Chimneys and parapets
Should an unused flue be ventilated, and will a home survey check both ends?
An unused flue is often ventilated at the top and at the fireplace so moisture and soot deposits do not sit in a sealed shaft. A home survey can see a cap, a vent or a closed register if they are visible. It does not prove the flue is clear from top to bottom.
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?
Sealed breasts sweat. Salts and brown stains then get called “damp” and sometimes “rising damp”, even on an upper floor where rising damp is the wrong storey. Ventilation is a traditional way to let the stack breathe. It is not a guarantee against a failed flashing where the stack meets the roof.
The surveyor sees the room and the outside of the stack. They do not drop a camera down the flue as standard. Ask what was visible at the fireplace and at the pot. If you intend to fit a stove, that is a new installation under the building regulations for combustion appliances, not a note in the survey. Ask a competent installer. Costs vary with the flue lining.
What should you ask your surveyor?
- Was the fireplace open, vented, or boarded over?
- Could you see a cap or a ventilated cowl, or only the pot?
- Are you separating stack damp from a roof flashing leak?
What are the typical next steps?
- Do not board a fireplace shut because it looks tidier, until you understand how the stack was meant to breathe.
- Ask a sweep to comment before you reuse a flue. The survey is not a sweep.
- If salts are the only symptom, read the salts question before you buy a damp-proof course.
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 stuffed newspaper up the flue count as ventilation?
No. It is a blockage. Tell the surveyor if you find one, and do not light anything in that opening.
Will a Level 2 remove a gas fire to see the gather?
No. Lifting a fire is not a standard visual inspection, and gas work is for a Gas Safe registered engineer.