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Oct 14, 2023

How to Clean Your Chimney

Gear-obsessed editors choose every product we review. We may earn commission if you buy from a link. Why Trust Us? Do this every year to prevent chimney fires. When the mercury drops, sitting in front

Gear-obsessed editors choose every product we review. We may earn commission if you buy from a link. Why Trust Us?

Do this every year to prevent chimney fires.

When the mercury drops, sitting in front of a roaring fire is a relaxing and comforting way to spend an evening. If you have a wood burning fireplace in your home, you likely enjoy the experience as much as we do. Maintaining a fireplace, though, isn’t nearly as romantic as using one, and an annual cleaning is critical to its safe operation. If you only use your fireplace a few times a year, at a minimum an annual inspection is still in order, to be sure your chimney is both clean and clear.

When a fire burns hot and fast, it consumes most of the available fuel, and the heat and smoke rises up the chimney quickly. But, when fires burn slowly, they tend to smoke more and expel unburned exhaust gasses which travel up the flue more slowly. These gasses can condense and create deposits of creosote on the chimney liner. Since the creosote is formed from unburned fuel, it is combustible, and can ignite at temperatures as low as 451 degrees Fahrenheit. According to the Chimney Safety Insitute of America (CSIA), as little as a 1/8-inch deposit of creosote is enough to cause a chimney fire.

It might not seem like a big deal to have a bit of fire in your chimney, particularly if it’s made of masonry. But, chimneys and flue liners are designed to contain and direct smoke. They’re not intended to contain the type of intense fire caused by burning creosote. Extreme heat can cause masonry tile liners to crack, and metal liners to warp, potentially exposing combustible materials nearby, like your home’s framing.

Whether you’re doing it yourself, or hiring a professional, the best time to clean your chimney is early fall, around September. At that time of year, professional cleaners won’t yet be too busy. If you plan on doing it yourself, it’s past the worst heat of summer—walking on your roof in the hot sun can damage asphalt shingles. It will also give you time for repairs before heating season, in the event you spot issues during your initial inspection.

Doing it yourself is not necessarily difficult, unless your roof is steep, slippery, or hard to access. If you have any of these issues, or are uneasy about being on the roof, you might want to hire a professional or clean your chimney from inside your house, through the fireplace, from the bottom up—but, know that this can get messy and create a lot of black dust that will be hard to contain with the fireplace open to access the flue.

Typically, you’ll clean your chimney from the roof, or from the top down.

Before you attempt to clean your chimney, you’ll need to perform an inspection. It’s best to do this from both the top and the bottom. Start at the bottom, by cleaning all the ash out of the fireplace and removing any andirons or grates. You’ll need to look up the flue, so put on goggles and a dust mask. Flip your damper open—if you have a masonry fireplace, that will likely be a cast iron handle or loop hanging down from the top of your firebox. If you have a manufactured fireplace, it may be a metal rod or flat strap of metal bent into a hook near the top of the fireplace opening.

With the damper open, you’ll need to look up the flue, scanning for any obstructions—either full or partial—and examine the tile or metal liner. Use a fireplace poker to reach up and scrape at the surface of the liner to see how much creosote is present. If you have 1/8-inch or more, it definitely needs to be cleaned.

To examine from the top, you’ll need to get on the roof, of course. You’ll need a screw or nut driver to remove the chimney cap, a tape measure to check your flue size, and a rope with a weight, to measure your flue height. Chimney caps are usually held on with sheet metal screws with hex heads—sometimes with bolts. Remove the chimney cap and examine the chimney crown and any flashing that may be present. Check for any degradation of mortar that might let water in or otherwise need repair. Look down the flue to check for obvious obstructions and note the flue shape: round, square, or rectangular. Measure the flue diameter or width—you’ll need to know this to get the right chimney brush for cleaning. Finally, measure the flue height by dropping the rope, with a weight on the end, down the chimney, until you feel the weight hit the bottom, and mark the rope. Pull the rope up and put the chimney cap back on.

You can measure the rope once you’re back on the ground. Chimney brushes are pushed down, or up, the chimney with rods connected end-to-end. You need to know the flue height, so you can get the right number of extension rods.

Note: if you do not have a chimney cap of any kind, consider installing one—they keep out both water, and critters that could create blockages with nesting material.

Get a chimney brush to match your flue size and shape. If you have a square 6-inch by 6-inch flue, that’s the size brush you’ll need. For a masonry, tile lined chimney you’ll want a metal chimney brush, for any metal lined chimney, you’ll need a plastic or poly brush. You’ll also need enough chimney brush rods to reach the full length of your flue. The rods and brush usually have ¼-inch threaded ends, one male, one female so they can be connected—make sure the brush and rods you get have matching connectors.

Use one plastic drop cloth to cover the floor in front of your fireplace. Secure it with painters’ tape so it won’t move around while you’re working. Open up the damper and remove it if possible. If you are cleaning the chimney from the top, take a second plastic drop cloth and cover the fireplace opening, taping and sealing it all the way around so that dust and debris doesn’t escape into the room.

If you are cleaning from the bottom up, leave the fireplace open—but you might want to cover furniture and carpets in the room to protect them. If you have a manufactured fireplace with a round metal flue, you’ll need to remove the round damper to be able to get your chimney brush up it. Check the manufacturer’s manual for details on removal—it’s normally just a couple screws or bolts. On some models, you may need to remove the fireplace surround to be able to get into the firebox and access the damper.

Climb up on the roof and remove the chimney cap. Attach your chimney brush to one chimney brush rod and insert it into the flue—it should take a little effort to force it in. Push it down the full length of the rod and pull it back up, repeatedly. With it pushed down, and the end of the rod about just above the top of the flue, attach another rod and repeat the process until you’ve reached the bottom of the flue. You’ll know this when the brush pops out of the flue at the bottom and there is no more resistance when pushing it down. Pull it back up, removing one rod at a time as you do. Visually inspect the flue—if it looks like you’ve scrubbed away the creosote, you’re done. If not, repeat the process. When you’re satisfied, replace the chimney cap.

If you’re cleaning the chimney from the bottom up, the process is basically the same. Although, it’s trickier from the bottom, because you have to bend the rods to get them into the fireplace and then up the flue. If you have a masonry fireplace you also have to pass through the narrow damper. Force the brush up the chimney, one length of rod at a time, pushing it up and down in a scrubbing motion as you go. Eventually, you’ll feel the brush pop out the top of the flue—pull it back down removing the lengths of chimney brush rods as do.

Wait ten to fifteen minutes to let dust settle, before opening up the fireplace. Put on gloves and a dust mask. Remove the plastic slowly, rolling it up into a ball as you go—being sure to keep the dirty side of the plastic on the inside of the ball. Gently scoop up the debris in the fireplace with a dustpan and try to avoid stirring up dust. When you have it as scooped out as clean as possible, use a vacuum to get the fine dust.

If you have a manufactured fireplace, you can jump to step four. If you have a masonry fireplace, you’ll still need to clean inside the smoke chamber.

Reach up into the smoke chamber with the long-handled brush and scrub over the front, back, and both sides. It’s tricky to reach in there, but be as methodical as you can. Some of the debris will fall into the firebox while you’re scrubbing, but a lot of what fell from the flue as well as off the sides of the smoke chamber will fall on a shelf behind the damper. To access that, bend a 90-degree angle in the noodle brush, put it up through the damper and turn it to sweep debris off the shelf. Do this until debris stops falling through the damper. Then, thoroughly clean out the firebox.

Reinstall your damper, and your fireplace surround if you had to remove it. Move all your tools out of the room, roll up the plastic drop cloth on the floor, and replace any andirons or fireplace grates.

That’s it—you’re done.

Brad Ford has spent most of his life using tools to fix, build, or make things. Growing up he worked on a farm, where he learned to weld, repair, and paint equipment. From the farm he went to work at a classic car dealer, repairing and servicing Rolls Royces, Bentleys, and Jaguars. Today, when he's not testing tools or writing for Popular Mechanics, he's busy keeping up with the projects at his old farmhouse in eastern Pennsylvania.

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