Chimney Sweeping Basics: What, Why, How, When, and How Much.

Updated by Lisa A on January 20, 2019 in

Chimney Cleaning, Chimney Sweeping

What is chimney sweeping?

Chimney sweeping is the process of cleaning the interior of a fireplace flue, usually with specialized brushes, to remove any buildup or obstructions that may hinder air flow or create a fire hazard. Regular chimney sweeping is a critical part of home maintenance and fire safety. A chimney dirtied with buildup is not only inefficient but dangerous. The process should be performed by a skilled technician, ideally one certified by the Chimney Safety Institute of America.


 Chimney Sweep


Why is chimney sweeping necessary?

When you light a fire in your fireplace, as the smoke travels up the chimney, it leaves behind deposits of creosote, a byproduct of combustion. In addition to being highly combustible, creosote buildup also hinders airflow and reduces draft, which is necessary for complete combustion. In its initial stages, creosote is flaky and sooty and thus easily removed with chimney brushes. Over time however, as more fires are burned and more creosote is deposited on top of this initial layer, the buildup becomes thicker, harder, and more difficult to remove. Draft is further reduced, more creosote is deposited, and this process continues until the creosote is removed (or there is a chimney fire). 

In addition to the removal of creosote, routine chimney sweeping will also remove any animal nesting or plant debris that can obstruct the flue and also create a fire hazard. Placing a chimney cap will prevent animal entry, and a savvy chimney sweep will always recommend a cap if one is not present.


How is a chimney swept? 

A chimney can be swept in one of two ways, down through the top of the flue on the roof (top-down), or up through the fireplace (bottom-up). Some companies may perform one method more often than the other due to preference or tech experience, although sometimes the structure of the chimney or fireplace itself will determine which method should be utilized. 

Whether from the top-down or the bottom-up, the tool of choice for chimney sweeping is usually a series of connected flexible rods, adjustable in length to suit the height of the chimney, to which brush heads are attached. One of our technicians swears by the Viper GFK Chimney Cleaning System. The brush heads vary in size to allow for different flue shapes and sizes, and the brush bristles can be made of plastic (generally used in metal-lined flues) or metal (used in clay flue liners). Once inserted into the flue, the brush is moved up and down repeatedly until the creosote or any other debris has been thoroughly loosened and falls to the floor of the firebox, from where it is vacuumed. In cases where creosote buildup is more severe, chains or chemicals may be needed to effectively remove it. 


When should a chimney be swept?

The general recommendation on frequency of chimney sweeping is after every 30-50 fires. Among the factors that affect how frequently it's recommended would be what type of wood you're burning (hardwoods produce less creosote) and how well-seasoned the wood is (the dryer the wood, the less smoke it produces, and thus less creosote). 

Spring is the ideal season to have your chimney swept, for several reasons. This is the slow season for chimney sweeps, so setting an appointment won't be a challenge like it will be as winter approaches. Also, the roof will be free from snow or ice and more easily climbed by the technician if he'll be working (or inspecting) from the rooftop. And finally, if any issues of disrepair are found, you'll have all summer to collect quotes and arrange to have the work completed before fall, when chimney repair technicians are very hard to come by.


How much does a chimney sweep cost?

You can expect to pay between $80 and $200 to have your chimney swept. There are several factors that can affect your final cost. If you choose to have your chimney inspected (especially with a camera), this will likely increase your cost, though some companies include at least a level 1 inspection for no additional charge. If any part of your chimney (or wood stove) requires disassembly in order to effectively sweep it, this too may add to your cost. If you're having more than one fireplace cleaned (which would mean more than one flue), expect to pay more. It is a common misconception among homeowners that two fireplaces that share a chimney will count as one job; it doesn't—no two fireplaces share a flue, and it's the flue that's being swept, after all.

Wanna  dig deeper? Download our free tipsheet: 5 Questions to Ask Before Hiring a Chimney Cleaning Company. 

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Many thanks to our technicians Ben and Kris for lending their expertise to this article.


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