The recent news reporting’s have brought the problems associated with reinforced autoclaved aerated concrete (RAAC) into conversations of all, with experts reporting on the materials’ limited lifespan.

But what is RAAC? Our Structural Engineering Director, Luke Darwin, explains all you need to know about the material and how Building Design Northern can help.

What is RAAC?

Reinforced autoclaved aerated concrete, abbreviated to RAAC, is an alternative, lightweight form of concrete regularly used in the construction of public and private buildings.

The material was favourable in building projects between the 1950s and mid 1990s due to its lightweight nature making it easier to install and quicker to manufacture. It can be found in flat roofing, floors and walls.

With a ¼ density of traditional reinforced concrete, RAAC has an aerated, ‘bubbly’ texture – often compared to an aero chocolate bar.

Why is RAAC considered a safety risk?

The structural behaviour of RAAC differs significantly from traditional reinforced concrete, with the material’s susceptible structural failure down to moisture entering its air pockets.

If water enters the air pockets, any rebar reinforcing RAAC can rust, decay and ultimately weaken, causing panels to fail and fall.

Due to this, RAAC is typically coated with another material, such as bitumen on roofing panels, but this can also degrade over time.

How can Building Design Northern help?

With a team of Charted Structural Engineers, BDN have been reviewing and surveying properties for such concrete for a number of years and continue to receive a large number of enquiries on the material.

If you have identified RAAC elements, or suspect they might have been installed in your building and would like to discuss further, please contact us on 0191 535 6189 / hello@bdnltd.com and we will be happy to provide specialist guidance as to how we can assist.