Section R1001 — MASONRY FIREPLACES — 2025 California Residential Code (Title 24, Part 2.5)

R1001.1 General. ¶

R1001.1 General. Masonry fireplaces shall be constructed in accordance with this section and the applicable provisions of Chapters 3 and 4. TABLE R1001.1—SUMMARY OF REQUIREMENTS FOR MASONRY FIREPLACES AND CHIMNEYSCol2Col3 --------- ITEM LETTERa REQUIREMENTS Hearth slab thicknessA4 inches Hearth extension (each side of opening)B8-inch fireplace opening < 6 square feet.<br12-inch fireplace opening ≥ 6 square feet. Hearth extension (front of opening)C16-inch fireplace opening < 6 square feet.<br20-inch fireplace opening ≥ 6 square feet. Hearth slab reinforcingDReinforced to carry its own weight…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use

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R1001.2 Footings and foundations. ¶

R1001.2 Footings and foundations. Footings for masonry fireplaces and their chimneys shall be constructed of concrete or solid masonry not less than 12 inches (305 mm) thick and shall extend not less than 6 inches (152 mm) beyond the face of the fireplace or foundation wall on all sides. Footings shall be founded on natural, undisturbed earth or engineered fill below frost depth. In areas not subjected to freezing, footings shall be not less than 12 inches (305 mm) below finished grade. R1001.2.1 Ash dump cleanout. Cleanout openings located within foundation walls below fireboxes, where…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application

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R1001.3 Seismic reinforcing. ¶

R1001.3 Seismic reinforcing. Masonry or concrete chimneys in all structures regulated by this code assigned to Seismic Design Category C, D 0, D 1 or D 2 shall be reinforced. Reinforcing shall conform to the requirements set forth in Table R1001.1 and Section R606. R1001.3.1 Vertical reinforcing. For chimneys up to 40 inches (1016 mm) wide, four No. 4 continuous vertical bars shall be placed between wythes of solid masonry or within the cells of hollow unit masonry and grouted in accordance with Section R606. Grout 10-4 2025 CALIFORNIA RESIDENTIAL CODE on Jul 18, 2025 11:14 AM (CDT)…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use

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R1001.4 Seismic anchorage. ¶

R1001.4 Seismic anchorage. Masonry or concrete chimneys in all structures regulated by this code assigned to Seismic Design Category C, D 0, D 1 or D 2 shall be anchored at each floor, ceiling or roof line more than 6 feet (1829 mm) above grade, except where constructed completely within the exterior walls. Anchorage shall conform to the requirements of Section R1001.4.1. R1001.4.1 Anchorage. Two [3] / 16 -inch by 1-inch (5 mm by 25 mm) straps shall be embedded not less than 12 inches (305 mm) into the chimney. Straps shall be hooked around the outer bars and extend 6 inches (152 mm) beyond…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use

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R1001.5 Firebox walls. ¶

R1001.5 Firebox walls. Masonry fireboxes shall be constructed of solid masonry units, hollow masonry units grouted solid, stone or concrete. Where a lining of firebrick not less than 2 inches (51 mm) thick or other approved lining is provided, the minimum thickness of back and sidewalls shall each be 8 inches (203 mm) of solid masonry, including the lining. The width of joints between firebricks shall not be greater than [1] / 4 inch (6.4 mm). Where a lining is not provided, the total minimum thickness of back and side walls shall be 10 inches (254 mm) of solid masonry. Firebrick shall…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use

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R1001.6 Firebox dimensions. ¶

R1001.6 Firebox dimensions. The firebox of a concrete or masonry fireplace shall have a depth of not less than 20 inches (508 mm). The throat shall be not less than 8 inches (203 mm) above the fireplace opening. The throat opening shall be not less than 4 inches (102 mm) deep. The cross-sectional area of the passageway above the firebox, including the throat, damper and smoke chamber, shall be not less than the cross-sectional area of the flue. 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…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking

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R1001.7 Lintel and throat. ¶

R1001.7 Lintel and throat. Masonry over a fireplace opening shall be supported by a lintel of noncombustible material. The minimum required bearing length on each end of the fireplace opening shall be 4 inches (102 mm). The fireplace throat or damper shall be located not less than 8 inches (203 mm) above the lintel. R1001.7.1 Damper. Masonry fireplaces shall be equipped with a ferrous metal damper located not less than 8 inches (203 mm) above the top of the fireplace opening. Dampers shall be installed in the fireplace or the chimney venting the fireplace, and shall be operable from the room…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback

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R1001.8 Smoke chamber. ¶

R1001.8 Smoke chamber. Smoke chamber walls shall be constructed of solid masonry units, hollow masonry units grouted solid, stone or concrete. The total minimum thickness of front, back and side walls shall be 8 inches (203 mm) of solid masonry. The inside surface shall be parged smooth with refractory mortar conforming to ASTM C199. Where a lining of firebrick not less than 2 inches (51 mm) thick, or a lining of vitrified clay not less than [5] / 8 inch (16 mm) thick, is provided, the total minimum thickness of front, back and side walls shall be 6 inches (152 mm) of solid masonry, including…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use

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R1001.9 Hearth and hearth extension. ¶

R1001.9 Hearth and hearth extension. Masonry fireplace hearths and hearth extensions shall be constructed of concrete or masonry, supported by noncombustible materials, and reinforced to carry their own weight and all imposed loads. Combustible material shall not remain against the underside of hearths and hearth extensions after construction. R1001.9.1 Hearth thickness. The minimum thickness of fireplace hearths shall be 4 inches (102 mm). R1001.9.2 Hearth extension thickness. The minimum thickness of hearth extensions shall be 2 inches (51 mm). Exception: Where the bottom of the firebox…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard

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R1001.10 Hearth extension dimensions. ¶

R1001.10 Hearth extension dimensions. Hearth extensions shall extend not less than 16 inches (406 mm) in front of and not less than 8 inches (203 mm) beyond each side of the fireplace opening. Where the fireplace opening is 6 square feet (0.6 m [2] ) or larger, the hearth extension shall extend not less than 20 inches (508 mm) in front of and not less than 12 inches (305 mm) beyond each side of the fireplace opening.

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review

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R1001.11 Fireplace clearance. ¶

R1001.11 Fireplace clearance. Wood beams, joists, studs and other combustible material shall have a clearance of not less than 2 inches (51 mm) from the front faces and sides of masonry fireplaces and not less than 4 inches (102 mm) from the back faces of masonry fireplaces. The airspace shall not be filled, except for noncombustible material or to provide fireblocking in accordance with Section R1001.12. Exceptions: 1. 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…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use

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