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The dangers of RAAC: What schools need to know

By: Kelly Bellerson

The Department for Education has urged schools to check their buildings following an increase in reports of structural failures and collapsed roofs.

The production of RAAC was stopped in 1982 amidst structural fears and has not been used in the UK since. However, RAAC is still present in public sector buildings today.

Reports of structural failures, problem planks, and even collapsed roofs, have begun to surface and The Department of Education has urged schools to check their buildings.

What is RAAC?

Reinforced autoclaved aerated concrete (RAAC) is a ‘bubbly’ form of concrete that was used in construction projects between the 1960s and 1980s.

Differing from the traditional denser concrete, RAAC has been used for most flat roof structures because of its lightweight and thermal properties, however, it has on occasion been found in floors and walls.

It is not as strong as other forms of concrete and where RAAC is commonly identified in public sector buildings, such as schools, this could cause problems with significant consequences.

How to spot RAAC

Ceiling panels may need to be removed in order to identify RAAC. Loft access could also be required if the roof is structurally hidden.

Sometimes spanning on to masonry walls or between steel beams, it’s possible for RAAC to be found on pitched or sloped roofs too.

Unless heavily painted or coated, RAAC is crumbly when touched, with visible bubbles and an open texture.

The panels are either grey or white with arc-shaped stripes across the face, typically sporting a slight chamfer on each edge, measuring 600mm wide and 2.4m long – but this can vary.

The dangers of RAAC

Compared to traditional types of concrete RAAC corrodes easily, has a lower compressive strength, is susceptible to all types of weather conditions, and has a life expectancy of little more than 30 years.

Hairline cracking within RAAC planks has led to excessive structural deterioration and deflections in service with little to no warning signs.

Schools constructed between the 1960s and 1980s are now over the 30-year RAAC threshold, meaning the possibility of damage is extremely high.

RAAC threatens the integrity of the rest of the building, which can be costly to fix. Additionally, the possibility of a collapsed roof, walls, or floor puts everybody in the building at high risk of injury.

What to do if you have RAAC

The Department for Education has requested schools check their buildings as a matter of urgency.

Firstly, see if any of the buildings were constructed between the 1960s and 1980s. Look out for ‘reinforced autoclaved aerated concrete’ or the term ‘RAAC’ on any original building designs/modifications paperwork.

Brands ‘Siporex’ and ‘Durox’ may appear on the design paperwork where RAAC is present.
Before inspecting the roof, you will need to identify how accessible it is, taking into consideration any health and safety issues.

Consult your school’s asbestos register to ensure the ceiling is clear before inspection. RAAC panels may need to be broken into by an asbestos specialist where there may be the possibility of asbestos debris.

If you cannot inspect the roof yourself or would like a professional to evaluate it, you should contact a chartered building surveyor or certified contractor. They will undertake a risk assessment and plan how to carry out any works safely.

If RAAC planks are identified, they will need to be removed. A structural engineer will be able to do this for you.

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