How to Identify RAAC Concrete

In the last few months, RAAC concrete has made major headline news throughout the UK, as many schools and public buildings have recently discovered major structural stability issues.

In fact, the discovery of the flaws of RAAC concrete has been such a concern that numerous schools have had to close completely, until the issue can be rectified.

This article is designed to provide a simple outline of what RAAC concrete is, what risks it causes, and how to identify it in a building.

However, if you do think that your building might have RAAC Concrete present, or if you’re noticing any of the issues listed below, you should speak to your local authority immediately.

What is RAAC concrete, and why can it be unsafe?

RAAC stands for Reinforced Autoclaved Aerated Concrete. It is an extremely lightweight type of concrete, with a distinct aerated texture (which looks like the inside of an Aero chocolate bar).

These properties are enhanced further by the fact that RAAC concrete doesn’t contain coarse aggregates.

RAAC concrete was widely used in construction projects, particularly for public buildings (like hospitals and schools) in the 1960s-1980s. It was popular due to its light weight, good thermal properties, and the fact that it could be installed quickly, easily and cheaply.

However, its unusual texture has meant that, today, RAAC concrete has been linked to major issues regarding its strength, structural stability and durability. The aeration means that RAAC concrete has a very low level of performance in these areas.

What’s more, under certain conditions, RAAC concrete can allow water to seep into it, resulting in major structural failure. Then, its strength can be reduced even further if the concrete comes into contact with polluted air for extended time periods.

The combination of these factors means that RAAC concrete has a lifespan of just 30 years – a far shorter lifespan than was initially predicted for it. As a result, you can already see RAAC concrete deteriorating in these buildings. In some extreme cases, the concrete is causing buildings to collapse unexpectedly.

What is RAAC concrete mainly used for?

RAAC concrete was used in the construction and extension of buildings (mainly public buildings) from the 1960s-1980s. If the building does not sit within this time period, then it is unlikely that RAAC concrete is present there.

It can most commonly be found in public buildings like schools and hospitals. For these buildings, RAAC concrete was mainly used for the construction of flat roofs, but it can also be found in concrete floors and walls.

How can you tell if your building has RAAC concrete issues?

The Department for Education has asked that all UK schools inspect their buildings, to see if any elements are made from RAAC concrete.

If your building was built within the time period where RAAC concrete was used, but you aren’t sure whether or not this concrete type is present, speak to a concrete specialist. They will be able to advise you, and can be called out to survey the premises.

If your building has a roof made from RAAC concrete, the most common ways to identify an issue are:

• If the roof is cracking
• If the roof is bowing
• If the roof is deflecting

If you can see any of these warning signs, you should contact your local authority and let them know immediately.

What remediation work will be needed, if RAAC concrete is causing issues?

If you think RAAC concrete may be present in your building, or you spot any of the signs detailed above, then we recommend speaking to a building surveyor or structural engineer.

They will be able to professionally survey the property, assess any risks present, and provide you with clear details about the next steps to take, ensuring the complete safety of students and staff.

Look for a company that offers ‘RAAC survey’ services, and is both fully qualified and fully accredited.

If you are concerned, you can also speak to your local authority on behalf of your school, to notify them of the situation, and receive their guidance on the best course of action.

Or, to find out more about RAAC concrete and its identification, we recommend consulting the government’s online RAAC identification guidance document.