RAAC

Why do surveyors talk about RAAC on flat roofs more than on a pitched tile roof?

Because IStructE says RAAC was most commonly used as precast roof panels in flat roof construction. A traditional pitched roof with timber rafters and tiles is a different structure. A flat roof with concrete planks from the late 1950s onward is where the question arises. The survey still has to see the plank, not infer it from the word “flat”.

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?

Flat roofs are already a place surveys struggle: coverings hide the deck. RAAC is about the deck, not the felt on top. A surveyor may see the soffit from inside a cupboard or a stair and still not see the bearings where the panels sit on the wall. IStructE’s assessment guidance exists because the way the panels bear and the way they have deflected are engineering judgements.

If your flat roof is timber, ask the surveyor to say so and retire the RAAC question. If they can see concrete planks and are unsure, do not reroof the felt and ignore the deck. The covering and the panels are different. An engineer looks at the panels. A roofer looks at the waterproofing. Neither price is in the IStructE statement.

What should you ask your surveyor?

Is the deck timber, concrete planks, or unseen?
Could you see the panel ends where they bear on the wall?
Is the felt failure a separate comment from the deck?

What are the typical next steps?

Read the deck and the covering as two lines in any quote.
If the deck may be RAAC, stop and get the engineer. Do not overlay the felt first.
If the deck is timber, deal with the flat-roof covering on its own evidence.

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

Are all flat roofs from the 1960s RAAC?

No. Timber, woodwool and ordinary concrete were also used. Age is why someone looks. It is not an identification.

Does a pitched roof with a small flat dormer count?

Only the flat part could be a plank. The tiled slope is not RAAC because the dormer is flat. Ask what the dormer deck is.