Common Chimney Blockages


This probably sounds obvious, but in order for your chimney to work properly — ushering heat and potentially dangerous gases up from your firebox, out of your home — you need to have a clean and clear flue opening. Gases can move over and around some obstructions, but even in the best cases, that’s not a recipe for efficient flow — and inefficiency in your chimney always brings negative results.

If your flue opening is narrowed by blockages, draft gets impeded, and that can bring a variety of different results — from smoke and smells to much more serious concerns, like toxic carbon monoxide leakage, or heat building up to a point where built-up creosote can ignite and cause a chimney fire.

Ace Chimney Sweeps (and chimney industry groups from the Chimney Safety Institute of America to the National Fireplace Institute) highly recommend having your chimney inspected each and every year and swept regularly, and keeping a clear flue is part of why. Regular chimney sweeping keeps creosote build-up well managed, and annual inspections allow Ace Chimney Sweeps technicians to keep you aware of any current or potential issues that could be impeding your chimney’s function — including flue blockages.

A Few Of The Blockage Culprits We See Most

Chimney blockages can come in many different forms — here are a few of the common contributors:

Critters like this can make your chimney their home and cause blockages. There are also other things that can block your flue. See to it that your chimney is inspected and cleaned regularly to avoid bigger problems from surfacing.

Critters like this can make your chimney their home and cause blockages. There are also other things that can block your flue. See to it that your chimney is inspected and cleaned regularly to avoid bigger problems from surfacing.

Creosote Build-up

Every time you use your wood-burning fireplace or stove, combustion byproducts rise in your flue, and as gases condense on your comparatively cooler flue walls, creosote is created. More creosote layers with every use, and before long, you’ll have a thick creosote coating. The thicker that build-up becomes, the more it affects your draft; the more your draft is impeded, the less efficient your chimney’s function becomes, and the more creosote is deposited; the more creosote you have, the greater chance of a fire hazard, too.

There are smart burning practices you can use to help limit creosote build-up (including making sure you’re only burning fully dried cordwood and keeping your damper all the way open every time you burn), but there’s no substitute for regular chimney sweeping.

Falling Debris

If your flue isn’t covered by a chimney cap, it’s not uncommon for materials to fall into the chimney, causing a blockage. More often than not, falling debris is highly combustible — like brush, twigs and leaves — which makes that blockage doubly dangerous.

Outside materials aren’t the only falling debris you need to concern yourself with, either. Cracked clay flue liner tiles can break, fall and pile up in the flue, causing blockage. Damaged chimney masonry can do the same thing. (A chimney inspection lets us catch cracks and damage like that before it can get that bad, and make the proper repairs to avoid further problems.)

Nesting Animals

To roaming squirrels, raccoons, birds and other animals, your chimney looks like a protected, warm place to live. If those animals get the opportunity to move in, they’ll take it, often carrying in flammable materials to build nests and blocking off your flue in the process. And that’s just one of the difficulties that comes with nesting animals — unwanted smells, bugs, noises and other frustrations tend to come along too.

Avoid Chimney Blockages By Protection Your Flue Opening

A flue that’s wide open at the top is inviting in animals, debris and blockages. That’s among the many reasons we recommend that all of our clients have a properly sized and properly installed chimney cap in place .

A well-made chimney cap will not only keep rain, sleet and snow from getting into your flue and causing water damage, it’ll also close off the flue to nesting animals and falling leaves, branches, twigs and other types of debris.

Top-sealing chimney dampers are another great way to put a “no vacancy” sign up for animals and block the entry of other kinds of debris. Unlike throat dampers, which sit down above the firebox, top-sealing dampers are installed at the very top of the flue, completely closing off the opening with a tight-sealing gasket. Not only are you keeping moisture and debris out with these, you’re also contributing to better energy efficiency — studies have shown these to be anywhere from 75 to 90 percent more efficient at limiting air transference than throat dampers.

Protection with either a chimney cap or top-sealing chimney damper will make the likelihood of chimney blockage that much less, and make your life as a homeowner that much easier.

Do you have any other questions or concerns about chimney blockage? We’re always here to help. Just give Ace Chimney Sweeps a call!