Chimney and Fireplace Questions, Answered

The National Fire Protection Association recommends inspecting chimneys, fireplaces and vents once a year. Whether a cleaning is needed depends on what the inspection finds. A common rule of thumb is to sweep when sooty buildup reaches about one-eighth of an inch, or sooner if there is glazed or tar-like deposit. Fires that drift smoke into the room, a stronger smell, or flakes falling onto the damper are all signs your chimney is due for cleaning.

Creosote is the residue left when wood smoke cools and condenses inside the flue. It ranges from loose soot to a hard, shiny glaze, and all forms of it can burn. Heavy buildup is the main fuel in chimney fires. It also narrows the flue, which hurts draft. Burning wet wood, running smoldering fires, and having an oversized flue all speed it up. You can read more about how creosote forms and how it's removed.

The fireplace or stove opening is covered and the floor protected. The flue is brushed from the bottom, the top, or both, with the dust and soot contained. The smoke shelf, damper area and firebox are cleaned as well. Along the way, the sweep looks for cracked flue tiles, damaged mortar, a broken cap, or a damper that doesn't seal, and tells you what they found.

It's a good idea. A general home inspection usually only looks at the parts of a chimney that are easy to see. A dedicated chimney inspection for a home sale looks more closely at the flue, liner, crown, flashing and firebox, so buyers and sellers know about problems before closing rather than after.

A camera lowered into the flue shows what you can't see from the firebox or the roof: cracked or missing flue tiles, gaps in mortar joints, a damaged liner, blockages, and heavy deposits. It's especially useful after a chimney fire, after storm damage, or when smoke or odors have no obvious cause.

The most common entry points are flashing that has pulled away where the chimney meets the roof, a cracked crown, a missing or damaged cap, and brick or mortar that has started absorbing water. Stains on the ceiling or wall near the chimney, rust on the damper, or water in the firebox all point to a leak. Finding the exact source matters, because sealing the wrong spot won't stop it. Our page on tracking down and fixing chimney leaks goes into more detail.

Don't light a fire, and don't try to smoke the animal out. Keep the damper and any fireplace doors closed so it can't get into the house, then call. Afterward, a properly fitted cap with an animal screen keeps the problem from coming back. Our guide to safely getting animals out of a chimney explains what to expect.

Yes. Gas fireplaces don't build up creosote, but they still need attention. The burner and pilot assembly can get dirty, ceramic logs can shift or break down, the glass can film over, and vents can be blocked by nests or debris. A yearly check before the heating season covers these. See our page on gas fireplace maintenance for what a service visit includes.

Humid air reacts with creosote in the flue and produces a sour, smoky smell. When the house pulls air down the chimney, the smell spreads into the room. Debris, leaves, or an animal or nest in the flue can cause odors too. A cleaning usually helps, and a well-sealing damper and a cap with a screen can cut down on both the moisture and the downdraft.

Watch for these signs: clothes take more than one cycle to dry, the dryer or laundry room gets unusually hot, the outside flap barely opens when the dryer runs, lint collects around the exterior hood, or you notice a burning smell. If you smell burning, turn the dryer off and unplug it until the vent is checked. Long vent runs, roof vents and runs with many bends clog faster. Our page on professional dryer vent cleaning explains how lint is removed and how airflow is checked.

The liner protects the surrounding brick and framing from heat and from corrosive exhaust, and it keeps the flue the right size for good draft. A liner may need repair or replacement if tiles are cracked or missing, if you're installing an insert or stove, or if you're switching fuels. An inspection, often with a camera, shows whether yours is sound.

That depends on what the inspection finds, how the chimney is built, and how hard it is to reach. We don't quote prices without seeing the job, but estimates are free, so you'll know the scope before you commit. Our guide on what goes into the cost of a chimney sweep explains what affects the total.