Timber decay and woodworm
If roof timbers are stained under a leak, is that automatically rot?
No. A stain means they have been wet. Rot means the wood has decayed. A surveyor can see staining and can probe softness where they can reach. A stained but firm rafter is a leak to fix. A soft rafter is decay and may need a carpenter. The Property Care Association’s point is that the moisture has to stop, or any repair is temporary.
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?
Lofts under a slipped tile or a failed valley show tide marks on rafters and on the felt. The timber may still be sound. Probing every rafter is not a Level 2. The report should say what was reached. If the surveyor says “possible decay” they are not sure. Ask them what was soft.
Do not sister every rafter because of staining. Fix the covering first, then replace what is actually decayed. A roofer and a carpenter may both be needed. Neither price is in the RICS guide. Get them to see the loft. Spraying stained timber does not mend a hole in the roof.
What should you ask your surveyor?
- Which timbers were soft, and which were only stained?
- Where is the leak relative to those timbers?
- Did insulation stop you seeing the ceiling joists?
What are the typical next steps?
- Make the roof watertight before you decorate the ceiling.
- Ask for a quote that separates covering repairs from timber repairs.
- Do not bury wet timbers in new insulation and hope.
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 staining mean dry rot?
No. Dry rot has its own signs. A brown stain under a leak is usually a leak. Ask if strands or a fruiting body were seen.
Will the stain go away when the leak is fixed?
The water stops. The mark may remain. A mark is not a structural section size.