Damp and moisture meters
The report mentions waney-edge boards next to a blocked vent gap. Has staining on the sheathing been tested, or only named?
Staining on the sheathing has only been named, not tested. Waney-edge boards are the outer cladding, with the natural edge of the board left on. A vent gap behind that cladding is there so the cavity can breathe, and the report says that gap is blocked. The sheathing is the layer behind the cavity. The survey did not open the boards, did not sample the stain, and has not decided the sheathing is wet or decayed.
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?
Waney-edge boards are a rainscreen, and a gap lets air move behind them. Block that gap and the cavity loses the path that was detailed. Sheathing is the layer that closes the frame behind the cavity. The stain was named from a limited sight, not from a moisture reading. It can be old tannin, dirt or water, and this paragraph does not choose among those.
Tell the solicitor the blocked gap and the sheathing stain were not turned into a test. If the cavity must be seen, a cladding contractor can open an agreed board, which the home survey did not do. The lender has no moisture result for the sheathing. Do not assume the stain means the frame has failed. Ventilation of the gap and the condition of the sheathing both stay open until someone looks properly behind the waney-edge boards.
What should you ask your surveyor?
- Was staining on the sheathing only named?
- Did you see the blocked vent gap without opening the boards?
- Have you left the cause of any stain undecided?
What are the typical next steps?
- Treat the sheathing stain as named, not tested.
- Ask a cladding contractor if a board must be opened.
- Tell the solicitor the cavity behind the waney edge was not proved wet.
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
Does a blocked gap by itself rot the sheathing?
Not as a finding. A blocked vent gap removes an air path. It does not measure water in the sheathing. The survey named the blockage and named staining. It did not test either. Rot would be a further conclusion, and this visit did not reach it.
If the waney edge looks weathered, is that the stain on the sheathing?
No. Weathering on the outer board is the face you can see. Sheathing is behind the cavity. The two can both be mentioned and still be different surfaces. The survey did not treat outer greying as a test of the inner board. The stain that was named stays untested.