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Open House | Wood Burning Fireplaces

Ask This Old House mason Mark McCullough explains what to understand when buying a home with a wood burning fireplace

What to look for

1. Examine the back of the firebox. A properly operating fireplace should have a hot white spot in the bottom center of the firebox.
2. If there are scattered white spots of soot on the lintel in front of the fireplace, there’s a draft issue that could be caused either by a chimney that’s too short, or by a chimney whose draft is being obstructed somehow.
a. If the chimney is too short, a mason can extend the chimney, though that is a more expensive fix. A cheaper, but temporary fix for this problem would be to crack open a nearby window whenever the fireplace is in use to assist the updraft.
b. If there’s an obstruction, either a chimney sweep or a landscaper/arborist can remove it, depending what and where the obstruction is.
3. Check the chimney for creosote. It’s a shiny, black, tar-like substance that forms when pine is burned in the fireplace and can cause destructive chimney fires.
a. A chimney sweep can come and clean the firebox and flue to remove any creosote.
b. A creosote cleaning log can also be burned to loosen up the creosote, though Mark recommends still hiring a chimney sweep since they can also examine the fireplace for any other potential fireplace hazards.
4. Assess the condition of the flue. Only in rare circumstances does the chimney need to be relined, since code requires all masonry in a chimney to be very thick to prevent stray sparks from causing house fires.

Resources

Besides discussing the general operation of a fireplace, Mark also mentioned burning creosote cleaning logs, which can be found at any home center.