What is it?

A week or so ago, most people had never heard of reinforced autoclaved aerated concrete, or RAAC. However, the Government’s recent decision to close all English school buildings constructed using RAAC and the subsequent political and media firestorm that ensued have shone a light on this widely used, yet relatively unknown material. The furore has also raised some difficult questions for public authorities, owner occupiers and others that may have RAAC in their buildings.

RAAC was used widely from the 1950s to the mid-1990s (principally to make roof and wall planks) due to its low cost, good fire resistance and thermal insulation properties. However, in the mid-1980s evidence began to emerge that older RAAC was susceptible to sudden collapse and that the porosity of the material allowed water to seep in, rusting reinforcing bars and leading the concrete itself to sag and crack, sometimes with catastrophic consequences.

Although the problems of RAAC have been known for decades, it wasn’t until the roof of the staff room at Singlewell Primary School in Kent collapsed with little warning in 2018 that the issues of RAAC were brought to the fore. In August 2023, the Health and Safety Executive ("HSE") announced that “RAAC is now life-expired. It is liable to collapse with little or no notice”.

Of course, RAAC was not just used in schools. Hospitals, prisons, courts, and other public and private sector buildings such as office blocks and theatres were all constructed using RAAC over most of the second half of the 20th century. As a result, there could be tens of thousands of buildings that will require some form of remedial work.

In this blog post, we look at what actions should be taken if you are concerned about the possibility that your building might contain RAAC. In our view, there are four key steps: Identification, Mitigation, Remediation, and Recovery (some of which may happen in parallel).


The first step is to identify whether there is RAAC in the building. In August, the Department for Education (“DfE”) released identification guidance to help authorities understand how to identify RAAC. Initially, someone with responsibility for building/ estate management should either review the building themselves or instruct a surveyor to do so (depending on experience).

When deciding what steps to take when RAAC is a potential risk, responsible parties should, at all times, consider their obligations under health and safety legislation.


If the presence of RAAC is confirmed, the next step is to mitigate the risk. The most suitable response will depend on a number of factors.

For schools in England, the current advice from DfE is to vacate areas that are known to contain RAAC unless or until suitable mitigation is in place.

In an interview with the New Civil Engineer, University of Loughborough professor of construction engineering and materials, Chris Goodier, outlined the three main strategies available when RAAC planks are detected in a building:

  • Do nothing, provided the RAAC is safe;
  • Implement strengthening, such as adding structural and load bearing support;
  • Fully replace the roof or other structure containing RAAC.

Building owners will need to carefully consider all of the available information, taking technical expert advice as required, to consider the mitigation steps required in each case to protect users of the building, comply with health and safety obligations and to safeguard the asset.


Where RAAC is found to be present in a building, remediation will, at some point, be required. The extent of and speed of any such remediation will depend on the facts in each case.

The potential presence of asbestos in RAAC planks may complicate the inspection and remediation processes. This toxic material was also widely used as the same time as RAAC and is a serious hazard when disturbed. Care will therefore have to be taken when evaluating whether buildings contain RAAC and when carrying out inspection and/or remedial works.

Remediation may also be complicated by a lack of capacity in the construction sector. Julian De Voy, technical director at risk mitigation consultancy HKA, noted that "It is likely the demand for [RAAC remediation] services could outstrip the available skill set in the short term, and we could see both public and private organisations waiting some time for remedial works to be completed.” The sheer number of RAAC planks could also add to remediation time-frames. Steve McSorley, director at construction consultancy Perega, warned there could be in excess of 100,000 RAAC planks in the UK. Replacing all of these would “take time”. This, in turn, could have a longer term impact on the available use and occupation of affected buildings.


The number of buildings that contain RAAC mean that demolishing and rebuilding all of them would cost multiple billions. In just the education sector, replacing one 1950s block in each of the 572 schools with a potential RAAC problem would cost around £3.1bn according to DfE estimates published in 2022. This doesn’t account for the possibility that each school may need to replace more than one block, or the knock-on costs associated with temporary alternative accommodation and other related costs. Extrapolate these costs to other public and private sector buildings and it is clear that the cost of RAAC remediation works is likely to be significant.    

At present, the focus is, rightly, on identification, mitigation and remediation of RAAC, but we are likely to see building owners also consider their routes to recovery.

As most buildings containing RAAC were built pre-1980, it may be difficult to claim remediation costs from the original construction company due to contractual/statutory limitation periods. Many of the original contractors may also have gone out of business in the intervening decades in any case.

It may be that the Government intervenes to (as it did for the remediation of fire safety defects under the recently introduced Building Safety Act 2022), however, any such legislative action is likely to be a long way off. The factual circumstances are quite different when considering RAAC and the appetite for Government involvement to assist the private sector may be limited.  

Claiming entities may look to recover from their insurers, subject to specific policy terms. PFI companies and/or FM providers may also be required to rectify remediate RAAC at their own cost depending on the terms of their contracts.

Careful assessment of any available routes to recovery will be important and this is likely to be a developing area of law, and a cause of disputes, in the years to come.  

Concluding thoughts

RAAC in buildings is not an issue that will go away when the news cycle moves on. Remediation is likely to take many years and cost billions of pounds. Whilst this will be daunting for those responsible for buildings that may contain RAAC, the issue needs to be proactively addressed. Early identification is key. Mitigation can then be put in place before the problem is rectified. Whilst it is not yet clear who will be best placed to foot the bill, or what support Government will provide, things will become clearer as the extent of the problem is revealed.

Burges Salmon’s specialist building safety team is monitoring the developments with RAAC and can advise and support clients on each of the Identification, Mitigation, Remediation and Recovery stages.

This post was written by Richard Adams and George Bridge