Reinforced Autoclaved Aerated Concrete (RAAC), commonly known as RAAC, has long been utilised as a cost-effective construction material in flat roofing, floors, and walls, particularly during the period spanning from the 1950s to the 1990s.

Initially praised for its lightweight properties, ease of production, and quick installation, recent findings have cast a shadow over its structural integrity and safety.

Keep reading as we explain the impact of deteriorating RAAC in the construction industry.

RAAC’s shortcomings become evident

RAAC, an aerated and lightweight material, boasts a shorter lifespan of approximately 30 years compared to traditional concrete. Its structural behaviour significantly differs from traditional reinforced concrete, rendering it vulnerable to moisture-induced structural failure.

Moisture can infiltrate RAAC through its aerated composition, leading to rusting and decay of any reinforcing materials. While some attempts have been made to mitigate these concerns, such as coating RAAC brackets with materials like bitumen and roofing panels, it is crucial to understand that RAAC fundamentally differs from traditional concrete and is inherently weaker due to its manufacturing process.

Alarming signs of deterioration

Disturbingly, Loughborough University has reported that tens of thousands of structural panels made from RAAC are already in use, and many of them exhibit signs of wear and deterioration.

The Health and Safety Executive (HSE) has warned that RAAC panels are now beyond their intended lifespan and may pose a significant risk of sudden failure, especially in aging structures. Recent incidents, including the abrupt closure of schools due to structural beam failures, have brought these safety risks into sharp focus.

Impacted structures and buildings

The impact of these issues is primarily felt by buildings constructed between the 1950s and 1990s, including schools and hospitals. Identifying and assessing the condition of RAAC elements has become imperative to ensure building safety and longevity.

Residential buildings, both purpose-built during this period and converted structures, may also be at risk. This concern primarily encompasses local authority-built properties within a specific 40-year timeframe.

Historical awareness and concerns

A 2002 HSE report emphasised that RAAC panels over 20 years old are likely to have compromised integrity and may collapse without warning. In some cases, panels may not have met regulations during installation. Concerns about the structural differences and risks associated with RAAC have persisted since the 1960s, raising questions about its suitability when compared to traditional concrete.

Short-term exposure to moisture can reduce RAAC’s strength by approximately 13%, while prolonged exposure to polluted air can lead to a staggering 40% reduction. Worries about aging RAAC panels first emerged in the 1980s and 1990s when building collapses necessitated demolitions. The government’s awareness of the issue dates back to 1994 when it initiated monitoring of public sector buildings containing RAAC. New guidance has been issued in 2021 and 2022 regarding the management of RAAC, and a questionnaire was sent to responsible bodies in 2022 regarding its use in schools.

Prioritising safety in building construction

While expert advice suggests that RAAC is not in a critical condition, recent events have unequivocally demonstrated that it can pose a danger. Some schools previously considered low risk have experienced collapses, resulting in closures. The safety of buildings containing RAAC remains a top priority for the construction industry.

Cardinus data and services can help

We have already run the basic data from our INDIGO software system to discover how many buildings may be in scope and possibly contain RAAC.

There’s currently no requirement to carry out structural surveys on all buildings; however, it would be prudent to take a risk-based approach to identify buildings where there may be an issue.

At this time, it is not thought that there is widespread use of RAAC in private schemes. We will continue to monitor the situation for any changes and advise our clients accordingly.

If you’re concerned that your building may be affected by deteriorating RAAC or have any questions about the risks of RAAC, please email [email protected] or call 020 7469 0262.