What is RAAC?

Autoclaved aerated concrete was first developed in Sweden in the 1920s and was mainly used for the construction of lightweight thermal blocks. The reinforced version, RAAC, was subsequently introduced and widely used in the United Kingdom from around the 1950s.

RAAC is a lightweight cementitious building material.  Containing no coarse aggregate, the constituent materials are aerated rather than being solid, making it much lighter than ‘traditional’ reinforced concrete. Being lighter, cheaper and easier to work with than traditional concrete, RAAC was widely used from 1950s until the mid-1980s, in the form of wall panels or roof planks, in the construction of government estate buildings, including hospitals and schools/educational institutions.

However, while RAAC is considerably lighter and easier to work with than traditional concrete, it is also weaker and therefore may have a much shorter design life.

Issues

In the 1990s structural deficiencies in RAAC began to become apparent. During this period, the Building Research Establishment (BRE) undertook a number of inspections of school roofs and in BRE Information Paper IP10/96reported concerns regarding excessive deflection and cracking in RAAC roofing planks and corrosion to reinforcements. Following this, the widespread use of RAAC in the UK stopped amid concerns over its structural performance and life expectancy.

Issues with RAAC have therefore been known since at least the 1990s. These issues have been further compounded by cases such as the Edinburgh School masonry collapse in 2016, where part of the outer skin of a cavity wall fell onto an area used by pupils and other pedestrians (fortunately there was nobody in the vicinity at the time) and in 2018, a school roof in Kent collapsed just 24 hours after first showing signs of structural distress.

A report by the Standing Committee on Structural Safety (SCOSS) in 2019 warned that the material was inherently “much weaker” than traditional concrete. In September 2022, Local Government Association (LGA) issued a Safety Briefing Notice to all Property Leaders stating that “RAAC is now life-expired and liable to collapse”.

Current Position

The issues regarding RAAC have been well known for some time and the life expectancy of buildings containing RAAC will have expired some time ago. However, it appears that under investment in the government estate and a lack of remedial action means that there remains a large number of at-risk buildings in the public estate.

In May 2023, five major hospitals and three Scottish Police buildings have been found to contain RAAC and are part of a re-development plan.

Recently, the Department for Education (DfE) has carried out urgent check of 600 schools in England identified as being at possible risk of structural collapse and according to a report by the National Audit Office, RAAC has been confirmed in at least 65 schools, of which 24 require urgent remedial work. Earlier this month, DfE told four schools in Essex and the north-east to close after RAAC was found in the ceilings of their buildings.

Commentary

Concerns regarding the use or presence of RAAC in buildings has been known for over 30 years. The Government’s inquiry, which was only focused on school buildings, has now expanded to the identification and remediation of RAAC in the wider government and public estate.

As Matt Byatt, the president of the Institution of Structural Engineers, said RAAC could be present in “office blocks, sports facilities, high street stores and hospitality buildings. We only know where it is when it has been found. But until someone is looking for it, they wouldn’t know it’s there.”

While the government inquiry should now identify all government estate properties affected, what remedials will be required and how these will be funded remains unknown.  Likewise, the impact on private property is not known.

If RAAC is painted or otherwise concealed, it might be more difficult to easily identify and there may well be more affected properties waiting to be discovered.

Given that the widespread use of RAAC ended in the 1990’s, it is likely that limitation (even under the Defective Premises Act 1972’s new 30-year period, if applicable) is likely to have expired.  Therefore, original designers and contractors (and their professional indemnity insurers) are likely to escape any potential claims.

However, surveyors and/or those designing or working on refurbishment or re-development of buildings built from the 1950s to 1990s maybe at greater risk if RAAC is present in a structural capacity and not correctly identified.  To the extent that professional indemnity insurance policies provide cover for RAAC related claims, insurers may seek to tighten exclusions for RAAC from professional indemnity cover.

This article first appeared on Beale & Co's website