The sense that little in Britain works anymore has slipped into our very buildings, with hundreds, if not thousands of public buildings at risk of collapse over the use of Raac – reinforced autoclaved aerated concrete. Raac has forced the closure of more than a hundred schools alone, with the cheap construction material used between the 1950s and 1990s also found in courts, hospitals, and other public buildings.

Similar to the issue of asbestos, Raac could be present in an unknown number of buildings given how widely it was used in construction. The Health and Safety Executive said Raac is “beyond its lifespan” and may “collapse with little or no notice.”

The risks of Raac have been known since at least 1996, when a government report recommended Raac panels in visibly poor conditions be inspected every year, with those in a visibly good condition being expected every 5 years.

However in 2002, the government stated that corrosion can occur without visual indication that the panel was in poor condition, thus meaning there is a risk of sudden collapse in buildings with Raac panels which are over 20 years old. However some panels were inadequate at the time and did not meet regulation when they were installed.

While the concrete crisis is mainly contained to public buildings at present, there is a potential risk to organisations and businesses. Given the widespread use of Raac as a building material for over 40 years, there is a potential risk that businesses should understand, and mitigate the risk. 

Identifying Raac

RAAC panels are light-grey or white in appearance, the underside of the panels will appear smooth. The inside of the planks will appear bubbly, often described as looking like an Aero bar. Unlike traditional concrete, there will not be visible stones (aggregate) in the panels. 

RAAC panels are most commonly found on flat roofs, they may also be found in pitched roofs, floors or walls. 

RAAC panels are very soft. If you press a screwdriver, screw or nail into the surface of a RAAC panel you will be able to make an indentation in them. Be cautious, however. If there is a surface covering to the panels you should not try to make an indentation as the covering may contain asbestos.  

When looking directly at the structure, can you see one or more of the following? 

  • 600mm wide concrete panels (typically)
  • Distinctive V-shaped grooves at regularly spacing (normally 600mm in a floor, wall or ceiling
  • Floors, walls or ceilings that are white or light-grey (where they have not been painted) 
  • Drawings of your buildings that refer to RAAC or mention any of the following suppliers Siporex, Durox, Celcon, Hebel and Ytong 

Raac warning signs

  • Cracks in the RAAC may indicate that the structure is under stress, or that there has been damage to the material.
  • Moisture penetration or water damage can weaken the RAAC and reduce its performance. Signs of water damage may include discoloration, staining, or softness in the material.
  • Over time, RAAC may deteriorate due to exposure to weather or other environmental factors. Signs of deterioration may include flaking, spalling, or crumbling.
  • Reinforced RAAC structures may be susceptible to corrosion of the steel reinforcement over time, which can weaken the structure and cause damage.
  • If a RAAC structure is experiencing significant movement, this may indicate that there are underlying issues with the foundation or support structure.

However, Raac is at risk of collapse without any warning signs. 

Mitigating the risk

If you have identified a risk or Raac, a building surveyor or structural engineer should be engaged to examine the situation. Conduct a risk assessment if Raac is suspected in the building and contact the HSE and local authority as soon as possible. 

If Raac is found, it may need to be reinforced or removed and replaced. Site and building managers should:

  • Regularly record the condition of all buildings
  • Identify any Raac in the property
  • Ensure any Raac-identified properties are inspected by a structural engineer
  • Maintain good roof maintenance practices
  • Know if Raac is used in any building and where
  • Regularly check for visual signs of cracks, water penetration or other damage
  • Ensure all staff know how to report cracks and other maintenance issues
  • Immediately close off any part of the building where cracks or other damage appears in the building