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Section M1805 Masonry and Factory-Built Chimneys

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M1805.1 General
Masonry and factory-built chimneys shall be built and installed in accordance with Sections R1003 and R1005, respectively. Flue lining for masonry chimneys shall comply with Section R1003.11.
M1805.2 Masonry Chimney Connection
A chimney connector shall enter a masonry chimney not less than 6 inches (152 mm) above the bottom of the chimney. Where it is not possible to locate the connector entry not less than 6 inches (152 mm) above the bottom of the chimney flue, a cleanout shall be provided by installing a capped tee in the connector next to the chimney. A connector entering a masonry chimney shall extend through, but not beyond, the wall and shall be flush with the inner face of the liner. Connectors, or thimbles where used, shall be firmly cemented into the masonry.
M1805.3 Size of Chimney Flues
The effective area of a natural draft chimney flue for one appliance shall be not less than the area of the connector to the appliance. The area of chimney flues connected to more than one appliance shall be not less than the area of the largest connector plus 50 percent of the areas of additional chimney connectors.
Exception: Chimney flues serving oil-fired appliances sized in accordance with NFPA 31.
M1805.3.1 Size of Chimney Flue for Solid-Fuel Appliance
Except where otherwise specified in the manufacturer's installation instructions, the cross-sectional area of a flue connected to a solid fuel-burning appliance shall be not less than the area of the flue collar or connector, and not larger than three times the area of the flue collar.

Related Code Sections

Section M1805 Chimneys and Vents, Masonry and Factory-Built Chimneys
Masonry and factory-built chimneys shall be built and installed in accordance with Sections R1003 and R1005, respectively. Flue lining for masonry ...