Basements and cellars
Why are timbers built into a damp cellar a different comment from a stain on the wall?
Because timber in persistent moisture is where wet rot, and sometimes dry rot, starts. A stain on masonry may be only masonry. A sole plate or a joist end in that stain can be soft. The Property Care Association treats fungal decay as a moisture problem as well as a timber problem. The surveyor often cannot see the end of the joist without opening up.
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?
If the report says the cellar timbers were not inspected, do not read the floor above as proved. Deflection, a musty smell and fruiting bodies are clues. None of them is a laboratory identification. Do not spray the joists because the wall looks damp.
Opening up is a separate instruction. Costs vary with how much is covered. No price is stated here. Deal with the water path, or the next timber will rot too. A damp-proofing quote that ignores the joist ends has not read the finding.
What should you ask your surveyor?
- Which timbers could you see, and were any soft?
- Is the moisture active, or only historic staining?
- Would you need opening up before anyone specifies a spray?
What are the typical next steps?
- Do not box the timbers in before they are seen.
- Ask a timber specialist to separate decay from harmless staining, and to say what must be opened.
- Fix the water. Do not pay for a chemical treatment of dry, historic wood.
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 every mushroom in a cellar dry rot?
No. Fruiting bodies differ. The survey should not name a species it is not sure of. A specialist identifies it.
Does a new concrete floor prove the joists above are dry?
No. Concrete can hide a wet sole plate at the edge. Ask if that junction was visible.