Timber decay and woodworm
Wet rot is at the window sill only. Why has the survey not condemned the floor joist behind it?
The floor joist has not been condemned because the wet rot that was found is in the window sill, and the joist behind it was not seen. Wet rot is decay in timber that stays damp. Finding it in the sill identifies that piece. It does not, by itself, show that a separate joist under the floor is soft, reduced or even damp. The survey limits the finding to the timber it could reach. The joist remains unopened and undecided.
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?
Wet rot follows persistent moisture in the piece that is wet. A sill takes rain at the opening. A floor joist sits in a different place and may be dry, or it may be damp from another path the visit could not see. The surveyor does not condemn hidden timber from a rotten sill alone. Opening the floor, checking the joist end and reading the moisture there would be a further look. This visit did not do that opening.
Ask a carpenter or a timber specialist to lift enough of the floor to see the joist end nearest the wet sill, and to say whether decay has crossed from the window to the floor. Tell the solicitor the survey finding is the sill, not a proved joist failure. The lender should not be told the floor is condemned. The survey has not specified a repair to timber it did not expose.
What should you ask your surveyor?
- Was the joist end nearest this window visible at all?
- Is the moisture limited to the sill or also on the adjacent wall?
- What opening would be needed before the joist can be judged?
What are the typical next steps?
- Ask a carpenter to expose the joist end nearest the rotten sill.
- Tell the solicitor the finding is the sill, not a condemned floor.
- Do not describe the unseen joist as failed when you speak to the lender.
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 wet rot in a sill the same outbreak as dry rot?
No. Wet rot is decay that continues where timber stays damp, often in the wet piece itself. Dry rot is a different fungus with its own growth. The survey has named wet rot at the sill and has not sampled a fruiting body or identified dry rot. One rotten sill is not a cellar-wide dry rot finding.
Will painting the sill close the question of the joist?
No. Paint on the sill does not show what the joist end is doing behind the wall or under the floor. The joist was not opened, so decoration does not clear it and does not condemn it. Any paint is maintenance of the visible timber. The hidden end still needs a look if you want it decided.