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Signs Your Chimney Needs a Checkup

Gathering around a wood-burning fireplace is an irresistible winter ritual, but a fire is still, well, a fire.

Shown: Mason Mark McCullough replaces a damaged brick in a fireplace surround. Changes to stone or marble can also indicate potential trouble.

Even if you stick to the recommended schedule of annual chimney inspections, issues that require a pro’s attention can crop up at any time. Here, some potential problems to look for:

Buckling Brick or Stone

Noticed any cracking or settling of masonry—inside the firebox or anywhere on the surround or hearth? Call in a professional mason before lighting another fire. “Even a small gap can give sparks, cinders, and high heat a direct route to surrounding combustibles,” says chimney safety expert Russ Dimmitt.

Fallen Debris

Crumbly black soot accumulating in your firebox can be a sign that combustible creosote is building up and you’re overdue for a chimney cleaning. Finding what appear to be broken tile or pot shards is even more cause for concern.

An older home with a masonry fireplace may still have a terra-cotta chimney liner; pieces of it in the firebox indicate the liner’s been damaged, likely due to a chimney fire.

“Chimney fires most often occur when something blocking the chimney, like creosote or a bird’s nest, ignites,” says Mark Schaub, a chimney restoration expert who’s worked on many This Old House TV projects. “The resulting burst of heat and rapid change in temperature can crack a terra-cotta liner.”

The cracking will also make a loud noise and push smoke back into the living space. If you suspect you’ve had a chimney fire or you find terra-cotta debris, do not use your fireplace until it’s been inspected by a certified chimney sweep.

Smokey Odors

“You should never smell smoke outside the room the fireplace is in,” says Schaub. “And if the fireplace is working properly, you shouldn’t have an excessive odor there, either.” If you smell smoke beyond what you’re used to when you use your fireplace, extinguish the fire and call 911. Your local fire department will use heat-sensing guns or thermal imaging to pinpoint any danger.

Wall Changes

Heat escaping from cracked masonry, a damaged liner, or an improperly installed prefab metal firebox (most common in newer homes) can cause wood framing to become so dry and charred that it’s capable of igniting at a much lower temperature. How can you tell if there’s excessive heat inside your walls?

Pictures falling off the wall, for example, can indicate that plaster or drywall has overheated and softened, as can bubbling or peeling paint. Any wall changes merit a pro’s attention, says Schaub, who recommends finding a sweep certified by the Chimney Safety Institute of America at csia.org.

Thanks to: Mark Schaub, Chimney Savers. Russ Dimmitt, director of education for the Chimney Safety Institute of America and the National Chimney Sweep Guild.