New and recently installed concrete flooring not affected by RAAC crisis

The Department of Education (DfE) has ordered over 100 schools to close due to the risk of reinforced autoclaved aerated concrete (RAAC) failing and causing ceilings to collapse, leading some building owners to question the safety of concrete.

Technically, RAAC is not concrete, but a weaker material with similar properties. It can deteriorate if exposed to water from leaking pipes or damaged roofs. RAAC is made from materials that are aerated to form lightweight blocks. It was mainly used on flat roofs, but has a lifespan limited to around 30 years. It was used because it was cheaper and easier to make than standard concrete.

RAAC was rarely used after 1980, and in 2018, a school roof collapsed, fortunately, during the weekend. This caused the Department of Education and the Local Government Association to issue warnings to schools about the unreliability of RAAC.

RAAC was used in schools and colleges built or modified from the 1950s to the mid-1990s. Therefore, any later-constructed buildings have nothing to worry about.

Flooring contractors who have recently installed new concrete flooring, and those who plan to do so, will use full-strength concrete. Some RAAC is still manufactured, but research has found it to be safe compared to RAAC panels made between the 1950s and 1970s, provided it is correctly manufactured and installed.

Building owners can have their older buildings constructed between the 1950s and 1990s inspected to determine if RAAC was used.