RAAC

Why should a woodwool slab roof not be reported to a lender as RAAC?

Because they are different decks. Woodwool is a slab of wood strands and cement, often used in mid-century flat roofs. RAAC is aerated concrete with reinforcement, which IStructE describes as precast roof panels. A surveyor who cannot tell should say the deck was not identified. Writing RAAC on a woodwool roof sends the lender and the engineer after the wrong material.

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?

Both can appear in the same era, which is why the confusion happens. The soffit of woodwool looks fibrous. RAAC is a bubbly concrete. Where the surveyor can see the difference, the report should use the right word. Where they cannot see the soffit, “deck not identified” is the accurate limit. IStructE’s RAAC route is for when RAAC planks are present or genuinely suspected.

Repairs differ. A woodwool deck that has got wet can crush and lose its hold on the covering. That is a flat-roof problem a competent roofer and, if needed, an engineer can describe. It is not the RAAC assessment. Ask the surveyor which material they mean before you fill in a lender form. There is no shared price for the two repairs.

What should you ask your surveyor?

Which material did you see, if you saw one?
If you did not see the deck, will you say so rather than name RAAC?
Is any recommendation about the covering, the deck, or both?

What are the typical next steps?

Correct the word before you send the report to a lender.
If the deck is unknown, say unknown. Do not pick the more frightening name.
If it is woodwool and it is wet, ask a roofing contractor who knows that deck what fails next.

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

Can a roof contain both?

An extension can have a different deck from the original. Ask the surveyor to separate them if they saw two roofs.

Is ordinary reinforced concrete RAAC?

No. Dense concrete slabs are a different material again. The aerated panel is the RAAC question.