Chimney Cleaning

Why chimneys need cleaning

Wood smoke cools as it rises. Along the way it leaves soot and creosote on every surface it touches: the firebox walls, the damper, the smoke chamber and the flue lining. Creosote burns. A thick enough layer in the flue is fuel for a chimney fire, and heavy buildup also narrows the passage the smoke needs to get out.

Buildup also holds moisture and acids, which is part of why an uncleaned fireplace often smells in humid weather. Our guide to creosote stages and risk explains the different forms it takes and why some are much harder to remove than others.

Gas fireplaces and furnaces don't make creosote, but their flues can still collect debris, nests and corrosion. Wood is where regular sweeping matters most.

What a complete sweep covers

A quick brush down the flue from the roof leaves a lot behind. The parts that collect the most residue are often the hardest to reach.

The smoke chamber deserves a mention of its own. It sits right above the damper, it's shaped like a funnel, and in many older New Jersey homes its walls are stepped brick that grabs creosote. CSIA notes that a complete sweep should include it.

When it's time for a sweep

The Chimney Safety Institute of America suggests sweeping a masonry fireplace once there is about 1/8 inch of sooty buildup in the flue, and sooner if any glazed creosote is present. Factory-built fireplaces should be swept when any noticeable buildup forms. How fast you reach that point depends on how much you burn, what you burn and how well the system drafts.

Things that tend to speed up buildup:

• Burning wood that hasn't dried long enough (see our firewood guide)
• Small, smoldering fires with the air turned down
• A flue that's too large for the appliance, or an exterior chimney that runs cold
• A wood stove or insert vented into a liner that isn't insulated

Clues that buildup has grown: a strong smoky or tar smell, flakes of black material falling onto the smoke shelf or damper, or a fire that's harder to keep drawing. These are hints, not a diagnosis. The flue itself has to be looked at. For a rough schedule, read how often a chimney should be swept.

How we assess it

Every visit starts with an assessment before any brushes go up. That way the cleaning matches the buildup you actually have, and anything that needs attention is found while the system is open.

1. Ask how you use itWhat you burn, how often, and anything odd you've noticed, like smoke spilling or smells.
2. Look at the firebox, damper and smoke chamberWe note the type and depth of buildup and the condition of the masonry.
3. Camera in the flue where it allowsA chimney camera shows creosote and liner condition in sections a flashlight can't reach.
4. Check the top when it's safeCap, screen and crown, if the roof can be reached safely.
5. Show you the findingsYou get photos of what we saw. If something needs repair, it's explained before any repair is scheduled.

When buildup won't brush off

Light, flaky soot comes off with standard brushes. Hardened, shiny or tar-like creosote does not. That third-stage glaze can need chemical treatment and more than one visit, and sometimes it can't be fully removed. In some cases replacing a liner is more practical than chasing the glaze.

If glazing is present, we'll show you photos and talk through what removal is realistic in your flue before anything is scheduled.

What a cleaning does and doesn't do

A sweep removes fuel for a chimney fire and clears the path for smoke. It does not repair anything. Cracked flue tiles, gaps between tiles, a broken damper or a damaged crown are still there after the brushes come out. That's why the condition of the system is part of every visit.

For gas appliances, oil furnaces and boilers, the residue and the risks are different. See furnace and boiler flue cleaning or gas fireplace service.

What affects the scope

• Number of flues. A chimney that also vents a furnace or water heater has more than one flue to look at.
• Appliance type. A wood stove or insert may need its baffle or connector cleaned too. Our fireplace and wood stove cleaning page covers that work.
• Type of creosote. Glazed buildup takes more time and may need treatment.
• Access. Roof pitch, chimney height and a cap that has to come off all play a part.
• Blockages. Nests or debris add removal time. If an animal is still inside, see chimney animal removal.

Next step

If you use your fireplace or stove regularly and it's been a season or more since the last sweep, it's a good time to book. Tell us what you burn and what you've noticed, and include a photo of the fireplace if you have one. A team member will contact you to confirm a time.

Request a chimney cleaning

Questions homeowners ask

Sources

1. CSIA: Frequently asked questions