UPDATED: Investigating, assessing, and managing reinforced autoclaved aerated concrete (RAAC) in buildings

News

This article was updated on 11 September 2023.

Recent headlines about dozens of schools in England being ordered to close has brought RAAC, or reinforced autoclaved aerated concrete, back into the spotlight, but this is an issue that has been known and discussed within the built environment and successive UK governments since at least the 1980s, and more substantially since the 1990s.

Data on the extent of the problem is limited, but a report by the National Audit Office has provided some insight on the public sector. At present, it is understood that 24 hospitals (of over 11,000) and 156 schools (of over 24,000) have been found to contain RAAC, indicating the problem is not widespread. However, the picture may of course change as more data becomes available. RAAC also exists within the private sector. As this is an evolving situation, advice may change over time. IWFM will continue to monitor the situation.

What is it?

RAAC is a material used in some buildings to form roof planks, wall panels, and sometimes floor planks, between the mid-1950s and mid-1990s.  It is a highly aerated, lightweight, concrete based material, with different material properties than conventional concrete.

Is there a potential safety concern?

In a statement issued on 1 September 2023, The Institution of Structural Engineers (IStructE) said, 'If properly designed, manufactured, in good condition and with good bearing, RAAC installations are considered safe. However, the panels can creep and deflect over time, and this can be exacerbated by water penetration. A more recent incident indicated that if they have insufficient bearing and their structural integrity is compromised, they can fracture and collapse with little or no warning.'

What is the response at Government and industry level?

The RAAC Industry Response Group was convened for the first time on Thursday 7 September, by the Construction Leadership Council (CLC) in conjunction with the Cabinet Office and other government departments. IWFM was represented during the meeting through the Building Safety Alliance and its representative, Mark Snelling.  

Who leads on the technical elements of the guidance?

IStructE is leading on the technical elements of the Industry Response Group’s response. They have shared guidance on RAAC to enable building owners or managers to manage the situation, established a RAAC working study groups, and created a list of professionally qualified structural engineers (Chartered or Incorporated Members) who have declared their experience in providing technical solutions for managing RAAC planks. 

This is a situation that remains under development. Members should monitor the IStruct page on RAAC for any potential updates to their advice.

We will continue to monitor developments in this area and publish updates when appropriate.

Who should be carrying out assessments when deciding to do a survey?

The Collaborative Reporting for Safer Structures UK (CROSS-UK), a confidential reporting system which allows professionals working in the built environment to report on fire and structural safety issues, have recently issues a report about a RAAC assessment that was carried out by persons who did not appear to have appropriate experience, potentially putting building users at risk of harm.

The Key Learning Outcomes in the report for building owners, managers, surveyors, and other persons responsible for the safety of buildings are:

• building users could be at significant risk of harm if incompetent assessments of RAAC are relied upon;
• If RAAC is suspected, an assessment should be made by a Chartered Structural or Chartered Civil Engineer familiar with the investigation and assessment of reinforced concrete structures;
• If RAAC is confirmed, a risk assessment of the building and its use is advised;
• Risk assessments should have input from an engineer with appropriate knowledge and experience of RAAC; and
• The Department for Education (DfE) publication, Reinforced autoclaved aerated concrete: estates guidance, contains advice useful when appointing an engineer to assess RAAC.

IWFM has been engaged on this issue through our work on the School Estates Working Group and we recently held a webinar on structural safety where we discussed RAAC.