Reinforced autoclaved aerated concrete (RAAC) – inspect, advise, mitigate and manage

12 September 2023

Jerome Edwards, director of building surveying in the UK, shares his insights into the topic of RAAC: why it causes concerns, the need to identify whether RAAC materials are present in buildings and how to address associated issues.

What is RAAC?

RAAC, reinforced autoclaved aerated concrete, is a lightweight, bubbly form of concrete that was used primarily in roofs, but also occasionally in floors and walls.

The material has been used in public buildings across the country including schools, police stations, courts and hospitals built between the 1950s and 1990s. The true scale of the problem is unknown as it’s not possible to say that RAAC hasn’t been used in other non-public sector buildings, for example commercial office or residential properties.

RAAC is weaker and less durable than ordinary concrete, but was favoured in construction projects because of its lightweight, thermal properties. It was seen as a cheaper alternative to traditional concrete, that is quicker to produce and easier to install.

What are the concerns?

Since RAAC is less durable than traditional reinforced concrete and deteriorates over time, it is susceptible to sudden failure. It has a life expectancy of around 30 years, therefore, buildings that have not been checked are at risk of structural failure, with little or no notice.

Moreover, it is particularly susceptible to structural failure when exposed to moisture. The bubbles can allow water ingress. If that happens, any reinforcement bars within the RAAC can decay, rust and expand, so weakening the concrete.

What action needs to be taken?

The priority action for building owners/managers is to establish whether RAAC is present in their buildings.

To gain a full understanding, building owners/managers should instruct a chartered building surveyor or engineer to conduct RAAC surveys to inspect buildings to identify any areas containing RAAC so advice can be provided to manage and mitigate associated risks.

How can we help?

Our chartered building surveyors, who work throughout the UK from our network of 17 offices, will co-ordinate in depth surveys to verify the presence and condition of RAAC used in buildings. We will produce detailed reports with findings and recommendations, in line with current government guidance. We will explain the identified risks, recommending short- and long-term remediation strategies to ensure buildings are structurally sound and those occupying them are safe.

The RAAC issue needs to be continuously observed so any changes that may alter the proposed remediation strategy are quickly identified. We can arrange regular survey visits, providing ongoing monitoring data on the RAAC. This will indicate whether the condition has worsened over time.

Get in touch

If you own or manage buildings that you suspect may contain RAAC and wish to find out more about our RAAC surveying service, please contact:

Jerome Edwards
Director – Building Surveying
[email protected] 
+44 7767 625 509