RAAC

What is RAAC, in the words a buyer needs when a survey mentions it?

RAAC is reinforced autoclaved aerated concrete. The Institution of Structural Engineers says it has been used in the UK since the late 1950s, most commonly as precast roof panels in flat roofs, and that structural deficiencies became apparent in the 1990s. A home survey is not the investigation IStructE describes. If the surveyor suspects RAAC, the condition of those panels has to be assessed by a chartered or incorporated structural engineer.

Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.

What is the fuller explanation?

IStructE’s public statement is aimed at people responsible for buildings of that period who are unsure of the construction: identify, then assess, then decide on solutions. The assessment guidance is for structural engineers using their own judgement, not for a buyer with a photograph. Ordinary cavity-brick houses with timber roofs are not the buildings this material is known for. Flat-roofed blocks and some public and commercial buildings of the period are the usual context.

Do not hear “RAAC” and decide every concrete soffit is dangerous, and do not ignore the word if the surveyor has used it. Ask what they saw: panel width, a bubbly texture, deflection, cracking or staining, or only a guess from the age. Then follow IStructE’s route to an engineer if the panels may be RAAC. There is no IStructE price for replacement. The engineer’s assessment comes before a builder’s quote.

What should you ask your surveyor?

What did you see that made you say RAAC rather than another concrete or a timber roof?
Which roofs or floors, and could you see the soffit?
Are you recommending a structural engineer?

What are the typical next steps?

Do not drill the soffit to “check the bubbles”.
If RAAC is suspected, instruct a chartered or incorporated structural engineer, as IStructE advises. Do not ask a roofer to sign it off.
Tell your lender the exact sentence. Do not translate it into “roof condemned” unless the engineer has said so.

Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.

Also asked about this

Is RAAC the same as asbestos cement?

No. One is a reinforced concrete panel. The other is a fibre-cement sheet. They are different materials and different trades.

Does a Level 2 always identify RAAC?

No. It is a visual inspection. A hidden soffit is a limit. Suspicion is not a completed IStructE assessment.