Caring for a Fireplace You Never Use

Why an idle chimney still wears out

Most chimney deterioration comes from outside, not from fires. Rain soaks into a cracked crown or porous brick, freezes and expands in winter, and slowly breaks the masonry apart. Flashing ages along with the roof. None of that stops because the fireplace is cold.

CSIA's homeowner FAQ notes that the annual inspection called for in NFPA 211 applies to all chimneys, used or not, because animals can nest in them and other deterioration can make them unsafe to use.

There is also a second reason: the chimney may share a structure with flues that are in use. A furnace or water heater flue running beside an idle fireplace flue depends on the same crown, the same masonry and sometimes the same cap.

Water: the main threat

An uncapped, unused flue is an open pipe into the house. Rain falls straight down it onto the damper and firebox. Over time that can mean:

• A rusted, seized or rotted-through throat damper.
• Water stains, white mineral deposits or crumbling mortar in the firebox.
• Damp, musty smells, especially in summer.
• Water damage to walls, ceilings or floors near the chimney.

Water also enters through the crown, flashing and brick. A cap only addresses the flue opening. See Why is my chimney leaking? for the other paths.

Animals and debris

A quiet, unused flue is attractive shelter for birds, squirrels and raccoons. Nests and debris can block the flue completely. That matters for more than the fireplace. CPSC warns that birds, animals and insects nesting in vents can block exhaust and force combustion gases into the home, which is a concern if any other appliance shares or connects to that chimney.

Do not try to smoke out or trap animals in a chimney yourself. Some species may be protected, and young animals may be present. See Animals and nests in the chimney and chimney animal removal.

Drafts, odors and air pressure

An open flue lets warm air escape in winter and outside air, smells and humidity come in. Old soot and creosote in the flue can smell strongly in humid weather even if the fireplace has not been used for years. See Why does my fireplace smell?

When exhaust fans and dryers run in a tight house, air can be pulled down an unused chimney. CSIA notes that this can bring exhaust from other appliances down an unused flue, and lists makeup air and top-mounted dampers as ways to address it. Keeping the damper closed helps, but working CO alarms are still essential.

The top of the chimney matters most

For an idle chimney, the parts that face the sky do most of the protecting. Brick Industry Association guidance on residential chimneys describes a top that overhangs the brick, a flexible seal where the crown meets the flue liner, and base flashing and counterflashing that overlap where the chimney passes through the roof. When any of those fail, water gets into the masonry whether or not the fireplace is used.

Problems at the top are also the hardest for an owner to notice, because the only symptom may be slow staining or damage inside a wall months later. That is why the periodic inspection of an unused chimney focuses on the crown, cap, flashing and upper masonry as much as on the flue.

A cap is a small part with a large effect here. A trade article from the Mason Contractors Association of America lists keeping out rain and snow and keeping out animals among the main jobs of a chimney cap. See Crown vs. cap.

Ways to protect an unused fireplace

Never seal a flue that is connected to, or shares an opening with, any working appliance. Anything that blocks the fireplace flue must be clearly tagged and removed before a fire is ever lit. For details on the first two options, see chimney caps and chimney dampers.

A simple routine for an idle fireplace

1. Twice a year, look at the chimney from the ground for a missing cap, loose brick or damaged flashing.
2. After heavy storms, check the firebox and nearby walls and ceilings for water.
3. Every few months, open and close the damper so it does not seize, then leave it closed.
4. Listen and smell. Scratching, chirping or new odors mean something has changed.
5. Keep CO alarms working on every level and near sleeping areas.
6. Have the chimney inspected on the annual schedule, or at least before any change in use.

Before you use it again

If you plan to use a long-idle fireplace again, or you just bought a house where nobody knows when it was last used, have it inspected before the first fire. Typical findings in a long-unused chimney include nests and debris, a rusted damper, deteriorated mortar or crown, old creosote, and liner damage that no one noticed.

On our visits, the assessment includes a camera look up the flue when it allows, and you get findings with photos before any repair is scheduled. See chimney inspection. If you are buying a home, see Buying a home with a fireplace.

If you never plan to use it

Some owners decide to retire a fireplace for good. Options range from capping and closing it off properly, to converting it to gas, to removing all or part of the chimney. Each has trade-offs for water, structure, other flues in the same chimney and permits. See Should you remove an unused chimney? and Converting a wood fireplace to gas.

Questions homeowners ask

Sources

1. CSIA: Homeowner FAQs
2. U.S. CPSC: Seasonal heating system inspections to prevent CO deaths
3. Fine Homebuilding: Installing a flue-top damper (PDF)
4. Masonry Magazine (MCAA): Installing the correct chimney cap
5. Brick Industry Association, Technical Note 19B: Residential Chimneys, Design and Construction (archived PDF copy)

This guide is general information. It can't diagnose a specific chimney; an inspection can.