Damp and moisture meters
Damp staining is inside a service cupboard around pipes, and the outside wall is dry. Why should that not be reported as penetrating damp from rain?
That staining should not be reported as penetrating damp from rain, because it is inside a service cupboard around pipes and the outside wall is dry. Rain penetrating the external wall would be expected to relate to the outside face. Here that face was dry, and the marks sit on the services. The survey records staining around pipes. It has not tested the pipework, and it has not proved a leak. Naming rain through the wall would pick the wrong path when the wet marks are in the riser.
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?
Service cupboards hold soil pipes, wastes and often heating pipework. Condensation on a cold pipe, a weeping joint or a leak from the flat above can mark the inside of that cupboard while the external wall stays dry. Penetrating damp from rain tracks from the weather face inward, and you would expect some relationship with that face. A dry outside wall breaks that relationship. The honest location is the pipes. The survey has not pressure-tested them. It has located the stain.
A plumber, not a damp-proofing contractor aimed at the external wall, is the trade that matches pipes in a cupboard. Ask the managing agent if the riser serves other flats, because the stain may not be yours to open. Tell the solicitor the survey is not calling this rain penetration, so a seller comment about the outside wall can be set aside. The untested part is the pipework. The rejected label is penetrating damp from rain.
What should you ask your surveyor?
- Was the staining around the pipes rather than on the outside wall?
- Was the external face dry where you could see it?
- Did you test the pipes, or only record the marks?
What are the typical next steps?
- Report the marks as associated with the service pipes.
- Do not call them penetrating damp from rain.
- Ask a plumber, and the agent if the riser is shared, to trace the stain.
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 a pipe is sweating, is that still not rain?
Sweating is condensation on a cold pipe, which is a services mechanism inside the cupboard. It is not rain driven through the external wall. The survey may not have proved a leak, but sweating still points at the pipe. The dry outside wall remains the reason not to call it penetrating damp.
Does dry plaster just outside the cupboard keep the problem in the riser?
It supports that reading. If the cupboard lining is marked and the wall beyond it is dry, the wetting is local to the pipes. The survey has not mapped every void. It has enough to refuse a rain-penetration label for this stain.