Closing off a fireplace you do not use

Why it still needs attention

Water, animals and debris do not care whether you use the fireplace. A chimney with an open top lets rain in and can damp the walls inside the house. It also gives birds and other animals a place to nest. CSIA notes that unused flues can draw smoke from active fireplaces in an airtight house, and suggests a top-mounted damper on the unused one.

Common choices

Closing it in steps

• Decide the goal. Never use again, rarely, or maybe later.
• Have the chimney inspected so you know its condition, and so any problem is dealt with before it is closed.
• Cap the top. This is the single most useful step.
• Close the opening in a way that does not trap moisture and can be removed for inspection.
• Check for other users. If a furnace, boiler or water heater vents into the same chimney, do not close it off.
• Keep records of what you did, for you and for future owners.

What can go wrong

When you sell

Buyers and their inspectors will ask. A chimney inspection report, a cap you can point to and a note of how the opening was closed make it easier. If the fireplace is closed, say so, and tell buyers not to use it unless it has been inspected. See chimney inspection when buying or selling.

Check local rules

Altering a fireplace can be subject to local building rules, particularly if it is part of a permit. This guide is general information. Ask your local building department what applies before major changes.

Common misconceptions

"If I never use it, it does not need anything." Weather and animals do not wait for use.

"Bricking it up is safest." A permanently sealed chimney with a leaking top is a hidden water problem.

Sources

• CSIA, homeowner FAQs