Discovering Reinforced Autoclaved Aerated Concrete (RAAC) in Buildings
In recent news, Reinforced Autoclaved Aerated Concrete (RAAC) has garnered attention. But what exactly is RAAC, and what crucial details should you be aware of?
Reinforced Autoclaved Aerated Concrete (RAAC) is a lightweight steel reinforced concrete commonly used for structural units such as wall panels, floor and roof planks.
First created in the 1930s, RAAC products were introduced into the UK in the 1950s and used up until the mid-1980s. They were popular for use as roof decking as they provided good thermal performance and were lightweight and fire resisting.
When was RAAC used?
RAAC was predominantly used in commercial buildings and they were popular in public sector buildings including both education and healthcare. The problems with RAAC are fundamental and include inherent design, workmanship, and durability issues. Early signs of problems are typically excessive deflection and cracking but catastrophic failure can occur with little or no warning.
This is not a new problem as by the 1980’s some of the early RAAC planks had failed. The Building Research Establishment (BRE) published a paper in 1996 related to RAAC and in 2002 the BRE recommended monitoring and a lifespan of 30 years.
A school roof failure in Essex in 2018 led to schools and education estates being advised to identify and assess RAAC. An alert by the Standing Committee of Structural Safety followed in 2019 and NHS England identified several hospitals with RAAC at that time.
Department of Education estates guidance related to RAAC was most recently updated in late August. This follows sudden collapses where RAAC panels appeared to be in good condition. A reassessment of risks has recently resulted in the decision to close a number of schools.
NHS Property Services (NHSPS) has reported a total of seven cases of RAAC relating to their properties with works completed at four and one health centre closed.
Which buildings have it?
RAAC could be present in any building that was built, extended, or altered between the 1950s and 1990s. The majority is likely to have been used in the public sector but it was used elsewhere and could present a significant safety and financial risk to building occupiers and owners.
Primary care property owners and occupiers need to consider commissioning an experienced Chartered Building Surveyor or Structural engineer to provide further advice.
Further Information
Author: John Clark BSc (Hons) MRICS. John is a Chartered Building Surveyor with experience in identifying and providing advice on RAAC. For further info please contact John via email at john.clark@argroup.co.uk
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