be Demolished?

It depends. Not all buildings with RAAC need to be torn down and re-built. In fact, in some cases there might be very little benefit to doing anything. As long as a regular schedule of inspections is put into place, some buildings can carry on with RAAC in place.

However, if the RAAC is found to be deficient or structurally inadequate, repairs will need to be made. This is usually in the form of reinforcing the plank bearings, or adding in more edge support. Repairs like this may be a cheaper option and could cause less disturbance to the building and its occupants. If the reinforcement is compromised by something like corrosion or long-term water ingress, then there’s a bigger risk of failure. This is when you may need to demolish and reconstruct the building or parts of it.

So What Should I do?

The good news is, unless the building was constructed (or extended) between 1950-1990, there is a significantly lower risk.

If you aren’t sure about the construction of the building, or don’t have enough information, then the first step is to do a visual inspection of the building. You can either do this yourself (see our videos for guides on how to identify RAAC), or bring in a structural engineer or surveyor to help you. If you think you’ve identified RAAC in your building, you need to get professional support right away.

A qualified Building Surveyor or Structural Engineer with experience in RAAC will be able to confirm the presence of RAAC, even if it’s been hidden by other finishes. They can also assess its condition, likelihood of failure, and recommend specialist testing if they think it’s needed. They’ll also advise you if remedial works are needed, and what the extent of those works is likely to be. If they decide the property needs a more detailed inspection, this will have to be done carefully. RAAC may be covered with other harmful materials like asbestos, which may be harmful if disturbed.

At Harrison Clarke, we have a team of qualified Building Surveyors who can support you with RAAC issues. We have a wealth of experience in identifying and assessing properties for RAAC, as well as advising on what steps should be taken next. If you’d like to know more about what we do and how we can help you, just get in touch by phone on 023 8155 0051, or email us at

We also have a range of videos talking through various aspects of the Party Wall process. You can access them via our website or our YouTube channel

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Discover something you would like to know more about?

Paul Badham, associate director and building surveyor at Harrison Clarke chartered surveyors.

About the author

Paul Badham,
BSc (Hons) MSc PGDipSurv MRICS

Associate Director

Paul joined the team at Harrison Clarke in 2021, having previously worked with Daniells Harrison Chartered Surveyors, Vivid Housing and First Wessex Property Services. Paul first started surveying in 2008, becoming a Chartered Building Surveyor in 2015. 

Paul brings experience from his previous career in shipping, and has a degree in Shipping Operations, as well as a Post Graduate Diploma in Surveying. Paul is an RICS Registered Expert Witness and is experienced in technical due diligence, dilapidations, party wall, and contract administration.