Mich. Admin. Code R. 408.30547b - [Rescinded effective 8/29/2025] Chimneys

R547b.

Sections R1003.9.1, R1005.4, Figure R1001.1, are amended and Figures R1003.9.1(1) and R1003.9.1(2) are added to read as follows:

R1003.9.1. Chimney caps. Masonry chimneys shall have a concrete, metal, or stone cap sloped a minimum of 10 degrees to shed water, a drip edge or slot and shall be flashed in accordance with figure R1003.9.1(1). The joint space between the flue liner and the cap shall be filled with compressible filler and caulked with a suitable sealant to allow for expansion and contraction of the materials. All vertical joints in a chimney cap shall be caulked with a suitable sealant.

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 C 920, type S or M, grade NS, class 25 and be installed in accordance with the manufacturers installation instructions.

R1005.4. Factory-built chimneys. Chimneys for use with factory-built fireplaces shall comply with the requirements of UL 127. The metal chase cover shall be sloped a minimum of 10^° to shed water. Metal chase cover shall lap down the chimney wall a minimum of 4" (102 mm) and be sealed with a suitable sealant. Exterior wall claddings shall be applied and flashed in accordance with Section R703 and manufacturers installation instructions.

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For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.

Figure R1001.1

Fireplace and Chimney Details

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Notes

Mich. Admin. Code R. 408.30547b

2015 AACS; 2025 MR 10, Eff. 8/29/2025