Raccoons, squirrels, birds, bats — at some point or another, you may encounter any one of these critters in your chimney. Their presence can disturb your living space, cause costly damage to your chimney or fireplace, and at worst, curious or frightened wildlife may find its way into the rest of your home.
HY-C’s HY-Guard exclusion products have been protecting homes from nuisance wildlife for decades, and our chimney caps have been on top of flues for over 75 years. In the category of keeping animals out of chimneys, there’s nothing we haven’t seen.
In this guide, we’ll outline how a chimney works, which animals get into them, and how they manage to sneak in. We’ll also explain how a good chimney cap can go a long way towards keeping critters out of your chimney to help you keep your chimney — and your home — protected.
Parts of a Chimney
It’s important to visualize the components that make up your chimney so you can see both where critters get in and where they set up camp. A traditional fireplace is made up of several components, including the firebox, a damper, a smoke shelf, a smoke chamber, the masonry, and a flue. A standard chimney typically looks something like this:
The firebox is what you see when you look into a fireplace from inside your home. Lined with firebrick, it’s where you burn the wood in your fireplace. The damper is an adjustable steel or cast iron plate at the top of the firebox, and its job is to regulate airflow through the firebox, into the smoke chamber, and up through the chimney. Behind the damper sits the smoke shelf — a flat area at the base of the smoke chamber designed to prevent reverse airflow (i.e., backdrafts) into the firebox. The smoke shelf also helps to protect the firebox from water, debris, or wildlife that makes its way down the chimney.
Atop the smoke chamber, the flue is the exit from which smoke and hot gas escape the chimney. It’s supported by the masonry of the chimney and it extends upward through the building, through the roofline, and ends at some level above the shingles.
The flue is the most common entry point wildlife uses to get inside a chimney, either intentionally to create a nest or by accidentally falling in. Critters may also enter the actual chimney structure through flaws in the masonry, missing mortar joints, or other external damage. Smaller wildlife can get in through openings at the base of the chimney if the flashing is faulty. Decay and extensive weathering on older chimneys may offer still more points of entry for local fauna.
What Kind of Wildlife Gets into a Chimney?
Raccoons are infamous for using the chimney as a maternal den site; a female raccoon can easily climb up and down the inside of a flue. Normally, a mother raccoon births her babies (called “kits”) on the smoke shelf of a fireplace, so that should be the first place you check if you hear critters in your chimney.
Squirrels, bats, and birds can also get into the flue. Unlike raccoons, squirrels can’t climb back up the slick flue tile, and bats and birds have trouble navigating the narrow smoke chamber. Chimney swifts are a notable exception, though. These aptly named birds can fly vertically and have no issues making their home in a chimney. Swifts are protected by the Migratory Bird Treaty Act of 1918 and require special permits for removal.
In some cases, small animals might be able to enter through the cracks and crevices in the masonry or flue tiles. These infestations — usually flying squirrels or bats — are sometimes hard to recognize, but typically easy to exclude with regular maintenance.
What Are the Signs of Wildlife in Your Chimney?
There are two sure signs of wildlife inside a chimney: noises and odors. Noises like scratching, clawing, or just general movement indicate that there may be an animal on top of the damper or the smoke shelf. If the damper was left open, the culprit will likely be staring you in the face from your firebox (or even running around your living room). Chirps or chittering are usually indicative of birds or raccoons.
Odor normally suggests raccoons as well, but most homeowners can pick up the scent of a long-term bird roost and the droppings that come with it. If the odor is particularly foul, the critter may not have survived its time in your chimney. In this case, your priority shifts from animal capture to carcass removal.
How to Inspect Your Chimney for Wildlife
Starting an inspection is easy enough; all you need is a flashlight to peek into the firebox to check for wildlife. Inspecting the smoke shelf is a little more difficult. Visual access to the shelf is difficult, so you’ll need both a light and a camera. From the roof, you can use a strong light source and look down the chimney flue for critters, or you can lower a camera down the flue and play the footage back later. It’s important to note that we do not recommend climbing onto your roof. Leave all roof-level inspections to a professional wildlife control operator.
As the flue is being inspected for wildlife and nesting material, be sure to inspect the chimney itself for any signs of damage, blockage, cracks, weathering, or creosote buildup. Repairing these problems will not only keep future wildlife from getting in, but will also ensure an efficient chimney that functions properly. To really keep wildlife out of your chimney, though, nothing beats a top-of-the-line chimney cap.
How a Chimney Cap Can Keep Wildlife out of Your Chimney
If you don’t have a chimney cap, getting one is an absolute necessity. First and foremost, they keep animals and debris from entering the chimney flue and creating blockages and fire hazards. They also prevent downdrafts and rainwater from getting into the chimney flue.
A chimney cap can also improve the chimney’s draft, helping it to vent smoke and gas more easily. Caps made from galvanized steel, stainless steel, or copper are popular choices because they are aesthetically pleasing, and because nuisance wildlife can’t gnaw through them or rip them off the flue.
It’s important to consider the mesh size of your chimney cap, too. ¾” mesh is common on most caps, but homes in some parts of Oregon and California require ⅝” mesh by law (to stop sparks from escaping and causing forest fires). Mesh size is a balancing act; the mesh needs to be small enough to prevent small animals from accessing the flue, but large enough to allow smoke and gas to escape to stop creosote from building up or ice from forming.
Keep Wildlife out of Your Chimney
The idea of an unwelcome animal making a home in your chimney is unsettling. By now, though, you understand how your chimney works, what kind of animals tend to get into it, how to check for those animals, and how to keep them from accessing your flue in the future.
The best thing to do now is to find the right chimney cap with the best functions and the right aesthetic for your home. Once it’s in place, you won’t have to worry about a family of raccoons living on your smoke shelf anymore.