RAAC stands for Reinforced Autoclaved Aerated Concrete. It was primarily used in construction from the mid-1950s to the mid-1990s, to create prefabricated roof, floor and wall panels.
It differs from normal concrete because it is made without aggregate and has air voids, giving it a ‘bubbly’ texture. The material is lighter than traditional concrete, meaning the panels could be transported to site and lifted into place much more easily and quickly, shortening construction time.
The downside of the material is that the voids allow water to easily enter the panels, causing reinforcement bars to rust and spalling of concrete, causing weakness to the structure.
As flat roofs are most susceptible to water ingress, the majority of structural issues have been related to RAAC roof panels. Buildings constructed with RAAC therefore require regular proactive maintenance, with in-depth monitoring of the panels and their condition. Without it, serious structural problems can occur and in some cases, catastrophic collapse, which sadly occurred at a school in Kent in 2018.
How to recognise if your building has RAAC
As highlighted above, construction with RAAC was prolific from the mid-1950s to the mid-1990s. If your building dates between this time, it’s worth getting it checked by a structural engineer to determine if the material was used, especially as it has been determined that RAAC planks have an estimated life span of 30 years.
Other telltale signs are if your building has a flat roof as this was the most common approach to using the material at the time, and if the roof/floor feels solid, unlike timber which can feel bouncy or sound hollow. However, we would recommend advice is taken from a qualified structural engineer or surveyor to determine if RAAC is present in your building.
Determining the amount of damage and risk
If RAAC has been found in your building, a structural engineer can determine any damage and risk by looking for concrete cracking, spalling, and the amount of panel that is supported off the structure. Get in touch with an experienced professional as soon as possible if you notice signs of cracking or spalling to concrete.
The fact that the material holds water can make damage difficult to notice by eye. In some cases, internal reinforcement has been rusting without concrete spalling which adds to the complexity of the assessment. Measurements should therefore be taken of how much the panels are deflecting.
How much does a RAAC survey cost?
Our experienced structural engineers at AWA will be able to determine whether RAAC is present in your building.
A thorough survey will be carried out and a report provided to state if there is RAAC in the building. If it is present, the next steps will be set out in the report. We are here to support you if subsequent work is required.
Survey fees are dependent on the size and complexity of the building, as well as the distance to travel from our offices in Romsey and Bath. Get in touch on 01794 524447 for a quote.