ANATOMY OF A FIREPLACE
1. Chimney Cap/Spark Arrestor
The purpose of a cap with a spark arrestor is to prevent the entry of rain, animals, and debris while freely allowing the exhaust to exit the home through the chimney flue.
2. Chimney Crown Cap
The crown cap is the protective “helmet” to your masonry chimney. Its job is to shed rain, debris and stop cold air from coming down the brickwork of your fireplaces’ chimney.
3. Height
The height of a chimney is a critical element to your home’s heating system.
If the chimney top is too close to the roof, sparks can catch nearby combustibles on fire. Chimneys should be at least 10-feet in overall height. Where it projects above the roof, the chimney should be at least 3-feet tall, and at least 2-feet higher than anything within 10-feet.
4. Brick and Mortar
Brick and mortar are used to construct a chimneys’ outer walls. Due to time and changing seasons, your brick chimney will develop spalling bricks and require tuck-pointing repairs after a few years.
5. Fireplace Flue Liner
The fireplace flue liner carries exhaust from your fireplace (or furnace flue) to the outdoors. A defective flue liner will hinder the draft of your fireplace and may allow heat, fire, and/or fumes to reach your home.
6. Gas Chimneys for Furnace & Water Heater Flues
Gas furnace and water heaters exhaust through a flue vent similar to the liner in your fireplace. The gas exhaust contains carbon monoxide and is extremely hazardous to your health, and exposure can even be fatal.
7. Flashing
Your chimney’s flashing prevents water from entering your home through the roof. It’s built using a thin layer of sheet metal to protect against rain or moisture. This layer is applied at joints where the chimney meets the roof, shoulder, etc. Loose or leaky flashing causes extensive damage, often without the homeowner noticing. We find water stains on ceilings to be one major sign of chimney leak damage.
8. Firestops
Every home’s fireplace system should firestops built-in. You may not be able to see all firestops but are required to prevent a home fire from passing through a horizontal surface (ceiling, floor, etc.) through the next level.
9. Minimal Clearance
Because the outer surface of chimneys can become hot, the minimum clearance required between the exterior of the chimney and combustible construction is 1-4 inches.
10. Wythe
When a chimney contains more than one flue, a wythe (vertical section of interior masonry wall) should separate the flues from one another.
11. Flue Offsets
If a flue must change directions in its path through a chimney, the offset can not be more than the center of the upper portion exceeding the lower flue’s wall. (nfpa211 7.1.2)
12. Mantel
A decorative shelf added safely above the firebox opening is called the fireplace mantle. It’s one of the most commonly recognizable fireplace features and is one part of the fireplace surround. Mantels must be far enough away from the top of your fire, to avoid overheating.
13. Smoke Chamber
A pyramid-shaped transition, to provide a seamless passageway between the firebox and the beginning of the fireplace’s chimney liner is called the smoke chamber.
14. Damper
A The fireplace damper is a door or valve used to control the draft of an open fireplace.
15. Glass or Screen Door
Glass or fireplace screen doors help control the spill of smoke and sparks from the burning flames. The screen or glass doors should be functional and appropriate for the size and type of fireplace you have (and contrary to popular belief are not a one-size-fits-all accessory).
16. Firebox
A fireplace’s firebox is built of non-combustible/heat rated firebrick and refractory mortars and be of adequate dimensions, to have a functional ratio with the flue liner.
17. Firewood Grate
A firewood grate is a strong metal device for holding logs off the floor of a firebox, to promote air circulation with fuel, during the fire.
18. Hearth Extension
A fireplace hearth extension is the brick pad, directly in front of the firebox opening. The outer hearth is entirely supported by the chimney, at least 4-inches thick.
19. Ash Dump
A chamber dedicated to the deposits of ash from the firebox. Must be constructed of non-combustible masonry materials.
20. Ash Clean-Out Door
A closable, non-combustible metal opening, below the fireplace to allow access to the ash pit. The door is often called the “ash dump”and is used to clean out the ashes from the fireplace.
21. Floor Joist
Floor joists are lumber used build a solid floor that spans an open area, Both support and flooring must not come in contact, nor be supported by the chimney.
22. Appliance Connectors
The connectors are the beginning of the appliance venting system. They bridge the gap between the flue collar of the furnace/water heater and the chimneys’ thimble.
23. Chimney Thimble
The opening in the chimney’s wall for connection of the connectors is called the thimble.
24. Clean-Out Opening
For removal of debris that may enter the chimney. The clean-out opening must be 6-12 inches above the base of the flue.
25. Footings
Footings should extend six inches beyond each side of the brick structure of the chimney. Foundations are a minimum of 12-inches thick.