The news cycle has brought RAAC (Reinforced Autoclaved Aerated Concrete) into sharp focus, causing concern for property owners and estate managers across the UK. Often dubbed “bubbly concrete,” RAAC was a popular lightweight construction material used extensively between the 1950s and 1990s. While once seen as an innovative solution for flat roofs and wall panels, its limited structural lifespan now presents significant challenges.
What exactly is RAAC?
RAAC is a lightweight, cellular concrete that lacks the traditional coarse aggregate found in standard concrete. This makes it lighter and easier to install but also significantly more porous. Over time, moisture can penetrate the concrete, leading to the corrosion of the internal steel reinforcement. Because the material is “aerated,” this corrosion is often hidden from view until a structural failure occurs.
Why is it a problem now?
The primary issue with RAAC is its design life. Most RAAC planks were intended to last around 30 years. As many of these buildings are now reaching 40, 50, or even 60 years of age, the material is exceeding its safe performance window. Common signs of failure include:
- Excessive Deflection: Visible sagging in roof planks.
- Cracking: Particularly near the “bearing” (where the plank sits on a wall or beam).
- Water Leaks: Which accelerate the internal rusting of reinforcement bars.
The Importance of a Specialist Survey
A standard building survey may not always identify RAAC, as it is often hidden behind suspended ceilings or roof finishes. A Specialist RAAC Audit is required to:
- Confirm Presence: Identify if the material is indeed RAAC or a similar-looking lightweight concrete.
- Assess Condition: Measure the degree of deflection and check for reinforcement “spalling.”
- Risk Categorisation: Rank the urgency of remedial works from “Monitor” to “Critical.”
How MM Building Surveyors Can Help
With over 25 years of experience in technical audits, our team provides a hands-on approach to RAAC identification. We utilise non-destructive testing and, where necessary, drone technology to inspect high-level roof decks safely and efficiently. Our reports are clear, succinct, and designed to give property owners a definitive roadmap for safety and compliance.
Do you suspect your building contains RAAC? If your property was constructed or extended between 1950 and 1995, an inspection is highly recommended.