Creosote Removal for Fireplaces and Flues

Creosote is what is left when wood smoke cools and condenses on the inside of the flue. Light, sooty creosote brushes off. The trouble starts when it builds into a crusty layer or a shiny, tar-like glaze, which is harder to remove and burns far hotter if it ever catches. A chimney fire that starts in glaze can crack clay flue tiles in minutes.

Chicago fireplaces are especially prone to the slow kind of buildup. Most get a few short fires a winter, often with the damper half closed, and the stack itself is cold: O'Hare averages about six and a half nights a year at or below zero, per NOAA's 1991 to 2020 normals. Cold masonry pulls moisture and tar out of the smoke early. The inspection is free, and if heavy creosote is there, the removal is priced before we begin.

Signs you need this

• Shiny black glaze on the flue walls or smoke chamber
• Thick, crusty flakes that a fireplace poker can't scrape off
• A strong tar smell from the fireplace, worse in summer heat
• A past chimney fire, or a roaring sound in the flue at some point
• Puffy, honeycombed deposits after a hot fire

How we do it

1. Inspect and photographWe light and photograph the flue, measure how thick the buildup is and check the tile for cracks.
2. Choose the methodCrusty creosote comes off with rotary tools; glaze may need a chemical treatment first to break it down.
3. Remove and containThe room stays sealed and under a HEPA vacuum while we work the flue, smoke chamber and firebox.
4. Check the tileWith the flue clean we look again for cracks the creosote was hiding, and show you the photos.

Why glaze is the stage to worry about

CSIA says to sweep a masonry flue at about an eighth of an inch of buildup and sooner if glaze is present. Glaze forms when tar-heavy smoke keeps condensing in a cool flue and hardens layer on layer. It is dense, it doesn't brush off, and it is fuel sitting right against the liner.

Taking it off can take more than one visit when it is thick. We would rather tell you that up front than leave a layer behind and call the flue clean.

Bringing the buildup down for next year

Most creosote problems we see come from burning habits, not from the chimney. Small changes help a lot.

• Burn wood that has dried for at least a season, split and stored off the ground
• Let the fire burn hot for the first half hour before closing the damper down
• Avoid overnight smoldering fires with the air nearly shut
• Never burn wrapping paper, cardboard boxes or painted scrap lumber
• Have the flue looked at every year, as NFPA 211 calls for

What if the flue tile is damaged underneath?

Heavy creosote often hides cracked or missing tile, especially in chimneys that have had a fire. If we find damage after removal, you get photos and a written price for the repair or a liner before anything else is done, and you can decide in your own time.