7th March 2024

Misinformation about RAAC could do more harm than good


We ought not to assume that all buildings with RAAC aren’t safe, and articles that push this narrative are not helping, writes Billy Brand, senior structural engineer in our Leeds studio, in an article first published in New Civil Engineer, Building Design and EGI. Read Billy’s article here:


Reinforced Autoclaved Aerated Concrete (RAAC) is an aerated, lightweight concrete based material which does not contain aggregate unlike conventional concrete. It was generally used in construction between the 1950s and 1990s as a cost-effective, lightweight material with good thermal properties.

Whilst concerns regarding RAAC have been voiced since the 1990s, the collapse of a roof in a primary school in Kent in 2018 set alarm bells ringing which resulted in a more widespread awareness campaign about the material than during previous years.

Much of the focus since has been on school buildings with the Department for Education (DfE) being rightly particularly alert to the situation. RAAC has been discovered across many other public buildings, such as hospitals and council buildings, and even private dwellings.

Compromise to the structure of any building can be of serious concern regardless of its form of construction, and ascertaining building safety by engaging suitably qualified engineers and professionals should always be made a priority. Experts can then highlight the risks, and determine the safest course of action to be taken for building users and the wider community.

What concerns me is that the current reporting on RAAC — both in 2023 and continuing today — doesn’t necessarily tell the whole story, and acting on this somewhat sensationalist reporting could negatively affect people’s lives. Blanket statements that RAAC has a lifespan of ‘30 years’ as published by many media outlets are too simplistic.

The Institution of Structural Engineers’ statement in October 2023 confirmed this widely-shared claim is “misleading” and that “there is no specific data that we can point to that supports the stated 30-year lifespan”. The institution guidance provides a framework for qualified engineers to ascertain the risk associated with the presence of RAAC on a case-by-case basis through a series of different criteria, allowing for appropriate next steps to be taken.

This risk categorisation ranges from ‘low risk’ which suggests ongoing inspection and awareness campaigns for occupants is an appropriate course of action, through to ‘critical risk’ which prompts immediate action such as setting exclusion zones (or full evacuation depending upon the extent), temporary propping and eventually remedial works or full replacement. “If manufactured correctly, installed correctly, and appropriately maintained (for example no overloading and managing water ingress) throughout its in-use life then RAAC should perform comparably with similar materials”, it says.

The BBC News article also states that “The Health and Safety Executive said it [the material] was now beyond its lifespan and may ‘collapse with little or no notice’”.

This is cause for alarm, indeed.

In this specific case mentioned by the BBC, I trust that fellow professionals’ assessment which is leading to the potential removal of the tenants will have followed the correct procedures to ascertain what level of risk that RAAC in those particular buildings presented.

However, what these articles aren’t sharing is that the assessment of a building’s safety due to the presence of RAAC has to be taken on a building-by-building basis. What matters is the condition of the material, not its age, in conjunction with the strength of a regular maintenance and safety assessment and monitoring programme.

We’ve seen tenants with vulnerable children being asked to move out of their homes. It’s possible that the sick aren’t attending hospital appointments. And schooling has been disrupted for children who, following the pandemic need in-person interaction, socialising experience and structured education.

We ought not to assume that all buildings with RAAC aren’t safe, and articles that push this narrative are not helping. It’s the strength of the risk-monitoring strategy for the building in question and expert communications that are as important as any compromise to the material.

To spread that message effectively, we need our media sources to get on board.


Misinformation about RAAC could do more harm than good