There’s far more to a masonry (brick) chimney than meets the eye. While some homeowners may be vaguely familiar with a chimney’s interior, we have customers where the only thing they know about a “chimney” is that “this is the place where all the smoke goes out!”. Knowing about these parts and their functions can be useful when talking with a fireplace and chimney professional about a particular problem, service or repair. Use the following guide to understand the various parts of your chimney, and be more informed on your next annual chimney inspection!
The chimney “structure”
1. Chimney Crown – Your chimney crown (top) protects your chimney’s interior from water infiltration that can lead to brick and mortar damage. Remember! The “chimney” that you see on the outside is merely a “shell”. A chimney cannot be made entirely of “solid brick”. (See chimney liner). Even minute amounts of water can result in brick flaking, called (“spalling”), mortar deterioration and unsightly salt deposits on your chimney (efflorescence). Without a properly constructed crown your chimney does not have any rainwater exclusion protection. Eventually, the bricks and mortar become weak enough that the chimney may no longer be structurally sound.
2. Flue – The flue is the passageway or exhaust for conveying the smoke and gases from an appliance to the outside atmosphere. As per most building codes, the liner must be, at least, 1/10th the area of the fireplace opening.
3. Chimney Liner – Same as “Flue”. Sorry! My graphics person messed up. Not to worry, he did not get paid (but I still used the illustration!)
4. Smoke Chamber – The purpose of the smoke chamber is to “funnel” the smoke from the larger width of the fireplace down to match the much smaller chimney liner (or flue).
5. Fireplace Damper – This is a device (normally a metal “plate”) that is opened to facilitate using the fireplace and is closed when not in use to help reduce energy loss.
6. Smoke Shelf – This “shelf” is directly behind the damper. Usually, but not always, a flat area (hence “shelf”, it catches any falling debris and is a pain in the botunkus to sweep!
7. Mantle – Does not have any purpose other than a place to put trophies from the “glory days!” or family photos.
8. Lintel – The metal piece (bar) that is used in the construction of the fireplace to hold the bricks in place until the mortar “cures” or hardens. Does not have anything to do with the functionality of the fireplace or chimney.
9. Throat – The area at the damper where the smoke passes through.
10. Firebox – Where you build the fire silly!
11. Hearth Extension – Normally thought of as the “hearth” (it is not!). This protects the area directly in front of the fireplace from radiant heat, wayward sparks and ash. This is where our dog usually sleeps when our fireplace is in use!
12. Hearth – This is the true “hearth”. It is the bottom of the “firebox”.
13. Ash Dump (Door) – (not a “requirement” and not all fireplaces have them). This is the opening where the ash can be emptied into the ash pit.
14. Ash Pit – Self explanatory!
15. Ash Pit Access (or clean-out) Door – Frequently located outside or in a basement to facilitate removal of the ash when pit gets full.
16. Footing* – See Foundation.
17. Foundation – Where the mason starts! It is the “weight bearing” portion of the structure. If the chimney starts to “pull away” from the house, it is due to the lack of a properly installed foundation.