Chimneys and parapets
A disused flue has a vent in the breast and the pot was not capped in a way the surveyor could confirm. What moisture path remains if the flue is closed at the top only?
If the flue is closed at the top only, the moisture path that remains is inside the disused flue toward the vent in the breast. Rain may be kept out at the pot, but moist air can still sit in the stack, condense on the cold flue, and track to that vent or into the breast masonry. The surveyor could not confirm how the pot was capped, so even the closure at the top is unverified. The vent shows an opening at room level. The survey has not measured moisture in the flue and has not shown this path is active.
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 redundant flue that is sealed at the top and forgotten will often sweat. The air in it cools against the brick, condensation forms, and the water looks for a way out. A vent in the breast is put there so the flue can breathe into the room rather than wet the plaster in secret. If the top is closed and the vent is the remaining opening, that is the path. Because the cap itself was not confirmed, the report cannot even be sure rain is excluded.
A chimney contractor can confirm the terminal, fit a ventilated cap if that is what this flue needs, and check the breast vent is still open. Tell the solicitor the survey did not confirm the cap and did not measure damp in the stack. The note is not a specification for tanking the breast. Do not block the vent because the fireplace is unused. Closing the only room opening, while the top may already be shut, is how a damp flue is left with nowhere to breathe.
What should you ask your surveyor?
- Could you confirm the pot was capped, or was that unverified?
- Is the breast vent open, and which room is it in?
- Did you see salts or staining on the breast, or only the vent?
What are the typical next steps?
- Treat a top-only closure as leaving a moisture path to the breast vent.
- Ask a chimney contractor to confirm the cap and keep the flue ventilated.
- Do not block the breast vent on the assumption the flue is dry.
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 pot is open, does the breast vent still matter?
Yes, but it is a different arrangement. An open pot can let rain in, which the survey also could not confirm was capped. The vent is still the opening at the breast, and neither end was tested for moisture. No later decision about the vent was made, and this visit did not supply one.
Does a dry breast on the day mean the flue can be sealed at both ends?
No. A dry look does not measure the flue, and the survey has not said both ends can be sealed. Sealing a disused flue completely can trap the moisture this note is about. What happens next for the breastcap is outside this note and was not settled here.