The concrete crisis: what’s being done to address RAAC risks?

Posted on: 13 September, 2023

What is RAAC, the building material at the centre of the UK concrete crisis, and what is the UK government doing to address safety risks?

Last month, just days before the start of the autumn term in England, over 100 schools were ordered to shut over safety concerns. What’s followed has been a PR crisis for the UK government, as schools scramble to make alternative arrangements and a series of disastrous oversights come to light in the news.

At the centre of the concrete crisis is the use of RAAC – a lightweight alternative to reinforced concrete. The government has published a list of 147 schools known to contain this material, but many fear the true number of buildings at risk could be far higher.

So what brought RAAC to public attention? Why do buildings made of RAAC pose a safety risk? And what can built environment professionals and businesses do to make sure their buildings aren’t at risk?

What is RAAC?

Reinforced autoclaved aerated concrete (RAAC) was invented in Sweden in 1930 and emerged in the mid-1950s as an alternative to reinforced concrete. As its full name suggests, RAAC is full of air bubbles that help to reduce its density, making it a cheaper and lighter form of concrete.

RAAC became particularly popular in Europe, as well as Turkey and Japan, often being used in the construction of walls, flooring, and roofing. RAAC was most commonly used in public sector buildings, such as schools and hospitals, but ultimately felt out of favour in the UK in the 90s amid safety concerns. Despite this, it’s still used across Europe to this day.

Why is RAAC a safety risk?

While RAAC is cheap to produce and light, its composition ultimately makes it less durable than other types of concrete. Its loading capacity is also significantly less than generic concrete, and its deterioration can be accelerated by exposure to water from heavy rain or floods.

Loading capacity is the maximum amount of weight a structure or material can take before it fails.

According to gov.wales, RAAC has a lifespan of around 30 years. While this can be lengthened by proper repairs and maintenance to protect it adequately from water, RAAC can fall without warning or any sign of deterioration, posing an enormous risk to a building’s occupants – including school children. In the aftermath of the crisis, RAAC has been discovered in public buildings, including university campuses, theatres and airports.

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When did concerns about RAAC first emerge?

RAAC may have only hit headlines in August, but concerns over the longevity and structural integrity of this material have been raised since as early as the 1980s.

The weakness and limitations of RAAC were first observed around 30-40 years after their adoption in the UK. These concerns emerged again more recently when, in July 2018, a ceiling collapsed at Singlewell Primary School, Gravesend. This incident was linked to RAAC.

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At this point, the government began monitoring the condition of buildings in the public sector containing RAAC, and the Department for Education released guidance to schools for how to identify and address RAAC.

In August of 2022, the UK Government Property Agency stated that RAAC “is now life-expired and liable to collapse with little or no notice”. The pressure grew in 2023, as more and more RAAC panels began to collapse in school buildings. All of this led to the announcement from the government last month.

Teachers have criticised the timing of this order, being so close to the beginning of the autumn term, while Education Secretary Gillian Keegan has been vocally critical of schools for failing to communicate with the government and complete RAAC surveys sent in March 2022.

What’s being done about RAAC?

After the order was sent to schools to close in August, the government has worked to increase the number of temporary buildings in a coordinated effort with contractors and utility companies. £1.8 billion in capital funding has been committed to ensure schools stay operational, while the School Rebuilding Programme – a plan to transform over 500 schools over the next decade – has been launched.

For the buildings that have so far been identified, RAAC can collapse without warning, so while efforts can be made to repair and maintain it, removing it entirely is the safest option. Chancellor Jeremy Hunt has promised the government will “spend what it takes” to make schools safe.

However, with RAAC being discovered in more and more buildings and the budget for repairs and maintenance already tight, it may be a long time until this crisis is fully addressed.

Are you a building surveyor? Have you been impacted by the RAAC crisis? We want to hear your thoughts. Get in touch with us at press@ucem.ac.uk.