RAAC in homes: what you need to know about crumbling concrete

RAAC – short for Reinforced Autoclaved Aerated Concrete – has had a lasting presence in the news owing to a string of last-minute school closures and headlines about 'crumbling concrete'.

But while hundreds of public buildings are known to be affected, the impact could ultimately be far broader. Here, we provide a simple guide explaining what RAAC is, how it's been affecting schools and other public buildings and if there's a risk to your home.

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What is RAAC?

Reinforced Autoclaved Aerated Concrete was a commonly used construction material in floors, walls and roofs in public buildings made or modified between the 1950s and mid-1990s. 

It had the advantage of being lighter than conventional concrete – but this came at a cost of also being less durable. It's considered to have a lifespan of around 30 years, but it can last longer in well-maintained buildings. However, as time has passed, concerns have increased about the potential for structural failure in buildings that contain panels (or 'planks') of the material. 

In August 2023, the Department for Education issued new guidance that any educational buildings with confirmed RAAC should no longer be open without mitigations in place. By October 2024 - when the Government stopped publishing figures on RAAC found in buildings - 237 schools and 60 hospitals had reportedly been affected.     

Has RAAC been found in homes?

RAAC was most commonly used in public buildings with flat roofs, such as schools, colleges and office blocks.

While it wasn't used widely in homes, there have been recent reports of RAAC uncovered in some social housing – and also in flats that were converted from office blocks or other kinds of public buildings.

Unfortunately, the full extent to which RAAC has been used in the private sector isn't definitively known.

How do I find out if there's RAAC in my home?

If you own or manage a building and suspect RAAC may have been used in its construction, The Royal Institute of Chartered Surveyors (RICS) advises:

• Note that RAAC planks were used from the mid 1950s until the early 1990s, so buildings (or extensions) built before or after this period are unlikely to be affected.
• Ask the local authority whether any similar buildings to yours in the area are known to have RAAC roof or floor planks.
• Check any records about the construction to see if RAAC is mentioned. But be aware that RAAC may not be mentioned even when it was used. Note that certain product names such as Siporex, Durox, Celcon, Hebel and Ytong are indicators of RAAC.
• If you do not know the construction type of a roof but it could be RAAC planks, then the roof should be inspected by a suitably qualified and appropriately experienced professional, such as a RICS chartered building surveyor or chartered structural engineer, who is experienced with this type of construction. You can use Which? Trusted Traders to find a reliable surveyor near you:

What should I do if there is RAAC in my home?

If you identify RAAC in your home, consult a qualified professional to advise you on the appropriate remedial measures to take. You can find a surveyor through the RICS website, or Which? Trusted Traders. 

Check that any professional you use is a member of a regulated processional body such as RICS and/or the Institution of Structural Engineers.

Try to keep the home dry, as moisture can exacerbate instability issues. Opening the windows or investing in a dehumidifier can help.

Read how to stop condensation for further advice on keeping your home dry.

Will any repairs be covered by home insurance?

Most buildings affected by RAAC are public or commercial properties. However, there have been reports of some homeowners facing remedial costs of tens of thousands of pounds where the cement was found to have been used in the construction of their house.

Unfortunately, home insurance is highly unlikely to cover costs associated with dealing with RAAC, as home insurance policies aren't designed to deal with flaws in the property's construction. A spokesperson from the Association of British Insurers told us: 

'We appreciate that discovering RAAC within your property can be incredibly distressing. However, domestic buildings insurance policies are generally designed to cover damaged from named perils such as storms, floods, subsidence or damage from theft. They're not intended to cover design or build defects, or to replace construction materials that are gradually deteriorating over time. So, the replacement of RAAC is not likely to be covered. 

'If you're a homeowner with cover in place, you should still be able to claim on your insurance policy if your property suffers damage from named perils or theft. If you have been made aware that there is RAAC in your building, you should contact your insurer to let them know.'

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