Earlier this month, Reinforced Autoclaved Aerated Concrete (RAAC) became front-page news as the Government advised the immediate closure of some school buildings due to safety concerns, and until remediation works were completed. The latest government data reveals a total of 174 schools and 41 buildings across 23 hospital trusts contained RAAC. Network Rail has also announced it is reviewing if RAAC is present across its estate. The full impact on the private sector is yet to be revealed.

Given the wide use of RAAC, the Government has issued guidance, along with the Health and Safety Executive (HSE) and Institution of Structural Engineers (IstructE), advising building owners and managers to take immediate action to identify if their property is impacted.

Numerous institutions and stakeholders are now taking proactive steps to inspect, assess, and remediate the potential risks posed by ageing RAAC structures. We’ve put together this guide for those looking to understand more about RAAC, what their next steps should be and why engaging a Chartered Structural Engineer is vital in addressing the issue.

What is RAAC?

RAAC is a specialised type of concrete, used in various structures, including schools, hospitals, and commercial buildings, between the 1950s and the 1990s. The material is characterised by its unique combination of reinforcement and autoclaving, a process in which it’s exposed to high pressure and temperature.

The resultant product is an aerated, lightweight, precast concrete material, known for its superior thermal insulation properties. Structures built using RAAC benefited from its lower weight in comparison to the traditional material, leading to savings in foundational works. Its inherent qualities meant that structures made with RAAC could be erected swiftly, and it became a popular choice for constructing floor and roof planks during this era.

Understanding the issue

Concerns about RAAC stem from the material’s age and inherent vulnerabilities, for example, to water ingress. These vulnerabilities can be exacerbated by manufacturing inconsistencies and construction defects. Now considered far beyond its estimated lifespan of 30 years, there is a heightened risk of structural failure. Cases have been reported where RAAC planks have unexpectedly collapsed, which has led to increasing safety concerns among building owners, managers, and the general public.

In this alert from 2019, The Standing Committee on Structural Safety (SCOSS)  issued guidance about RAAC, following reports of failures submitted to the Collaborative Reporting for Safer Structures UK (CROSS), a UK body established as a forum for raising structural safety issues.

In 2018, the Local Government Association (LGA) and the Department for Education (DfE), contacted all schools to advise that inspections should be undertaken, particularly in the case of flat roofs. These concerns escalated in the summer of 2023, following the collapse of a school roof that had previously been assessed as safe.

The government advised the immediate closure of public buildings containing RAAC until they could be assessed as safe or until remedial work had been completed. Identification of RAAC in all buildings that had not yet been inspected was commissioned in short order.

What action do building owners and managers need to take?

IStructE has put together clear guidance on the steps required to identify if a building is affected by RAAC and how to assess and manage any issues, as well as where to get support. Here is a brief summary:

  • Identification: Not all buildings constructed between 1950 and the mid-90s will have RAAC present, so determining this is the first action for building owners and managers. A guide is available for educational buildings, and experts such as Chartered Structural engineers, or surveyors, can assist in identification.
  • Assessment: If RAAC is present, the building must be evaluated by an appropriately experienced and qualified Structural or Civil Engineer, to assess for risks and identify if any immediate temporary remedial work is needed.
  • Solutions: A Chartered Engineer will propose necessary permanent remedial work and a timeline for completion, or re-inspection. These professionals follow a code of conduct and stay updated on RAAC.

You can find the full guidance here: IStructE – Managing structures with RAACs

Why is a Chartered or Incorporated Engineer required?

All work assessing and designing solutions to RAAC must be overseen by a Chartered/Incorporated Structural Engineer or Chartered Civil Engineer, who brings an additional depth of knowledge and expertise, ensuring that concerns related to RAAC are addressed at the highest level and with precision.

To become Chartered, Engineers are required to demonstrate professional experience over several years and must pass qualifying exams. In order to maintain their chartered status, they must engage in Continuing Professional Development (CPD). This ensures that they remain updated on the latest advancements in the field, technological innovations, and in regulations and best practices. All members of a qualifying organisation e.g., IStructE or the Institution of Civil Engineers (ICE), are committed to a code of conduct and must uphold the highest professional standards.

The benefit of early engagement

While the identification stage can be undertaken by a surveyor or experienced estate/maintenance manager if documentation is available, in many cases, it is not, and a structural or civil engineer would be required. Bringing in an appropriately qualified Engineer at the earliest stage can speed up this process and reduce risk.

Safety and risk management is paramount. Chartered Structural or Chartered Civil Engineers have the necessary experience to identify potential structural issues that might compromise a building’s integrity.

They will holistically analyse a building’s history, its construction methods, and its materials. Where RAAC is present, comprehensive assessments enable the identification of specific areas of concern, subsequently providing actionable and pragmatic recommendations. RAAC requires the deployment of both non-destructive and destructive testing in the evaluation process. These sophisticated methodologies, tailored to the particular requirements of the building, ensure the most accurate results.

An experienced structural or civil engineer is uniquely positioned to provide guidance on necessary remediation, from temporary supports to more comprehensive renovation strategies. Once potential problems are identified, a timeline of works is established and prioritised based on urgency to ensure the safety of both the building’s occupants and the general public. Their recommendations are underpinned by a commitment to professional codes of conduct, ensuring that all advice is not just technically sound but also ethically grounded.

How can WCS help?

WCS can provide a full package of services from identification to remediation, ensuring that structures affected by RAAC are safe and secure. Engaging with our team, led by Chartered Structural Engineers ensures that the client receives a holistic service, from the initial assessment to the execution of recommended actions.

If your organisation requires support with RAAC, contact WCS today for a consultation on how we can address your unique demands.