Damp and moisture meters
The report mentions built-up condensation next to the underside of a cold flat roof. Has a drip the owner called a leak been tested, or only named?
Named, not tested. The drip the owner called a leak is recorded beside built-up condensation on the underside of a cold flat roof. BRE has described dripping of this kind as moisture that builds in the roof, rather than rain through the covering. A cold deck stays cold, so vapour from the rooms can gather and fall in drops. The survey has written down that pattern and the owner's word. It has not separated rainwater from condensation, and it has not decided which one is marking the ceiling.
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?
A cold flat roof places the insulation below the deck, so the deck stays cold. Moist air from the rooms can condense on that underside and drip, which is the built-up condensation BRE has described. From the room those drops look like a leak. The owner's label does not prove that rain has crossed the covering. The survey has named the mechanism beside the cold roof. It has not opened the covering and has not run a test that would split the two causes.
Tell the solicitor the report names built-up condensation and that a leak has not been proved. A roofing firm used to flat roofs can look at the vapour path and the covering as a later instruction, which this visit did not give. Do not let them price a full recovering from the owner's word alone. The survey has not chosen a repair. It has only kept condensation and an untested leak apart, and that split should stay with the papers.
What should you ask your surveyor?
- Did you see the drip, or only the owner's name for it?
- Is the flat roof cold because the deck sits above the insulation?
- Have both rainwater and condensation been left unproved?
What are the typical next steps?
- Treat the drip as named condensation, not as a proved leak.
- Pass the cold-roof note to a flat-roof firm without a chosen repair.
- Tell the solicitor the owner's leak label was not confirmed.
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 the ceiling is stained, must the covering come off?
No. A stain under a cold flat roof can be built-up condensation on the underside, the pattern BRE has described, or it can be rain. The survey has not opened the covering and has not tested which cause is active. The stain shows that moisture reached the ceiling. It does not by itself order the covering to be stripped.
Does naming condensation clear the roof?
No. Naming built-up condensation is not a clearance and not a proved leak. BRE has described dripping that comes from condensation rather than rain, and the report uses that reading without a test. Both the covering and the vapour path still need a look from someone instructed to separate them. The survey has not done that separation.