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Chimney Caps

Chimney Caps provide protection from moisture entering your chimney. A chimney without a cap is like a house without a roof.


Without a chimney cap, water entering your chimney collects behind the forebrick causing efflorescence.

Efflorescence in firebrick.


If there were a sixteen inch square hole in your roof, just imagine how much water would enter your home during a heavy down-pour. Chimney flues are typically between eight and 16 inches square, and there are many that are even larger. Why can`t you see the the water? In short, because it`s often absorbed at the base of the chimney right behind a fireplace`s firebrick. Moisture will stay in the chimney for months after a rain-storm, as there is minimal air circulation, sunlight or heat in the chimney unless it`s being used. Evidence that water is getting in, often appears in the form of a rusting damper, or efflorescence on the firebrick or chimney. This moisture when mixed with creosote or ash forms an acid, that only helps to further deteriorate mortar joints, brick, and some stone. Chimneys holding moisture are subject to six months or more of the freeze / thaw cycle here in south west Montana. These are ideal conditions for a deteriorating chimney that will eventually become unsafe for use.


Chimney cap for pre-fab metal chimney

Chimney Cap with spark arrestor.

All chimneys whether serving a fireplace or wood stove should have a chimney cap with spark arrestor. A spark arrestor is a screen, or mesh on the vertical sides of a chimney cap. In the event of a chimney fire, chimney caps with spark arresters will help to reduce the size of the "ball of flames" that sometimes shoot out the top of a chimney. Rather than having a large "ball of flames" land on your roof, the screen disperses the large "ball of flames" into smaller ones that should be out by the time they hit the roof or ground. Chimney Caps with spark arrestors reduce the the risk of a structure fire caused by a chimney fire by approximately 85%.



Custom chimney cap covering 3 chimney flues

Custom Chimney Cap

Several good reasons for installing a quality chimney cap include:

1. Prevent precipitation in the form of snow, rain, or sleet from entering your chimney.

2. Prevent birds and animals from nesting in your chimney.

3. Prevent debris from entering the chimney that could result in a blockage, or chimney fire.

4. Prevent sparks from exiting the chimney that could ignite nearby grass, or other combustibles.

5. Chimney caps with spark arresters reduce the risk of a structure fire caused by a chimney fire by approximately 85% .



Custom Chimney Caps


Big Sky Chimney can install a chimney cap for you. If you need a custom cap, we can have one fabricated. Several options are available for custom caps. Please call 406-995-3385 to discuss options available to you. You can also search our online store for chimney caps.