The 10 Major Items of a Real Masonry Fireplace
By: Charles W. Ostrander, Executive Director
This is not an all inclusive list of all requirements to meet Building Codes, but is a primer on major items to help avoid problems
1. THE BASICS
Is the fireplace even drawn on the drawings? Or is there just an arrow calling out a "fireplace"? You should at least have the following on the drawings:
2. THICKNESS AND CONSTRUCTION OF FIREBOX WALL (FOR FIRESAFETY)
3. DAMPER CLEARANCE
The metal damper is required to be a minimum of 8" above the top of the fireplace opening. I suggest, to minimize possible excessive smoking, to place the damper an additional 4 inches high for a total of 12" above the fireplace opening. \
4. Chimney Clearances
Any portions of a masonry chimney located in the interior of the building or within the exterior wall of the building shall have a minimum air space clearance to combustibles of 2 inches. Chimneys located entirely outside the exterior walls of the building, including chimneys that pass through the soffit or cornice, shall have a minimum air space clearance of 1 inch. The air space shall not be filled , except to provide fire blocking.
5. Flue liners
Fireplace Chimneys with clay flue liners must be enclosed with 4" of solid masonry. If multiple fireplaces are vented in a common masonry flue stack, each flue should be supported and separated by 4" of masonry from top to bottom, between the flues vertically.(maximum slope of flue is no greater than 30 degrees from vertical.)
6. Hearth Information
Hearth extension (from the front of fireplace opening)
Hearth extension (from each side of opening) 8" if fireplace opening is less than 6 square feet
7. Flue size
I prefer a slightly oversized flue instead of an undersized flue (for initial startup reasons). You can always
damper down the flue opening - but you cannot draw more air once the damper is open 100%. Here are some of the most common fireplace opening / flue sizes:
A. Use outside air for combustion kits built into the hearth with the outside air vents just inside the front of the fireplace. (if air kit is a retrofit or an afterthought, put a circular pipe vent into the back or side wall of the fireplace)
B. Use sealed, glass fireplace doors.
9. For convenience
Install a log lighter, unless you were an Eagle Scout. You'll have more fires and enjoy your fireplace more. Also, install an ash caddy dump into your hearth for ease of ash removal.
10. Install a spark arrestor for your chimney
The major reason in the midwest is to prevent rain from going down your flue and possibly causing a damp
smell - but a good metal chimney cap also prevents Rocky Racoon or a grey squirrel from taking up residence with other associated problems.