Behind the Headlines – Reinforced Autoclaved Aerated Concrete

What’s happening?

This year there has been concerns raised nationally around the presence of Reinforced Autoclaved Aerated Concrete (RAAC) in school buildings - leading to the closure of certain schools across the country.

There has been significant press coverage nationally on this and we thought it would be useful to set out the position in Orkney – and provide some information about RAAC.

The key point to make clear from the start is that we have carried out a survey and there is no RAAC present in our buildings – and therefore no risk.

What is RAAC?

Reinforced Autoclaved Aerated Concrete (RAAC) is a lightweight form of concrete. RAAC ‘panels’ were precast offsite and used for flat and pitched roofs, eaves, floors and walls within building construction.

Although called “concrete” it is very different from traditional concrete and, because of the way in which it was made, much weaker. The useful life of RAAC has been estimated to be around 30 years.

Where is RAAC commonly found?

RAAC was used in schools, colleges, and other building construction from the 1950s until the mid-1990s.

Why is there a potential risk?

In the 1990s, several bodies recognised structural deficiencies apparent in RAAC panels. It was found that performance was poor with cracking, excessive displacements and durability all raised as concerns.
In the mid-1990s, the Building Research Establishment (BRE) undertook a number of inspections of school roofs. It was recommended that school owners should identify and inspect RAAC panel construction to determine deterioration and put in place management strategies.

In December 2018, the Department for Education (DfE) and the Local Government Association (LGA) made building owners aware of a recent building component failure in a property constructed using RAAC. In May 2019, a further alert was raised to emphasise potential risks from such construction and highlighted the failure of a RAAC panel roof construction within an operational school

What’s the situation in Orkney – what’s the Council doing about this?

Following a review and survey work, it can be confirmed that RAAC is not present in any Orkney Islands Council property. Apart from exceptional cases, Orkney uses traditional construction techniques which excludes the types of property components that use RAAC.

However, we’ve taken a ‘belts and braces approach’ and gone a step further, inspecting any properties whose construction techniques could have utilised RAAC. In such cases, further analysis was done, with on-site inspections being carried out if RAAC could not be entirely ruled out.

Westray Community School for example has some non-traditional construction but we were able to immediately identify that it did not have RAAC

We also carried out additional inspections for RAAC at Stenness Primary School and the former Papdale Halls of Residence. Again these inspections found that there was no RAAC