Chimneys and parapets
A fireplace is boarded and the pot at the top is open to the rain. What ventilation of that flue was lost at the room, and what rain path remains at the pot?
The ventilation lost at the room is the air that should have entered the flue through the fireplace, because the opening is boarded. The rain path that remains is the open pot: rain can still fall in at the top and run down a flue that no longer breathes into the room. Boarding stops the room vent. It does not cap the pot. The survey has recorded both. It has not seen a liner, and it has not tested whether the flue is dry behind the board. The lost ventilation is at the hearth. The weather path is still the open pot.
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?
An open fireplace lets the flue breathe from the room and gives any rain that gets in a way to be noticed. Boarding the opening closes that vent. If the pot is left open, rain still enters at the stack and can sit in a flue that no longer dries by a draught from the room. That combination is a closed bottom and an open top. The survey saw the board and the pot. It did not remove the board, and it did not camera the flue.
Ask a chimney specialist about ventilating the boarded flue and about capping the open pot, as two linked points. Tell the solicitor the room vent was lost at the board and the rain path at the pot remains. Do not pull the board off as a casual check. The survey has not said the breast is safe to open, and it has not seen the liner. How an unused flue should breathe is advice for that specialist, not a detail already drawn in the report.
What should you ask your surveyor?
- Is the fireplace boarded, so the room vent into the flue is lost?
- Does the open pot remain a rain path?
- Was the liner left unseen behind the board?
What are the typical next steps?
- Treat the board as lost ventilation at the room.
- Treat the open pot as a rain path the boarding did not close.
- Ask a chimney specialist before the board is removed.
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 board is neatly finished, is the flue sealed against rain?
No. A finish on the board is in the room. The pot is still open at the top, so the rain path remains. The ventilation lost is the opening that used to let the flue breathe into the room. A neat board does not cap a pot, and the survey did not see a liner behind it.
Should the pot be left open so the boarded flue can dry?
The survey has not recommended that. An open pot is the rain path that remains, and the room vent is already lost at the board. Leaving the pot open does not restore ventilation at the fireplace. It keeps the weather route. How a disused flue should be vented is for a chimney specialist. The report recorded the board and the open pot.