Timber decay and woodworm
What should you ask if plywood roof sheathing has insect holes but the rafters do not?
Ask which board and whether the rafters were checked. Some beetles attack the starch in certain plywoods and hardwoods and do not move into the structural softwood. A surveyor who writes “woodworm in the loft” without saying plywood or rafter has not given you a specification. Treatment of the wrong timber does not answer the question.
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?
The Property Care Association’s advice starts with identifying what is active and what is damaged. Flight holes in a plywood sarking board can look alarming and still leave the rafters sound. The reverse is also true. The survey should separate them. If the plywood is the deck of a flat roof, the covering above it may also be the leak that wetted it.
Do not spray the rafters because the board has holes, and do not replace the rafters because the board has holes. Ask a timber specialist to say if the attack is active and if the board is still doing its job. There is no standard price. A flat-roof deck and a pitched-roof rafter are different repairs.
What should you ask your surveyor?
- Was it the plywood, the rafters, or both?
- Was there fresh dust on the board?
- Is the board part of a flat roof that is also leaking?
What are the typical next steps?
- Get the sentence clarified before you pay for treatment.
- If only the plywood is affected, ask whether it needs replacing or only monitoring.
- If there is a leak above it, fix the covering in the same plan. Spray will not dry a wet deck.
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 plywood “structural”?
When it is a deck or a sarking that the roof relies on, yes. A packing piece is not. Ask what the board is doing.
Does furniture beetle prefer plywood?
The common furniture beetle is usually in softwood. Other beetles prefer certain hardwoods and plywoods. The survey is not a laboratory. Location and whether the dust is fresh matter more.