|Hearth slab thickness||A||4″|
(each side of opening)
|B||8″ fireplace opening < 6 square foot.
12″ fireplace opening ≥ 6 square foot.
(front of opening)
|C||16″ fireplace opening<6 square foot.
20″ fireplace opening ≥ 6 square foot.
|Hearth slab reinforcing||D||Reinforced to carry its own weight and all imposed loads.|
|Thickness of wall of firebox||E||10″ solid brick or 8″ where a firebrick lining is used.
Joints in firebrick 1/4 maximum.
|Distance from top of opening to throat||F||8″|
|Smoke chamber wall thickness
|H||Four No. 4 full-length bars for chimney up to 40″ wide.
Add two No. 4 bars for each additional 40″ or fraction of width or each additional flue.
|Horizontal reinforcing||J||1/4″ ties at 18″ and two ties at each bend in vertical steel.|
|Bond beams||K||No specified requirements.|
|Fireplace lintel||L||Noncombustible material.|
|Chimney walls with flue lining||M||Solid masonry units or hollow masonry units grouted solid with not less than 4-inch nominal thickness.|
|Distances between adjacent flues||-||See Section R1003.13.|
|Effective flue area (based on area of fireplace opening)||P||See Section R1003.15.|
See Sections R1001.11 and R1003.18.
See Section R1001.11, Exception 4.
3' at roof line and 2' at 10'.
Embedment into chimney
3/16″ X 1″
12″ hooked around outer bar with 6″ extension
Two 1/2″ diameter.
6″ each side of fireplace wall.
Note: This table provides a summary of major requirements for the construction of masonry chimneys and fireplaces. Letter references are to Figure R1001.1, which shows examples of typical construction. This table does not cover all requirements, nor does it cover all aspects of the indicated requirements. For the actual mandatory requirements of the code, see the indicated section of text.
- The letters refer to Figure R1001.1
- Not required in Seismic Design Category A, B or C.
- Masonry fireplaces listed and labeled for use in contact with combustibles in accordance with UL 127 and installed in accordance with the manufacturer's instructions are permitted to have combustible material in contact with their exterior surfaces.
- Where masonry fireplaces are part of masonry or concrete walls, combustible materials shall not be in contact with the masonry or concrete walls less than 12 inches (306 mm) from the inside surface of the nearest firebox lining.
- Exposed combustible trim and the edges of sheathing materials such as wood siding, flooring and gypsum board shall be permitted to abut the masonry fireplace sidewalls and hearth extension in accordance with Figure R1001.11, provided such combustible trim or sheathing is not less than 12 inches (305 mm) from the inside surface of the nearest firebox lining.
- Exposed combustible mantels or trim may be placed directly on the masonry fireplace front surrounding the fireplace opening providing such combustible materials are not placed within 6 inches (152 mm) of a fireplace opening. Combustible material within 12 inches (306 mm) of the fireplace opening shall not project more than 1/8 inch (3 mm) for each 1-inch (25 mm) distance from such an opening.
- When the masonry heater wall is at least 8 inches (203 mm) thick of solid masonry and the wall of the heat exchange channels is at least 5 inches (127 mm) thick of solid masonry, combustible materials shall not be placed within 4 inches (102 mm) of the outside surface of a masonry heater. A clearance of at least 8 inches (203 mm) shall be provided between the gas-tight capping slab of the heater and a combustible ceiling.
- Masonry heaters listed and labeled in accordance with UL 1482 may be installed in accordance with the listing specifications and the manufacturer's written instructions.
The cap shall be a minimum of 2″ (51 mm) thick at the outer edge and overhang the outer wall of the chimney by a minimum of 2″ (51 mm). The drip slot shall be located not less than 1-1/2″ (38 mm) from the outer surface of the chimney. A bond break shall be installed between the concrete cap and the chimney masonry.
Metal caps shall lap down the chimney wall a minimum of 4″ (102 mm) and be sealed with a suitable sealant.
Joint sealants shall meet ASTM C920, type S or M, grade NS, class 25 and be installed in accordance with the manufacturer's installation instructions.
- The net free area of the arrestor shall be not less than four times the net free area of the outlet of the chimney flue it serves.
- The arrestor screen shall have heat and corrosion resistance equivalent to 19-gage galvanized steel or 24-gage stainless steel.
- Openings shall not permit the passage of spheres having a diameter greater than 1/2 inch (12.7 mm) nor block the passage of spheres having a diameter less than 3/8 inch (9.5 mm).
- The spark arrestor shall be accessible for cleaning and the screen or chimney cap shall be removable to allow for cleaning of the chimney flue.
- Clay flue lining complying with the requirements of ASTM C315.
- Listed and labeled chimney lining systems complying with UL 1777.
- Factory-built chimneys or chimney units listed for installation within masonry chimneys.
- Other approved materials that will resist corrosion, erosion, softening or cracking from flue gases and condensate at temperatures up to 1,800°F (982°C).
THIS CHIMNEY FLUE IS FOR USE ONLY WITH [TYPE OR CATEGORY OF APPLIANCE] APPLIANCES THAT BURN [TYPE OF FUEL]. DO NOT CONNECT OTHER TYPES OF APPLIANCES.
Clay flue liners shall be laid in medium-duty water insoluble refractory mortar conforming to ASTM C199 with tight mortar joints left smooth on the inside and installed to maintain an airspace or insulation not to exceed the thickness of the flue liner separating the flue liners from the interior face of the chimney masonry walls. Flue liners shall be supported on all sides. Only enough mortar shall be placed to make the joint and hold the liners in position.
|FLUE SIZE, INSIDE DIAMETER
For SI: 1 inch= 25.4 mm, 1 square inch= 645.16 mm2.
- Flue sizes are based on ASTM C315.
|FLUE SIZE, OUTSIDE NOMINAL
|4.5 X 8.5||23|
|4.5 X 13||34|
|8 x 8||42|
|8.5 X 8.5||49|
|8 X 12||67|
|8.5 X 13||76|
|12 X 12||102|
|8.5 X 18||101|
|13 X 13||127|
|12 X 16||131|
|13 X 18||173|
|16 X 16||181|
|16 X 20||222|
|18 X 18||223|
|20 X 20||298|
|20 X 24||335|
|24 X 24||431|
- Masonry chimneys equipped with a chimney lining system listed and labeled for use in chimneys in contact with combustibles in accordance with UL 1777 and installed in accordance with the manufacturer's instructions are permitted to have combustible material in contact with their exterior surfaces.
- Where masonry chimneys are constructed as part of masonry or concrete walls, combustible materials shall not be in contact with the masonry or concrete wall less than 12 inches (305 mm) from the inside surface of the nearest flue lining.
- Exposed combustibl e trim and the edges of sheath ing materials, such as wood siding and flooring, shall be permitted to abut the masonry chimney side walls, in accordance with Figure R1003.18, provided such combustible trim or sheathing is not less than 8 inches (203 mm) from the inside surface of the nearest flue lining.
|12 - 12||1/2 of W|
|8 - 12||1/3 of W|
|6 - 12||1/4 of W|
|4 - 12||1/6 of W|
|3 - 12||1/8 of W|
Chimneys for use with open combustion chamber appliances installed in buildings other than dwelling units shall comply with the requirements of UL 103 and shall be marked "Building Heating Appliance Chimney" or "Residential Type and Building Heating Appliance Chimney."