Our collective
Posted December 4, 2023 | Published in Dispute resolution

The Reinforced Autoclaved Aerated Concrete crisis: to what extent will claims “RAAC up”?

The announcement by the UK government in late August 2023, days before the start of the new academic year, that over 100 schools would not be able to re-open because their buildings were unsafe brought reinforced autoclaved aerated concrete (“RAAC”) into focus in the news.  

However, there have been concerns in the structural engineering community about the ongoing durability of this lightweight form of concrete for some time, particularly since the collapse of a ceiling at a primary school in Gravesend in Kent in 2018. 

More recently, the House of Commons Public Accounts Committee has found that the government’s school rebuilding programme has become dominated by the RAAC crisis, pushing other schools, some of which have asbestos issues, to the back of the queue for funding. In a similar report on hospitals by the Committee, which found that the government is not building new ones quickly enough to replace those that will need to close due to concerns over RAAC, Dame Meg Hillier, the Committee chair, said, “The physical edifice that is the NHS is quite literally crumbling before our eyes”.

The latest news is that pantomime season may be cancelled in some towns and cities whose theatres have had to close over concerns they contain RAAC.

All of this arrives at a time when building safety is already under the spotlight following the Grenfell Tower disaster in 2017 and the introduction of the Building Safety Act (“BSA”) last year.  

In this article, we explore whether the current issues with RAAC may give rise to an increase in claims against those involved in the construction and refurbishment of buildings containing the material.

What is RAAC?

RAAC is a lightweight cementitious material. It is aerated and has no coarse aggregate. Its structural properties and behaviour are considerably different from traditional concrete. The aerated nature of RAAC means that it is very lightweight and contains air bubbles. Its appearance has been likened to the inside of an Aero chocolate bar.

RAAC was used in buildings to form roof planks, wall panels and floor planks between the 1950s and the mid-1990s in the UK. It was a more cost-effective material than traditional concrete and so was cheaper to install, which made it attractive for public sector buildings such as schools, court houses, army barracks and hospitals.  

What are the problems with it?

There are a number of things that can potentially go wrong with RAAC in its manufacture process, at the time of its original installation or during its service life. 

In terms of the manufacturing process, typical issues have included the incorrect placement and number of the internal reinforcement cages within the panel moulds. These issues can impact upon the strength of the panel1.

Issues associated with the original installation include the insufficient bearing of panels on the end of the beam, the absence of sufficient horizontal reinforcement at bearings and the cutting of panels to size and the failure to use adequate supports for cut panels.

Defects in the RAAC panels can also be caused by subsequent works undertaken to them. The installation of new services may require builders-work holes to be drilled through the panels or fixings to be applied, which can damage the panels and the reinforcement inside them. This undermines the structural integrity of the panel, particularly if insufficient or no additional support is provided.  

Other common problems include the corrosion of the reinforcement inside the panel where there has been water ingress or condensation. This is a particular risk because corrosion can be well established before there are any obvious external signs of its presence. One of the major concerns with RAAC panels, and the key reason why schools remained closed, is the propensity for them to collapse without any warning. 

Will claims against contractors and construction professionals “RAAC up”?

This is unlikely due to the passage of time since the vast majority of RAAC was installed in buildings. Structural deficiencies in RAAC first became known in the 1990s and since that time European Standards have been published to improve standards and to ensure better long-term durability. It is likely that most RAAC panels exhibiting defects were installed before the mid-1990s.  

The viability of any claims against contractors or construction professionals will depend on the underlying cause of the defect in the relevant RAAC panel and the type of building in which it was used.  

Claims arising from the original installation of RAAC panels

Claims arising from errors during the original construction process are very likely to be time barred.  For breach of contract claims, causes of action have a limitation period of six years for simple contracts or 12 years for contracts executed as deeds.  

The usual position in such claims is that the clock starts ticking for limitation purposes at practical completion. Given when RAAC was commonly installed, claims for breach of contract against contractors for errors in the original construction will almost certainly be time barred.  

Claims against construction professionals in negligence will also be time barred: the limitation period for such claims is six years from the date of the cause of action or three years from the date when the claimant knew or ought to have known about the cause of action, subject to a longstop of 15 years.  

What about the Defective Premises Act 1972?

Under the Defective Premises Act 1972 (“DPA”), a person taking on work for or in connection with a dwelling (i.e. a building used or capable of being used as a dwelling house, rather than a building used mainly for commercial or industrial purposes) owes a duty to ensure that work is done in a workmanlike or professional manner, with proper materials so that the dwelling is fit for human habitation.

The limitation period in respect of claims under the DPA has been extended by the BSA to 30 years if the cause of action accrued before 28 June 2022.

There may therefore be viable claims under the DPA relating to the original installation of RAAC panels in dwellings from late 1993 onwards, provided that the defects can be shown to render the dwelling unfit for human habitation.  

While it is possible that defective RAAC panels would meet that test (given they are potential risk to the health and safety of occupants), the extent to which RAAC panels were installed in residential accommodation is not clear. Even with the extended limitation periods brought in by the BSA, it is likely that the vast majority of claims under the DPA would still be time barred in any event. 

Claims arising from events occurring while RAAC panels are in service 

Problems with RAAC panels are often caused by refurbishment works where service penetrations are formed in existing RAAC panels. These modifications can undermine the structural integrity of RAAC panels, particularly where no additional supports are provided. 

If such further works were carried out much later than the original installation of the RAAC panels then there may be potential claims against the contractors or designers in respect of those works where limitation has not expired. Such claims may exist where it can be shown that the defects to the RAAC panels were caused by its modification during the further works.


Given the passage of time since the construction of many buildings containing RAAC, it is likely that claims relating to their original construction will be time barred. There may be some scope to bring claims under the DPA for defective RAAC panels in residential dwellings, but this will be limited to those completed after late 1993. 

While we may see an increase in potential claims for damage caused to RAAC panels during refurbishment or maintenance works to existing buildings, it is unlikely that claims will “RAAC up” more widely.

  • 1. The Institution of Structural Engineers, Reinforced Autoclaved Aerated Concrete (RAAC) Panels Investigation and Assessment, February 2022.

Add your comment

This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Enter the characters shown in the image.