Chimney maintenance 101

Spring is upon us… well, almost. Soon the curbs will be overflowing with winter’s accumulated rubbish as we set about the annual task of spring-cleaning. We’ll open every window and door in our homes to try to banish the stale winter air and dust and let in the warm vernal breeze. Birds singing! Flowers blooming!

The last thing on our minds is the dark, dank chimney. It’s pretty basic, right? Smoke from the furnace goes up and out of it… end of story. And it’s made out of bricks. What can go wrong?

“The most overlooked part of any home is the chimney,” says Denis McGuire, owner of Jiminy Peak Chimney Sweep in Kingston. McGuire has 30 years experience working with chimneys. “I usually don’t get called in until there’s a problem.”


According to NFPA code 211 (National Fire Protection Association), the code pertaining to chimneys and fireplaces, a chimney must be inspected annually. Though this organization is recognized by chimney technicians and fire marshals everywhere as the gold standard, its pronouncements and specifications lack teeth. There’s no “chimney police” to enforce these rules, and there’s no penalty for letting a chimney fall into disrepair. And there can be serious consequences to neglecting chimney maintenance, ranging from greater repair costs down the line to a house-razing structure fire.

With chimneys, like anything that requires maintenance, an ounce of prevention is worth a pound of cure. The reason a chimney has to be inspected and occasionally cleaned has to do with the corrosive and flammable nature of the residue (called creosote) that accumulates on the chimneys inner lining, or flue.

“Under the right conditions, the creosote can ignite, and it burns very hot,” says McGuire. The result, called a chimney fire, is usually contained within the chimney. For some people, this is the first sign that anything can go wrong. Waiting for such a rude wake up call can be dangerous, says McGuire, because if the chimney has been neglected, years of acidic creosote deposits have the potential to destroy the flue and brick structure of the chimney, allowing the extreme heat to ignite the structure of the house around it.

Chimney fires represent the most extreme and explosive consequence of neglect. However, since their destructive power is usually contained and they most often occur in homes with wood burning stoves, they aren’t the most dangerous kind of problem. According to McGuire, that dubious distinction belongs to carbon monoxide poisoning.

The problem, as with out of control chimney fires, lies in the deterioration of the chimneys flue, which, in most chimneys, is made of clay tiles several feet long and of variable thickness. “The flue tiles are your first line of defense,” says McGuire. “Without them, carbon monoxide can escape through the bricks, which are more porous than the flue tiles. Once you get to the bricks, you have a joint every few inches instead of feet.”

“Any home with a chimney, and that’s any home using anything but an all electric heating system, needs a carbon monoxide detector,” he added.

As it turns out, this is the best time of year to get your chimney inspected. For one thing, since most people who do have the sense to call a chimney sweep usually wait until the fall, it’s much easier to schedule an appointment. If you need work done, spring is ideal for several reasons. Two of the main services chimney sweeps usually provide (installing caps and crown washes) serve to keep rain, animals, and anything else out of your chimney, so it’s best to get them taken care of before the spring rains. If your chimney needs to be cleaned, getting it done now would increase the value of the service to the chimney, says McGuire. “The humidity of the summer accelerates condensation within the chimney. (That moisture) speeds up corrosion.” Temperature differential is another factor. The closer the temperature within your home is to the temperature outside, the lesser the airflow coming through the chimney. Less airflow means less chimney stink wafting around your home.

A few more necessary pieces of chimney knowledge: if you have an older chimney, with clay flue tiles hooked up to a high efficiency gas or oil furnace, you’re inviting disaster. “Modern high efficiency furnaces will destroy flue tiles within a year,” says McGuire. Because the stack temperature is so cool (due to more heat from the furnace staying in the house), much more condensation occurs, accelerating corrosion. For this reason, McGuire uses stainless steel liners exclusively. If your chimney is stainless steel, you still need to have it serviced, but you’ve got an advantage over most, owing to stainless steel’s immunity from corrosion.