05 Sep, 2023

Reinforced Autoclaved Aerated Concrete (RAAC): An Overview, Challenges, and Solutions

Safety, durability, and sustainability are paramount when constructing schools and other important buildings. Reinforced Autoclaved Aerated Concrete (RAAC) gained popularity as a type of concrete used in the construction of public buildings from the 1950s to the mid 1980s.

In this blog post, we will explore what RAAC is, identify some of the problems associated with its use, and discuss what schools and other buildings should do if they suspect RAAC was used in their construction.

What is Reinforced Autoclaved Aerated Concrete (RAAC)?

Reinforced Autoclaved Aerated Concrete, commonly known as RAAC, is a lightweight precast concrete material that has been used in various construction applications for decades. RAAC was created by mixing fine aggregates and chemicals, which react to form small gas bubbles throughout the mixture. These gas bubbles create a highly porous and lightweight concrete, often referred to as “aerated” concrete.

RAAC was known for its excellent insulation properties, fire resistance, and relatively low environmental impact compared to traditional concrete. It was also seen as easy to work with, making it a preferred choice for builders looking to reduce construction time and costs.

Problems Associated with RAAC

Despite its advantages, RAAC has faced challenges, particularly concerning its long-term structural integrity and potential health risks:

Durability Concerns: RAAC is susceptible to deterioration over time, especially in harsh environmental conditions. This can lead to structural issues, compromising the safety and longevity of buildings constructed with RAAC, as highlighted in recent news.

Moisture and Mould: RAAC’s high porosity makes it more prone to moisture absorption. If not adequately protected or sealed, this has led to mould growth.

Asbestos Contamination: In some cases, older RAAC materials may contain asbestos, a highly hazardous substance known to cause serious health issues. Buildings constructed with asbestos containing RAAC may require asbestos remediation.

What Schools Should Do If RAAC Was Used

If a school or any other building believes that RAAC was used in its construction, it’s essential to take proactive steps to address potential issues:

Identify: With an approximate working lifespan of 30 years, there is a need to identify and remediate properties where RAAC is found. The Government has issued a new guidance on how RAAC can be identified.

Consult Experts: Engage with experienced building surveyors or structural engineers who are knowledgeable about RAAC and can assess the condition of the material in your building. They can conduct structural evaluations, moisture tests, and asbestos surveys if necessary.

Inform DfE: Log onto the RAAC Questionnaire and inform the Department for Education that you have identified RAAC in your education estate.

Asbestos Testing: If there’s suspicion of asbestos containing RAAC, conduct asbestos testing to determine if the material poses a health risk. If asbestos is found, follow appropriate asbestos removal and abatement procedures.


Schools and other buildings should proactively be investigated by consulting experts, conducting necessary tests, and implementing maintenance and renovation strategies.

At CTS our Structural Investigation team can support your assessment of your estate with both Visual Surveys and Intrusive Structural Surveys.


Contact a member of the team to discuss your requirements.