Timber decay and woodworm
A converted chapel has deathwatch-type holes in one oak truss and the new softwood joists beside it are clean. Why should the new joists not be sprayed because of that truss?
The new joists should not be sprayed because of that truss. The deathwatch-type holes are in one oak truss, and the new softwood joists beside it are clean. Spraying the joists would treat timber that showed no attack, on the back of a different piece of oak. The survey has recorded holes of that type in the truss and a clean face on the new joists. It has not found flight holes in the softwood, not confirmed live insects, and not prescribed a spray. The truss does not convict the joists.
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?
Deathwatch is associated with hardwood, and old oak in a chapel roof is where those holes are often seen. New softwood joists are a later structure. A clean surface means the inspection did not see the same damage there. Treatment, if anyone proposes it, has to follow the timber that needs it. Blanket-spraying sound new joists because an oak truss has old-type holes spends effort on the wrong wood and can be read as if the survey had ordered it. The survey ordered nothing of the kind.
Ask a timber specialist to look at the oak truss on its own, and to say whether the holes are historic or active. Point out that the new joists were clean. Tell the solicitor the survey has not recommended spraying those joists. Do not accept a quote that treats the whole floor because of one truss. The evidence was split: holes in the oak, none recorded in the new softwood.
What should you ask your surveyor?
- Were the deathwatch-type holes confined to the oak truss?
- Were the new softwood joists recorded as clean?
- Have you avoided recommending a spray of those joists?
What are the typical next steps?
- Do not spray the new joists because of the oak truss.
- Ask a specialist about the truss itself.
- Reject a whole-floor treatment that the survey did not ask for.
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
If one new joist later shows a hole, does the earlier note collapse?
A later hole would be a new finding on that joist. It would not rewrite the day the joists were clean, and it still would not justify spraying timber that remains clean. The survey's point stands for what it saw: holes in the oak, and no reason from that truss to spray the new softwood.
Are old holes in oak proof the insects are active now?
No. Deathwatch-type holes record that something made them, not that insects are active this week. The survey did not confirm live infestation. That uncertainty is about the truss. It is a further reason not to spray clean new joists on the truss's account.