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Parts of a Chimney 

For many homeowners, chimneys aren’t much more than an attractive architectural element.  Aside from understanding a fireplace needs a chimney; a chimney’s inner-workings and over-all anatomy are uncharted territory for most.

Here is the basic structural anatomy of a masonry chimney and fireplace:

Chimney Cap: A chimney cap prevents water from entering the flue and other components of your chimney.  Most caps are equipped with a mesh barrier known as a spark arrestor.  This barrier inhibits critters from entering and building flammable nests in your chimney.  It also prevents hot embers from exiting and potentially causing an accidental fire.

Cement Crown: The purpose of a crown is to protect the bricks and other structural elements of a chimney from water and moisture, which can enter through small cracks. Cement is more impervious to moisture, so properly constructed chimney crowns are made of cement rather than masonry mortar. Often, crowns are shaped to direct rainwater down and away from the flue.

Chimney Chase: This is the exterior structure of your chimney.  Typically, it’s constructed with bricks or stone and held together by mortar. This portion of the structure tends to be the most familiar chimney component.

Flue: The interior chamber of a chimney through which fireplace smoke and other fumes exit.

Flue Liner:  Also referred to as a chimney liner, this chimney component lines the flue and protects the structure’s masonry components.  Flue liners are either cast in-place or made of metal or ceramic.

Flashing: Flashing provides a waterproof seal between where the roof and the chimney meet.  Typically made of metal, flashing is designed to allow the differing materials used in roofing to expand and contract at their respective rates while maintaining a watertight seal between the roof and chimney structures.

Smoke Chamber: The smoke chamber gently compresses gases and by-products of burning before they exit through the narrower flue.  This compression prevents a backdraft of these harmful substances from polluting the air inside a home.

Fireplace Damper: A damper is essentially a door from the fireplace to the chimney. It allows smoke, debris, and gases from your fireplace to exit the home.  It’s recommended to close the damper when your fireplace is not in use to prevent heat from escaping and cold air from entering.

Firebox:  Also called the fireplace, a firebox is the area where a fire is constructed or housed.  This structure should be lined with firebrick and inspected by a professional regularly for cracks or damage.

Hearth & Hearth Extension: The hearth is the floor of your fireplace where your fire burns.  This structure is constructed to handle high heat and the corrosive by-products of burning.  The hearth extension is the space just outside of the firebox made of a heat resistance material like brick or tile. The extension reduces the likelihood of an accidental fire caused by sparking embers.

Fireplace Face:  This is the aesthetic structure of a fireplace that surrounds the fireplace box and extends to the mantle.  Typically, the face is constructed out of stone or brick.

Foundation:  This is the lowest part of the fireplace walls.  It comprises the base of the firebox structure and extends below ground to provide a structural base for the entire fireplace and chimney. It is made of a cinder blocks or heavy-duty bricks.

Having a basic understanding of how the structures and components of your home function is a smart idea for any homeowner.  Hopefully, these terms demystify the internal chimney structure and aid your understanding of its function and proper maintenance when communicating with chimney professionals. Now, the next time you enjoy a crackling fire with family or friends, you will know there is more occurring than meets the eye!

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