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Commercial Question

RAAC: what you need to know

updated on 12 December 2023


What legal dilemmas are posed by RAAC and 'crumbling' school roofs?


The public was made aware of the problem of 'crumbling concrete', or reinforced autoclave aerated concrete (RAAC), when there was widespread reporting of schools being unable to open for the new autumn term. The subsequent assessment of the condition of other public buildings, shops, offices and the like, means that those in the construction, insurance and legal sectors have new issues to consider including the potential for claims.

What’s RAAC?

RAAC was extensively used in the construction of walls, floors and roofs in the UK from the 1950s to the mid-1990s, as a cheaper, quicker alternative to concrete. The material, which contains air bubbles resembling an 'Aero' chocolate bar, has a lifespan of around 30 years and is susceptible to decay if not properly maintained or sealed from moisture. The flat roofs common in public buildings have been particularly affected due to exposure to rainfall accruing and pooling on their surfaces. It’s forced some organisations to move completely out of their premises into safer, temporary buildings. These recent events have highlighted that the RAAC used in the UK is approaching its design life expectancy.

Who does it affect?

A significant number of public buildings were built with RAAC, such as schools, hospitals and prisons, with some of these being sold into the private sector and repurposed into, for example, offices.  Other buildings in the private sector, such as some shopping malls, are equally at risk. Of particular concern is that when RAAC does fail, it carries a high risk of structural collapse with little warning. As a result, professionals in the construction and insurance sector are eager to understand the liabilities that may arise from the potentially wide impact of this problem.

An immediate task for many will be the carrying out of risk assessments to establish the presence and condition of any RAAC. This might begin with a desktop analysis, then a visual inspection and potentially an intrusive survey. If RAAC is present, mitigation and remediation plans will be necessary. Contracts may impose obligations on a number of entities, including building owners, landlords, tenants and employers.

Problems with legal action

One of the first legal issues to determine is who’s responsible for dealing with the mitigation and remediation of RAAC. For freehold properties, that might be quite simple, but the issue becomes more complex if the interest in the property is leasehold. It might also be the case that recent works on a building disturbed the RAAC or led to water ingress making it degrade. Perhaps a condition survey prior to a purchase of a building should’ve identified the RAAC.

The original use of RAAC in buildings may not be seen as defective, given it was perceived as an adequate material at the time and the problems have emerged later due to lack of maintenance or reaching the end of its lifecycle. This is in contrast to the issue of cladding, where much material didn’t comply with the regulations at the time. Buildings insurance likely won't cover damage caused by gradual deterioration or inherent defects, so some building owners may then consider professional negligence claims against construction or property professionals.

Legal action in contract and tort may be time-barred. The Limitation Act 1980 has a default position of six or 12 years to bring a claim (with an extended limitation period in negligence, which is subject to a 15-year long-stop). Given that RAAC fell out of use in the 1990s, this route doesn’t seem likely to succeed.

Claims relating to residential buildings could potentially be brought under Section 1 of the Defective Premises Act 1972. The new Building Safety Act 2022 (BSA) extends the limitation period to 30 years retrospectively for claims accruing before 28 June 2022 and to 15 years for claims accruing after 28 June 2022. However, the passage of time may mean that relevant entities involved in the original construction no longer exist, and documents may have been lost or destroyed. The BSA allows courts to dismiss claims where the retrospective extension of the limitation period infringes on the defendant's right to a fair trial.

It could be that those carrying out subsequent repair works, such as maintenance contractors, surveyors and building managers, assume responsibility for the condition of the RAAC. However, RAAC was often used with other materials and can be difficult to detect visibly. Accordingly, invasive testing would in some circumstances be needed to identify RAAC, and those carrying out subsequent repair works may highlight the practicality of this in relation to any potential liability.


The full scope of the legal implications of RAAC are still unclear and the situation is fluid. However, those in the construction and insurance sectors will be attuned to any developments and the types of claim that are ultimately presented. The potential route(s) of significant litigation remains under consideration but there’s little doubt the courts will start to see some initial claims soon. In the meantime, those responsible for buildings containing RAAC will be assessing their contracts and putting in plans to mitigate against damage and liability.

Harry Wells is a trainee solicitor in Womble Bond Dickinson’s London office.