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Homeowners’ guide: Reinforced Autoclaved Aerated Concrete (RAAC)

Have you heard about the school closures across the country due to fears about Reinforced Autoclaved Aerated Concrete (RAAC)? Unfortunately, it's not just schools that are at risk. Find out what you need to know here.

Reinforced Autoclaved Aerated Concrete (RAAC), which is now being dubbed “crumble-prone concrete”, is the culprit behind the nationwide school closures mentioned in the news recently.

In 2019, it came to the attention of the Standing Committee on Structural Safety (SCSS) that RAAC posed a significant risk of failure, meaning it could deteriorate and collapse.

In 2022, the Office of Government Property sent a Safety Briefing Notice to property leaders reiterating this concern, stating “RAAC is now life-expired and liable to collapse.”

The serious safety implications of this realisation have caused schools to temporarily shut across the country, as RAAC was a fairly common building materials used throughout the 50s, 60s and 70s in both public and private buildings.

Currently, close to 150 schools have closed due to the “crumbling concrete crisis”, but the issue also affects an unknown number of hospitals, courts, private sector offices and warehouses, and residential buildings.

This article offers expert advice on the topic, covering everything you need to know to stay safe and protect your property, including how to fix the issue if it affects you.

What is Reinforced Autoclaved Aerated Concrete (RAAC)?

RAAC is a relatively lightweight and strong form of aerated concrete containing a mesh of reinforcing steel wires. It’s also cured in an autoclave, which is high-heat, high-pressure steam chamber.

Being relatively cheap, lighter than traditional concrete and a good thermal insulator, RAAC can sometimes be a good material to use, and it is still used in construction projects throughout the world.

However, it’s only a suitable material if properly designed, manufactured, installed and maintained.

Experts are now realising the batches built and used in the UK in the 50s, 60s, 70s and 80s aren’t as durable as initially thought, and the material is now being called “crumbly and prone to collapse.”

Reportedly, RAAC used in roofs is most likely to see the worst deterioration, as water is a main driver.

This is obviously a huge national concern, although no buildings have collapsed as of yet. Efforts are now focused on assessing buildings and taking the appropriate action to prevent what some are calling “a cladding-style scandal in the making” – referring to the tragic events at Grenfell Tower in 2017.

Is RAAC used in houses?

Yes, some houses have been constructed using RAAC. Some council housing stock constructed between the 1950s and 1980s contain RAAC, and openDemocracy has discovered that at least one council estate that’s still in use was built using RAAC.

This news is greatly concerning to landlords, who have a legal responsibility to maintain a safe living environment for their tenants.

If you’ve bought a property with this kind of background or you suspect RAAC may be contained therein for whatever reason, you should have the building/s surveyed as soon as possible.

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What are the problems with RAAC concrete?

In layman’s terms, RAAC concrete crumbles over time. Unlike traditional concrete, RAAC doesn’t contain coarse aggregates, like crushed stones and gravel, which add a great deal of strength.

The idea was to make a lighter form of concrete by combining the properties of aerated autoclave concrete with reinforced concrete. Of course, this didn’t turn out very well and we’re experiencing the consequences of the failure today.

What’s being done about the issue?

While there doesn’t seem to be any immediate danger, relevant experts are warning of likely problems in the near future, with issues like ceilings collapsing being a near certainty in some buildings.

The NHS, which has seven buildings primarily constructed from RAAC, has issued instructions requiring the removal of the unsafe material by 2030.

As seen on the news, schools are closing in response to the Department of Education’s instructions for all school buildings to be checked for RAAC, adding that they’ll offer financial support for expert guidance to be brought in.

Landlords are responsible for arranging building surveys on their properties, so if you suspect RAAC was used in any of your owned homes, or you own a council house constructed between the 50s and 80s, it might be worth speaking to a building surveyor.

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Can I tell if my building contains RAAC?

Ceiling falls through. Risk of RAAC (Reinforced Autoclaved Aerated Concrete) - image 2

Our advice to the public is not to attempt to identify whether there is RAAC in your buildings, or to assess the condition of known RAAC planks yourself.

Due to the nature of the material, defects can be difficult to identify. If you are unsure whether your building includes RAAC, then you should use a suitably qualified professional, such as an RICS chartered building surveyor or chartered structural engineer.

Regular Planned Preventative Maintenance (PPM) surveys should assist in identifying and managing potentially defective materials.

If RAAC is found, what happens?

A trained person will come and look at the important supporting part (called an “end bearing”). If that part isn’t the right size (75mm), they’ll need to take a closer look.

They might use a special tool or even a drill to poke around and find out how deep the supporting part goes into the material (RAAC) and where some extra strength (transverse reinforcement) is added.

If that extra strength is in the right place and the supporting part is within the size recommended by the people who made it (40mm-50mm), then everything should work just fine. If not, they’ll need to add extra supports and maybe do some other fixes to make sure it’s safe and works properly.

Is RAAC still being used?

Surprisingly, RAAC is still in use all over the world, as it’s not an inherently dangerous material, but it must be designed, manufactured, installed and maintained in the right way.

This, unfortunately, wasn’t the case with the batches produced and installed throughout the UK in the 50s, 60s, 70s and 80s, hence the problem we’re experiencing today.

While the use of this construction material has largely been phased out in countries like the UK and many others, modern variants have been designed to address the shortcomings of the older products, and these are in use in countries like the United States, Germany and India.

Beyond RAAC, what else should you check?

After hiring a surveyor to confirm your home or rental property is free from RAAC, it’s also worth taking advantage of the opportunity to carry out other essential checks.

Here are the most important checks for homeowners and landlords to do for safety and provide the best living environment:

The structural integrity of your property

This check would need to be completed by a Structural Engineer. They can also check other essential parts of your property, like brickwork, roofs, foundations, windows, doors and drainage systems.

It’s recommended that you complete a structural inspection every 3-5 years.

Pipes and plumbing

Plumbers can check the condition of your pipework and discover any issues with your plumbing before it becomes an issue. For example, leaking pipes can cause huge issues if left too long without repair. The worst part is that many people may not even realise they have a leaking pipe until they see discolouration on their walls or a hole in their ceiling!

It’s recommended that you get your plumbing inspected every 1-2 years. See how much it costs to hire a plumber.

Electrics and wiring

Electricians can verify the safety of your wiring, circuit breakers, outlets, switches and all other electrical components, all of which must be in safe working order.

It’s recommended that you have your electrics inspected and tested every 10 yearsCheck out the cost to hire an electrician.

Boiler

Landlords are legally required to make sure boilers are safe and functional, which they do through annual servicing. This is a great rule for homeowners to live by too!

It’s recommended that you book a boiler service once a year. Here’s how much you can expect to pay for your annual boiler service.

Gas appliances

Landlords must have gas appliances checked by a Gas Safe registered engineer annually, and this is absolutely recommended for homeowners too.

Discover what a gas safety certificate is, why it’s essential for your home, and how to find a Gas Safe registered tradesperson to certify your home today in our Gas Safe blog.

Chimneys

Be it a fully open fire, coal or wood-burning fireplace, having your chimney regularly inspected and cleaned is essential. It reduces the risk of dangerous fume emissions, prevents the risk of chimney fires, and limits any harmful pollutants entering your room.

It’s recommended that chimneys are swept at least once a year, or more regularly if it’s in constant use. Check out what a chimney sweep costs.

Why these checks matter to you

For landlords: Besides making sure your tenants are safe, these essential checks help you maximise the value of your property and keep them generating profit over the long term.

For homeowners: It keeps you, your family and home safe. Completing these regular checks and maintenance can even increase the value of your home!

Here is a detailed house maintenance cost guide to help you budget and prioritise your options.

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What others think of this article:

Hinda Aussenberg

Very useful and helpful info. Thank you

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