It's a common enough occurrence, but that doesn't make it any less weird, or annoying: animals nesting in the chimney. Our techs report that 95% of the time they find animals (or evidence of animals) in a chimney, it's because the chimney is missing a cap. Priced starting around $150 with installation, a chimney cap is a minimal investment and can save you lots of headache (and time spent running around your house ridiculously with a net).
Why do animals nest in chimneys?
Many different species of animals seek the warmth and protection a chimney offers, so they find themselves going down a flue that they sometimes can't get out of. In Minnesota, squirrels seem to be the most common visitors. Many a chimney sweep has witnessed squirrels scampering up and down the roof, disappearing into the chimney with a mouthful of flue-clogging foliage, reappearing shortly thereafter empty-mouthed. Birds perform a similar disappearing act. This nesting debris (and in some cases the carcass of the animal itself), can quickly clog the flue and create a fire hazard.
Sometimes a determined animal can gain access to your chimney even with a cap in place, especially if the cap is low-quality or jerry-rigged. In a recent case, our technician Ben noted that a homeowner had fashioned a custom cap using cheap chicken wire over the top of the flue, with a metal band holding it in place. An animal had managed to peel back the chicken wire and gain access to the flue. Inside, our tech found a mother squirrel and four babies. Normally, if the animal is alive, the tech will advise customers to call an animal control or pest removal specialist, but they can sometimes tackle easier cases at their own discretion. In this case, with the homeowner's permission, the technician used a coffee table and some other small/portable pieces of furniture to build a pathway toward the front door. Fortunately, the rodent family quickly took him up on his invitation and scurried out the front door!
The worst-case scenario (for the critter)
Of course, it's not always this easy. In many cases the animal cannot make it out the same way it came in and becomes trapped and dies, which can quickly cause odors and attract insects. Again, depending on the chimney sweeping technician, some will tackle this, and others are reluctant and will suggest an exterminator. (Strangely enough, our techs report that many customers say that when they called an exterminator, the exterminator suggested the customer contact a chimney sweep!) In another recent case, our technician showed up at a house with a fireplace infested with flies. The fireplace damper was stuck, and when the tech removed it—with much difficulty—a dead raccoon serving as a host for maggots was discovered on the smoke shelf. Needless to say, after removal and cleanup, the customer happily purchased a chimney cap.
Factors that affect cost
The scope of animal/nest-removal jobs varies widely, depending on the size of the animal, how long it has been there, the type of flue/fireplace, etc. Sometimes the job is relatively straightforward and the carcass is located in an easily accessible portion of the flue. Other times, as in the case of the raccoon, if the animal is large, the damper may have to be removed in order to get to it. On the farthest end of the job-difficulty spectrum, if you have a Heatilator fireplace, the technician would have to take apart the entire faceplate, remove the Heatilator, disconnect the fan, and then remove the damper to get to the animal.
Because of the wide gamut of animal removal jobs that crop up, and the troubleshooting often necessary to resolve them, it is extremely unlikely that a company will quote you a price over the phone. More often than not, they will send a technician out to assess the job and then quote you a price (or price range) to carry it out.
Even if you are lucky enough that your animal guest voluntarily vacates the hospitable setting of your flue, the nesting materials that made it hospitable can be quite troublesome to remove. Our techs report that with some of the larger or longstanding nests, they become so impacted that a poker must be used to dislodge the majority of it, often in a single chunk. In some cases, the nest needs to be "pushed" down from the rooftop, with a few strategic blows, once the cap has been removed. Then they can use a hard steel-wire brush, about 2 inches wider than the width of the chimney, to complete the job.
Don't forget the utility flue!
Sometimes, though not as often (because it is smaller and emits CO), animals take up residence in the utility (furnace/boiler/water heater) flue. When this flue becomes clogged with animals or nesting debris, it is especially dangerous, as these flues carry carbon monoxide from the appliance to the outside, and when they are obstructed, these noxious gases could back up into your living space. A type B gas vent cap, by preventing animal entry, can help avert a very dangerous situation.
Long story short in eight words? Protect wildlife, and your chimney: get a cap!
Wanna dig deeper? Download our free tipsheet: 5 Questions to Ask Before Hiring a Chimney Cleaning Company.
Many thanks to our technicians Ben S and Dave C for lending their expertise to this article.