UK Schools Swap RAAC for Timber Amid Crumbling Concrete Crisis

New research suggests the reinforced autoclaved aerated concrete crisis should be treated like asbestos.

Thu 07 Sep 23


More than 100 schools across the UK are scrambling to make arrangements after being told facilities were at high risk of collapse due to ‘crumbling concrete.’

A new report has flagged up to 572 schools and colleges across the UK where the crumbling concrete might be present. 

The BBC reports that the risk of injury or death from a building collapse was “very likely and critical” by the National Audit Office (NAO) after a June report highlighted concerns for school buildings that still contained the faulty material.

Wood Central understand that the concerns revolve around a ‘bubbling material’ known as RAAC – or reinforced autoclaved aerated concrete – used primarily on flat roofing, floors and walls between the 1950s and 1990s.

The material is said to be a cheaper alternative to standard concrete; however, its short lifespan means its use in permanent buildings has caused problems.

In response, the UK Government is working to rapidly replace the crumbling material with timber joints – with experts leading calls for monitoring to be extended to cover thousands of additional buildings which used the material.

Led by Professor Chris Goodier, a team from Loughborough University is concerned that the threat caused by RAAC is higher than previously thought.

The team started looking into the issue two years ago on behalf of the National Health Service and found three main factors that were not fully taken into account by risk assessors:

  • RAAC soaks up water like a sponge and increases the load on the building if it is exposed to rainwater.
  • Stress tests showed it becomes 25% weaker when wet.
  • An analysis under a microscope showed that cracks can appear around the steel rods running through the RAAC

Although the material has been used for decades, the team claims there has been little research into what happens when it ages.

In 1994, concerns about the risks associated with the material in public buildings began to appear in research, with excessive cracking and corrosion found in roof planks in 1996.

At the time, a government report concluded that “there is no evidence so far to suggest that RAAC planks pose a safety hazard to building users.” 

In 1999, building owners with pre-1980 RAAC were told to get them inspected. The advice came from a body set up to spot risks to building safety – the Standing Committee on Structural Safety (SCOSS).

The Loughborough researchers now use the term “living with RAAC” and say the material must be dealt with, like the asbestos crisis of the 1980s and 1990s.

According to Professor Chris Goodier, most affected buildings were not dangerous but should be inspected “just in case.”

“We’ve suddenly discovered that a certain proportion of our building stock is not as good as we thought it was,” Professor Goodier said.

“It’s a small proportion, but we have millions of buildings – even if it’s just one per cent of 10 million, that’s 100,000.”

As well as government buildings, including hospitals, courts and prisons, an unknown number of private sector offices and warehouses were also potentially exposed because they contained RAAC.

‘But the public sector is the easy bit because the government has control over that and knows where it is,” Professor Goodier said. 

“But when you move to the private sector – you are mainly looking at the 1960s, 1970s offices, factories and warehouses and possibly some housing where you may not know who owns it.”

In the longer term, the team said a new approach is needed, with the UK government regularly inspecting and managing potentially tens of thousands of buildings, according to Prof Sergio Cavalaro from the team.

“Buildings that were not inspected will now need to be inspected. We need to intensify these inspections. But that will be a challenge because so many buildings need inspections. So we may lack the qualified people to do it timely,” he said.

To make matters worse, these problems aren’t apparent until the material breaks.

“Collapse after something looks like it’s going to collapse is one thing; it’s collapse without warning is the worry,” Professor Goodier said.

A UK government spokesperson said it had been guided by expert advice.

 “That professional advice from experts on RAAC has evolved, from advice in the 1990s that RAAC did not pose a safety hazard to more recent advice on identifying and assessing structural adequacy,” the spokesperson said.


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