TABLE R1001.1 SUMMARY OF REQUIREMENTS FOR MASONRY FIREPLACES AND CHIMNEYS
|Hearth slab thickness||A||4"|
|Hearth extension |
(each side of opening)
|B||8" fireplace opening < 6 square foot. |
12" fireplace opening ≥ 6 square foot.
|Hearth extension |
(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.|
|Combustible material||See Sections R1001.11 and R1003.18.|
|Mantel and trim||See Section R1001.11, Exception 4.|
|Above roof||3' at roofline and 2' at 10'.|
|Strap||3/16" × 1"|
|Embedment into chimney||12" hooked around outer bar with 6" extension.|
|Fasten to||4 joists|
|Bolts||Two 1/2" diameter.|
|Width||6" each side of fireplace wall.|
|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 square foot = 0.0929 m2.|
|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.|
|a. The letters refer to Figure R1001.1.|
|b. Not required in Seismic Design Category A, B or C.|
FIGURE R1001.1 FIREPLACE AND CHIMNEY DETAILS
Exception: Rumford fireplaces shall be permitted provided that the depth of the fireplace is not less than 12 inches (305 mm) and not less than one-third of the width of the fireplace opening, that the throat is not less than 12 inches (305 mm) above the lintel and is not less than 1/20 the cross-sectional area of the fireplace opening.
Exception: Where the bottom of the firebox opening is raised not less than 8 inches (203 mm) above the top of the hearth extension, a hearth extension of not less than 3/8-inch-thick (10 mm) brick, concrete, stone, tile or other approved noncombustible material is permitted.
- 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.
FIGURE R1001.11 CLEARANCE FROM COMBUSTIBLES
- Where the masonry heater wall is not less than 8 inches (203 mm) thick of solid masonry and the wall of the heat exchange channels is not less than 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 not less than 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 or CEN 15250 shall be installed in accordance with the listing specifications and the manufacturer's written 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 C 315.
- 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 C 199 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.
Exception: Where venting only one appliance, two flues shall be permitted to adjoin each other in the same chimney with only the flue lining separation between them. The joints of the adjacent flue linings shall be staggered not less than 4 inches (102 mm).
TABLE R1003.14(1) NET CROSS-SECTIONAL AREA OF ROUND FLUE SIZESa
| FLUE SIZE, INSIDE DIAMETER |
| CROSS-SECTIONAL AREA |
|For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2.|
|a. Flue sizes are based on ASTM C 315.|
TABLE R1003.14(2) NET CROSS-SECTIONAL AREA OF SQUARE AND RECTANGULAR FLUE SIZES
| FLUE SIZE, OUTSIDE NOMINAL |
| CROSS-SECTIONAL AREA |
|4.5 × 8.5||23|
|4.5 × 13||34|
|8 × 8||42|
|8.5 × 8.5||49|
|8 × 12||67|
|8.5 × 13||76|
|12 × 12||102|
|8.5 × 18||101|
|13 × 13||127|
|12 × 16||131|
|13 × 18||173|
|16 × 16||181|
|16 × 20||222|
|18 × 18||233|
|20 × 20||298|
|20 × 24||335|
|24 × 24||431|
FIGURE R1003.15.2 FLUE SIZES FOR MASONRY CHIMNEYS
Exception: Chimney flues serving masonry fireplaces where cleaning is possible through the fireplace opening.
- 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 combustible trim and the edges of sheathing 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.
FIGURE R1003.18 CLEARANCE FROM COMBUSTIBLES
TABLE R1003.20 CRICKET DIMENSIONS
|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|
FIGURE R1003.20 CHIMNEY CRICKET
Exception: Chimneys for use with open combustion chamber fireplaces shall comply with the requirements of UL 103 and shall be marked "Residential Type and Building Heating Appliance Chimney."
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."