RAAC in Listed Buildings Guide
NEW GUIDANCE on Reinforced Autoclaved Aerated Concrete (RAAC) in Listed Buildings has been launched by Purcell.
The document, which has been endorsed by the Twentieth Century Society, Society for the Protection of Ancient Buildings (SPAB), and the Institute of Historic Building Conservation (IHBC), has been led by Max Thomson, Building Surveyor at Purcell in collaboration with Chris Waterman, Parliamentary Policy Advisor and Building Safety Specialist.
Purcell, architectural practice and heritage consultants, funded the research and publication of the guide as part of its R&D programme. The company hopes it will share what Purcell considers to be the best currently available guidance for anyone who is responsible for a listed building that may be affected by the presence of RAAC.
The potential presence of RAAC is by no means limited to 20th century buildings, but buildings of any period that may have undergone alterations or interventions from the 1950s to 2000.
RAAC in Listed Buildings
The publication sets out professional guidance for building owners, heritage stakeholders, asset and estate managers, and local and central government.
Max Thomson, building surveyor at Purcell, said: “The motivation driving this project has been to provide professional guidance that will help building owners and custodians find good to solutions to reduce risk to people and their listed buildings.
“Long-term solutions for the replacement of RAAC in listed buildings need to be developed with care and specialist expertise and we hope this guidance forms the basis for procuring the necessary solutions for risk mitigation and conserving the historic built environment. This is not just about protecting our most treasured buildings; it is a matter of public safety”.
About RAAC
Reinforced autoclaved aerated concrete (RAAC) is a lightweight, aerated, or “bubbly” material that was used mostly in flat roofing, but also in floors and walls, between 1950 and 2000. It is a cheaper alternative to standard concrete, is quicker to produce and easier to install but less durable than standard concrete.
RAAC panels are susceptible to structural failure when exposed to moisture. The aerated texture can allow water to enter the material. If that happens, steel reinforcing bars within the panels can decay, rust and weaken.
When RAAC is removed, the weight and thermal efficiency difference of the replacement product must be considered. Additionally, its structural behaviour differs significantly from traditional reinforced concrete.
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