Hidden chimney damage can turn cozy fires dangerous

MOSES LAKE — The weather is getting chillier, which means lots of people are getting ready to build the first fire of the year in their fireplace. Here in the Columbia Basin where electricity is plentiful, few homes are heated with burnable fuel like wood or oil. But even chimneys attached to fireplaces that only get occasional use should be checked regularly, said Joe Ochal, CEO of Chimney Scientists.

“Chimneys last about 20-30 years before the interior of them starts to degrade and they have holes where heat can transfer into the wall cavity,” Ochal said. “When we’re going into people’s homes and do a chimney cleaning, we put a camera in the chimney every time to make sure there’s no holes where there’s heat transfer. People will often say to us, ‘Well, it’s been this way for 80 years,' and (they’re) surprised that chimneys require maintenance.”

Every chimney should be inspected visually at least once a year, according to the National Fire Protection Agency, and if there’s major remodeling, damage, or the home is changing hands, it should be checked out with a camera as well. The camera can look at a right angle at the side of the chimney, while a visual inspection alone can only look straight up or down, Ochal said. 

The deteriorating mortar between the bricks in a chimney can create a fire hazard, Ochal explained, because the heat moves from inside the chimney through the holes in the mortar into the wood of the house. Repeated exposure over time to that heat can actually lower the combustion temperature of the wood in a process called pyrolysis, according to the U.S. Forest Service, setting the home up to catch fire from leaking chimney heat.

“It’s not just that there’s a hole inside the chimney structure that’s touching or near wood framing,” Ochal said.  “Very often the wood framing that’s holding on your drywall is nailed into the masonry (of the chimney), and the nails are conductors of heat. So as you’re having fires, those nails are heating up the wood over and over and over again.”

Fire isn’t the only problem that can be caused by chimney problems, Ochal said. The flashing that surrounds the base of the chimney on the roof can leak over time as well, causing water damage that might not be immediately visible.

“It’s always good to have the exterior of the chimney looked at to make sure the caulking isn’t falling apart,” he said.