Damp and moisture meters

Does a tanked basement mean the surveyor has signed off the waterproofing?

No. Tanking is a lining or barrier someone has applied. A home survey can see stains, salts or a musty smell on the day. It cannot test the tanking, the land drain or the water pressure behind it. Approved Document C is about moisture resistance in building work, not a pass certificate for an old cellar.

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?

Below-ground rooms get damp from the ground as well as from leaks and from humid air. A painted waterproof coating, a membrane or a drained cavity are different systems, and each fails in a different place: at a joint, at a pump, or where a later hole was cut for a pipe. The surveyor usually cannot see the hidden face. The honest note says what was visible and what was not opened.

Government guidance on damp and mould still starts with cause and health, and it is written for rented housing providers, not as a buyer’s price list. The Property Care Association expects the mechanism to be identified before a treatment is sold. Ask for any guarantee, the pump service record and what happens if the pump stops. A missing paper is not proof the system has failed. It is a gap your solicitor and a damp specialist can actually ask about.

What should you ask your surveyor?

Could you see the tanking, a drained membrane, or only decorated walls?
Is there a pump, and was any service record offered?
What would need opening up before you would rely on this room?

What are the typical next steps?

Do not line the room again before anyone has found where water enters.
Ask the seller for guarantees and pump invoices. Absence of paper is a question, not a defect rating by itself.
If you need the cellar as living space, instruct a specialist who will describe the system, not only quote to coat it.

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 a basement the same as a cellar in a survey?

Surveyors often use the words for a room below ground. The legal use of the room is a question for the plans and your solicitor, not for the moisture meter.

Does Approved Document C apply unchanged to a Victorian cellar?

It is the building-regulations document for moisture resistance in work that needs approval. It is not a retrospective test the surveyor applies to old walls.