What does RAAC mean for building owners?

Advice on the ongoing RAAC crisis, with an expert perspective from our sister company Martech’s concrete expert Jerry Nichols.

Unsafe concrete, particularly in schools, continues to grab headlines. But behind the news stories is the human reality of building owners protecting their assets and livelihoods. Now enough time has passed for stakeholders to critically assess their options and make more informed decisions.

Here, concrete expert, Jerry Nichols, MD of Bellrock company Martech, shares his advice on what you need to know.

What is RAAC?

Reinforced autoclaved aerated concrete (RAAC) is made of cement, lime, water, sand, and aluminium filings, reinforced with small-diameter rebars. It typically comes in plank-like panels, usually 600mm wide and anywhere up to 6 metres in length.

The material is relatively soft; you can easily mark it with a nail or screwdriver. On closer inspection, you’ll see the air pockets formed by the aluminium filings reacting with the cement, causing hydrogen gas bubbles. These evaporate, giving RAAC its distinctive honeycomb appearance.

“RAAC only ever had an intended service life of less than 30 years. In practice, this means that all RAAC currently installed is either approaching or past its safe operating condition.”

RAAC was lightweight, cheap, and easy to install, with good thermal properties. For these reasons, it was used widely in public sector construction from the 1930s to 1990s, particularly after the 50s.

Why does RAAC pose a safety risk?

RAAC only ever had an intended service life of less than 30 years. In practice, this means that all RAAC currently installed is either approaching or past its safe operating condition. Several failures have been reported since 2018, all in flat roofs where the material was most commonly used.

Worryingly, these failures have been known to happen with no prior visible warning. Jerry is keen to emphasise this aspect of the issue: “In normal concrete, you can see the signs over a longer period of time. Unless there’s something seriously wrong, there’s a period where you can see cracks appear.

With RAAC, because it’s honeycombed, you can get a leak and it’ll soak that water up like a sponge. You may see no outward signs of it doing so. Or the steel can corrode and, because of the aerated concrete, you get nothing happening at the surface… until it fails.”

Where was RAAC most often used?

Recent news has focused on RAAC being used in schools, where it undoubtedly saw widespread use. But it was also used in other public sector buildings like offices, hospitals, leisure centres, student accommodation, and theatres.

Could RAAC affect other types of buildings?

Despite mostly being used in the public sector, it’s possible that other types of building might contain RAAC.

In Jerry’s experience, there are factors clouding the issue of which buildings might contain RAAC: “For one thing, there are scaremongers out there. I saw someone suggesting it’ll be found in tower blocks next, and in my experience you don’t get it in those type of buildings.

“But elsewhere, you see buildings which have changed hands and gone from public to private use. Maintenance records and instructions can get lost over time. People revert to treating these buildings like normal ones, not knowing they need to replace the planks.

“And of course, there was covid. The last RAAC advisory note was 2019, which is when things went wrong. A lot of places are still catching up from that.”

What do UK regulations say about RAAC?

Responsibility falls to individual building owners if they suspect their properties may contain RAAC. Failing to protect the health, safety, and welfare of those using your building is a criminal offence. Ignoring the risk posed by RAAC could translate into hefty fines and bad press for public sector organisations.

It’s worth noting that liability under UK Health and Safety legislation is triggered merely by the risk of harm. No injury or actual building failure needs to occur for a building owner to be potentially prosecuted.

In August 2003, the Department for Education released full guidelines for those responsible for state-funded education sites.

RAAC and Asbestos

Given the overlap between periods when RAAC and asbestos were both used in building, many properties contain both. Asbestos is subject to its own extensive scrutiny and legislation due to the serious risk it poses to health.

Bear in mind that inspections for RAAC often find asbestos as well. You may be legally obliged to remove the asbestos before or alongside remedial works related to RAAC. Plan and budget accordingly.

How to find out if you have RAAC in your building?

Building owners can conduct an initial RAAC assessment on their property themselves, according to Jerry: “First thing is really simple; how old is the building? You can rule out anything built before 1930 or after about 1995.

Next, do a walk round and look for other areas you can rule out, timber roofs for example. You’re narrowing the property down to areas you can’t see or aren’t sure about.”

What to do if you find RAAC in your property?

If you’re responsible for a statefunded education site where RAAC is suspected or confirmed, you must immediately inform the Department for Education.

At Bellrock, we can provide a building surveyor in the first instance.

We’ll be able to assess whether RAAC is actually present in your building, before bringing in our dedicated concrete surveyors.

If needed, we can then recommend options for longterm management and project manage remedial work.

Some concrete might need to be replaced immediately. Other areas might require a steady, managed approach. In any scenario, we’ll be able to recommend a course of action to help you protect your building as effectively as possible.