Roofs and flat roofs
BRE has described dripping that is built-up condensation rather than a leak. Why has this survey not decided which one this drip is?
This survey has not decided which one this drip is. BRE has described dripping that can be built-up condensation rather than a leak, and a single drip does not separate the two. The visit recorded water or staining where it was seen. It did not run a test that splits condensation inside the build-up from a failed covering, and it has not claimed which mechanism is wetting this ceiling. Both can leave a drip. The cause stays open.
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?
Built-up condensation forms when moist air meets a cold layer inside a flat roof and water later appears indoors. A leak is rain passing through a failed membrane or a poor junction. The mark on the ceiling can look the same. Nothing in this inspection opened the roof, traced a path through the deck, or logged conditions that would favour one cause. Inventing a test, or picking a winner from the stain alone, would go beyond what was seen.
Tell the solicitor the drip is recorded and the cause is not decided, so any enquiry of the seller should ask about roof coverings, ventilation and previous repairs without assuming a leak. A roofing specialist can investigate the build-up if you instruct that later. The survey has not appointed one and has not decided the covering has failed. Do not tell a lender this is proved condensation, or a proved leak, on the strength of the drip.
What should you ask your surveyor?
- Was the drip recorded without a cause being chosen?
- Did the visit open the flat-roof build-up?
- Are previous roof repairs described anywhere outside this report?
What are the typical next steps?
- Leave the drip as either condensation or a leak, undecided.
- Ask the solicitor to enquire without assuming a failed membrane.
- Instruct a roofing specialist if the build-up is to be investigated.
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 a dry day of the visit prove the covering is sound?
No. A dry day only describes the weather at the inspection. Condensation and rain leaks can both be absent at that moment and still be the cause at other times. The survey did not claim the roof is watertight. It recorded a drip and left the mechanism open, which a single dry visit cannot close.
Should the seller's explanation be written into the report as fact?
Only as what the seller said, if it was said, and not as the survey's finding. A seller may believe the drip is condensation or a leak. The visit did not test either account. Keep that comment separate, and do not let it decide which mechanism BRE described is the one at work here.