CBC · California Building Code
Chimneys, fireplaces and masonry heaters
This hub summarizes where to find California Building Code and Residential Code requirements for masonry chimneys, fireplaces and masonry heaters (§2111–§2113; R1001–R1006).
Last reviewed: July 5, 2026
Overview
This topic covers the California code requirements for constructing and installing masonry and factory-built chimneys, fireplaces and masonry heaters — including footing and foundation details, flue sizing and lining, clearances to combustibles, and seismic reinforcing and anchorage. See the residential provisions (Chapter 10, R1001–R1006) for prescriptive requirements that apply to one- and two-family dwellings, and Chapter 21 (masonry) of the California Building Code for the broader masonry and structural rules that apply to buildings regulated by the CBC .
Key CBC sections address masonry fireplaces (§2111), masonry heaters (§2112) and masonry chimneys (§2113); they set requirements for footings, seismic reinforcement, flue linings and termination/clearance for medium- and high‑heat appliances (for example §2111.4 on seismic reinforcing, §2112.2 on compliance/listing for masonry heaters, and §2113.11.3.3 on chimney termination heights) . For factory-built units and venting specifics, consult the residential Chapter 10 listings (R1004–R1006) and the California Mechanical Code references for vent materials and listings .
In this section
Code references
Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:
CRC § 2025 High relevance — show source text
Chapter 6 also regulates exterior windows and doors installed in walls. This chapter contains criteria for the performance of exterior windows and doors and includes provisions for testing and labeling, garage doors, windborne debris protection and anchorage details.
Chapter 7 Wall Covering.
Chapter 7 contains provisions for the design and construction of interior and exterior wall coverings. This chapter establishes the various types of materials, materials standards and methods of application permitted for use as interior coverings, including interior plaster, gypsum board, ceramic tile, wood veneer paneling, hardboard paneling, wood shakes and wood shingles. Chapter 7 also contains requirements for the use of vapor retarders for moisture control in walls.
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Exterior wall coverings provide the weather-resistant exterior envelope that protects the building’s interior from the elements. Chapter 7 provides the requirements for wind resistance and water-resistive barrier for exterior wall coverings. This chapter prescribes the exterior wall coverings as well as the water-resistive barrier required beneath the exterior materials. Exterior wall coverings regulated by this section include aluminum, stone and masonry veneer, wood, hardboard, particleboard, wood structural panel siding, wood shakes and shingles, exterior plaster, steel, vinyl, fiber cement and exterior insulation finish systems.
Chapter 8 Roof-Ceiling Construction.
Chapter 8 regulates the design and construction of roof-ceiling systems. This chapter contains two roof-ceiling framing systems: wood framing and cold-formed steel framing. Allowable span tables are provided to simplify the selection of rafter and ceiling joist size for wood roof framing and cold-formed steel framing. Chapter 8 also provides requirements for the application of ceiling finishes, the proper ventilation of concealed spaces in roofs (e.g., enclosed attics and rafter spaces), unvented attic assemblies and attic access.
Chapter 9 Roof Assemblies.
Chapter 9 regulates the design and construction of roof assemblies. A roof assembly includes the roof deck, vapor retarder, substrate or thermal barrier, insulation, vapor retarder and roof covering. This chapter provides the requirement for wind resistance of roof coverings.
The types of roof covering materials and installation regulated by Chapter 9 are: asphalt shingles, clay and concrete tile, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood shakes and shingles, built-up roofs, metal roof panels, modified bitumen roofing, thermoset and thermoplastic single-ply roofing, sprayed polyurethane foam roofing, liquid applied coatings and photovoltaic shingles. Chapter 9 also provides requirements for roof drainage, flashing, above deck thermal insulation, rooftop-mounted photovoltaic systems and recovering or replacing an existing roof covering.
Chapter 10 Chimneys and Fireplaces.
Chapter 10 contains requirements for the safe construction of masonry chimneys and fireplaces and establishes the standards for the use and installation of factory-built chimneys, fireplaces and masonry heaters. Chimneys and fireplaces constructed of masonry rely on prescriptive requirements for the details of their construction; the factory-built type relies on the listing and labeling method of approval. Chapter 10 provides the requirements for seismic reinforcing and anchorage of masonry fireplaces and chimneys.
Chapter 11 [RE] Energy Efficiency.
Chapter 11 is not adopted in California. See California Energy Code, Title 24, Part 6.
Chapter 12 Mechanical Administration.
CRC § 2025 High relevance — show source text
Chapter 9 Roof Assemblies.
Chapter 9 regulates the design and construction of roof assemblies. A roof assembly includes the roof deck, vapor retarder, substrate or thermal barrier, insulation, vapor retarder and roof covering. This chapter provides the requirement for wind resistance of roof coverings.
The types of roof covering materials and installation regulated by Chapter 9 are: asphalt shingles, clay and concrete tile, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood shakes and shingles, built-up roofs, metal roof panels, modified bitumen roofing, thermoset and thermoplastic single-ply roofing, sprayed polyurethane foam roofing, liquid applied coatings and photovoltaic shingles. Chapter 9 also provides requirements for roof drainage, flashing, above deck thermal insulation, rooftop-mounted photovoltaic systems and recovering or replacing an existing roof covering.
Chapter 10 Chimneys and Fireplaces.
Chapter 10 contains requirements for the safe construction of masonry chimneys and fireplaces and establishes the standards for the use and installation of factory-built chimneys, fireplaces and masonry heaters. Chimneys and fireplaces constructed of masonry rely on prescriptive requirements for the details of their construction; the factory-built type relies on the listing and labeling method of approval. Chapter 10 provides the requirements for seismic reinforcing and anchorage of masonry fireplaces and chimneys.
Chapter 11 [RE] Energy Efficiency.
Chapter 11 is not adopted in California. See California Energy Code, Title 24, Part 6.
Chapter 12 Mechanical Administration.
Chapter 12 is not adopted in California. See California Mechanical Code, Title 24, Part 4.
Chapter 13 General Mechanical System Requirements.
Chapter 13 is not adopted in California. See California Mechanical Code, Title 24, Part 4.
Chapter 14 Heating and Cooling Equipment and Appliances.
Chapter 14 is not adopted in California. See California Mechanical Code, Title 24, Part 4.
Chapter 15 Exhaust Systems.
Chapter 15 is not adopted in California. See California Mechanical Code, Title 24, Part 4.
Chapter 16 Duct Systems.
Chapter 16 is not adopted in California. See California Mechanical Code, Title 24, Part 4.
Chapter 17 Combustion Air.
Chapter 17 is not adopted in California. See California Mechanical Code, Title 24, Part 4.
Chapter 18 Chimneys and Vents.
Chapter 18 is not adopted in California. See California Mechanical Code, Title 24, Part 4.
Chapter 19 Special Appliances, Equipment and Systems.
Chapter 19 is not adopted in California. See California Mechanical Code, Title 24, Part 4.
Chapter 20 Boilers and Water Heaters.
Chapter 20 is not adopted in California. See California Mechanical Code, Title 24, Part 4.
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Chapter 21 Hydronic Piping.
Chapter 21 is not adopted in California. See California Mechanical Code, Title 24, Part 4.
Chapter 22 Special Piping and Storage Systems.
Chapter 22 is not adopted in California. See California Mechanical Code, Title 24, Part 4.
Chapter 23 Solar Thermal Energy Systems.
CBC § 1001.11 High relevance — show source text
3||||X|||||||||||||||||||| |R1001.4||||X|||||||||||||||||||| |Table R1001.1, Footnote (b)||||X|||||||||||||||||||| |R1001.11|||X||||||||||||||||||||| |Figure 1001.11|||X||||||||||||||||||||| |R1001.12|||X||||||||||||||||||||| |R1003.3||||X|||||||||||||||||||| |R1003.4||||X|||||||||||||||||||| |R1003.9.1|||X||||||||||||||||||||| |R1003.9.2|||X||||||||||||||||||||| |R1003.11.3||||X|||||||||||||||||||| |R1003.14||||X|||||||||||||||||||| |R1003.18|||X||||||||||||||||||||| |Figure R1003.18|||X||||||||||||||||||||| |R1003.19|||X||||||||||||||||||||| |R1004.1.1||||X|||||||||||||||||||| |R1004.4||||†||||||||||||||||||||
The state agency does not adopt sections identified with the following symbol: †
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10 CHIMNEYS AND FIREPLACES
User notes:
About this chapter: Chapter 10 contains requirements for the construction, seismic reinforcing and anchorage of masonry chimneys and fireplaces; and establishes standards for the use and installation of factory-built chimneys, fireplaces and masonry heaters. Chimneys and fireplaces constructed of masonry rely on prescriptive requirements for the details of their construction; factory-built versions rely on the listing and labeling method of approval.
SECTION R1001—MASONRY FIREPLACES
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 CHIMNEYS Col2 Col3 ** ITEM** ** LETTERa** ** REQUIREMENTS** Hearth slab thickness A 4 inches Hearth extension (each side of opening) B 8-inch fireplace opening < 6 square feet.
12-inch fireplace opening ≥ 6 square feet.Hearth extension (front of opening) C 16-inch fireplace opening < 6 square feet.
20-inch fireplace opening ≥ 6 square feet.Hearth slab reinforcing D Reinforced to carry its own weight and all imposed loads. Thickness of wall of firebox E 10-inch solid brick or 8 inches where a firebrick lining is used.
Joints in firebrick1/4-inch maximum.Distance from top of opening to throat F 8 inches Smoke chamber wall thickness
Unlined wallsG 6 inches
8 inchesChimney
Vertical reinforcingbH Four No. 4 full-length bars for chimney up to 40 inches wide.
Add two No. 4 bars for each additional 40 inches or fraction of
width or each additional flue.CBC § 2113.11.3.3 High relevance — show source text
2113.11.3.3 Termination height. Concrete and masonry chimneys for high-heat appliances shall extend not less than 20 feet (6096 mm) higher than any portion of any building within 50 feet (15 240 mm).
2113.11.3.4 Clearance. Concrete and masonry chimneys for high-heat appliances shall have approved clearance from buildings and structures to prevent overheating combustible materials, permit inspection and maintenance operations on the chimney and prevent danger of burns to persons.
2113.12 Clay flue lining (installation). Clay flue liners shall be installed in accordance with ASTM C1283 and extend from a point not less than 8 inches (203 mm) below the lowest inlet or, in the case of fireplaces, from the top of the smoke chamber to a point above the enclosing walls. The lining shall be carried up vertically, with a maximum slope not greater than 30 degrees (0.52 rad) from the vertical.
Clay flue liners shall be laid in medium-duty nonwater-soluble 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 lining shall be supported on all sides. Only enough mortar shall be placed to make the joint and hold the liners in position.
2113.13 Additional requirements.
2113.13.1 Listed materials. Listed materials used as flue linings shall be installed in accordance with the terms of their listings and the manufacturer’s instructions.
2113.13.2 Space around lining. The space surrounding a chimney lining system or vent installed within a masonry chimney shall not be used to vent any other appliance.
Exception: This shall not prevent the installation of a separate flue lining in accordance with the manufacturer’s instructions.
2113.14 Multiple flues. Where two or more flues are located in the same chimney, masonry wythes shall be built between adjacent flue linings. The masonry wythes shall be not less than 4 inches (102 mm) thick and bonded into the walls of the chimney.
Exception: Where venting only one appliance, two flues are 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).
2113.15 Flue area (appliance). Chimney flues shall not be smaller in area than the area of the connector from the appliance. 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.
Exceptions:
- Chimney flues serving oil-fired appliances sized in accordance with NFPA 31.
- Chimney flues serving gas-fired appliances sized in accordance with the California Mechanical Code .
2113.16 Flue area (masonry fireplace). Flue sizing for chimneys serving fireplaces shall be in accordance with Section 2113.16.1 or 2113.16.2.
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FIGURE 2113.16—FLUE SIZES FOR MASONRY CHIMNEYS
CBC § 404.6 High relevance — show source text
Exceptions:
- Glass-block assemblies having a fire protection rating of not less than [3] / 4 hour shall be permitted as opening protectives in accordance with Section 716 in fire barriers, fire partitions and smoke barriers that have a required fireresistance rating of 1 hour or less and do not enclose exit stairways and ramps or exit passageways.
- Glass-block assemblies as permitted in Section 404.6, Exception 2.
SECTION 2111 A —MASONRY FIREPLACES
2111 A .1 General. The construction of masonry fireplaces, consisting of concrete or masonry, shall be in accordance with this section.
2111 A .2 Fireplace drawings. The construction documents shall describe in sufficient detail the location, size and construction of masonry fireplaces. The thickness and characteristics of materials and the clearances from walls, partitions and ceilings shall be indicated.
2111 A .3 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 (153 mm) beyond the face of the fireplace or
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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.
2111 A .3.1 Ash dump cleanout. Cleanout openings, located within foundation walls below fireboxes, where provided, shall be equipped with ferrous metal or masonry doors and frames constructed to remain tightly closed, except when in use. Cleanouts shall be accessible and located so that ash removal will not create a hazard to combustible materials.
2111 A .4 Seismic reinforcement. In structures assigned to Seismic Design Category A or B, seismic reinforcement is not required. In structures assigned to Seismic Design Category C or D, masonry fireplaces shall be reinforced and anchored in accordance with Sections 2111 A .4.1, 2111 A .4.2 and 2111 A .5. In structures assigned to Seismic Design Category E or F, masonry fireplaces shall be reinforced in accordance with the requirements of Sections 2101 A through 2108 A .
2111 A .4.1 Vertical reinforcing. For fireplaces with chimneys up to 40 inches (1016 mm) wide, four No. 4 continuous vertical bars, anchored in the foundation, shall be placed in the concrete between wythes of solid masonry or within the cells of hollow unit masonry and grouted in accordance with Section 2103.3. For fireplaces with chimneys greater than 40 inches (1016 mm) wide, two additional No. 4 vertical bars shall be provided for each additional 40 inches (1016 mm) in width or fraction thereof. 2111 A **.4.2 Horizontal reinforcing.
CBC § 9-4 High relevance — show source text
R904 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4
R905 Requirements for Roof Coverings . . . . . . . . . . . . . . . . 9-4
R906 Roof Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-19
R907 Rooftop-Mounted Photovoltaic Panel Systems . . . 9-19
R908 Reroofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-19
R909 Roof Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-20
CHAPTER 10 CHIMNEYS AND FIREPLACES . . . . . . . . . . . .10-3
R1001 Masonry Fireplaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3
R1002 Masonry Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-6
R1003 Masonry Chimneys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7
R1004 Factory-Built Fireplaces. . . . . . . . . . . . . . . . . . . . . . . . 10-12
R1005 Factory-Built Chimneys . . . . . . . . . . . . . . . . . . . . . . . . 10-12
R1006 Exterior Air Supply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-12
Part IV—Energy Conservation. . . . . . . . . . . . . . . . . . . . . . . .11-1
Part V—Mechanical. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-1
Part VI—Fuel Gas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24-1
Part VII—Plumbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25-1
Part VIII—Electrical. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34-1
Part IX— Referenced Standards . . . . . . . . . . . . . . . . . . . . . .44-3
CHAPTER 44 REFERENCED STANDARDS . . . . . . . . . . . . . .44-3
CBC § 21-5 High relevance — show source text
2104 Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-5
2105 Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-6
2106 Seismic Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-7
2107 Allowable Stress Design. . . . . . . . . . . . . . . . . . . . . . . . 21-8
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CONTENTS
2108 Strength Design of Masonry . . . . . . . . . . . . . . . . . . . . 21-8
2109 Empirical Design of Adobe Masonry . . . . . . . . . . . . . 21-9
2110 Glass Unit Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-11
2111 Masonry Fireplaces . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-11
2112 Masonry Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-13
2113 Masonry Chimneys . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-14
2114 Dry-Stack Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-19
2115 Additional Requirements for Community Colleges
[DSA-SS/CC]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-19
CHAPTER 21A MASONRY . . . . . . . . . . . . . . . . . . . . . . . . . . .21A-1
2101A General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-3
2102A Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-4
2103A Masonry Construction Materials. . . . . . . . . . . . . . . . . . 21A-4
2104A Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-5
2105A Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-7
CBC § 2112.1 High relevance — show source text
SECTION 2112—MASONRY HEATERS
2112.1 Definition. A masonry heater is a heating appliance constructed of concrete or solid masonry, hereinafter referred to as “masonry,” which is designed to absorb and store heat from a solid fuel fire built in the firebox by routing the exhaust gases through internal heat exchange channels in which the flow path downstream of the firebox includes flow in either a horizontal or downward direction before entering the chimney and which delivers heat by radiation from the masonry surface of the heater.
2112.2 Installation. Masonry heaters shall be installed in accordance with this section and comply with one of the following:
- Masonry heaters shall comply with the requirements of ASTM E1602.
- Masonry heaters shall be listed and labeled in accordance with UL 1482 or EN 15250 and installed in accordance with the manufacturer’s instructions.
2112.3 Footings and foundation. The firebox floor of a masonry heater shall be a minimum thickness of 4 inches (102 mm) of noncombustible material and be supported on a noncombustible footing and foundation in accordance with Section 2113.2.
2112.4 Seismic reinforcing. In structures assigned to Seismic Design Category D, E or F, masonry heaters shall be anchored to the masonry foundation in accordance with Section 2113.3. Seismic reinforcing shall not be required within the body of a masonry heater with a height that is equal to or less than 3.5 times its body width and where the masonry chimney serving the heater is not
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supported by the body of the heater. Where the masonry chimney shares a common wall with the facing of the masonry heater, the chimney portion of the structure shall be reinforced in accordance with Section 2113.
2112.5 Masonry heater clearance. Combustible materials shall not be placed within 36 inches (914 mm) or the distance of the allowed reduction method from the outside surface of a masonry heater in accordance with NFPA 211, Section 12.6, and the required space between the heater and combustible material shall be fully vented to permit the free flow of air around all heater surfaces.
Exceptions:
- Where the masonry heater wall thickness is not less than 8 inches (203 mm) of solid masonry and the wall thickness of the heat exchange channels is not less than 5 inches (127 mm) 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 EN 15250 and installed in accordance with the manufacturer’s instructions.
SECTION 2113—MASONRY CHIMNEYS
2113.1 General. The construction of masonry chimneys consisting of solid masonry units, hollow masonry units grouted solid, stone or concrete shall be in accordance with this section.
CBC § 1.1 Medium relevance — show source text
1.1_|||||||||X||X|X|||X|||||||||| |2101.1.2|||||||||X||X|X|||X|||||||||| |2101.1.3|||||||||X||X|X|||X|||||||||| |2101.1.4|||||||||X|||||||||||||||| |2101.1.5|||||||||X|||||||||||||||| |2101.2|||||||||||X|X|||X|||||||||| |2101.2.2|||||||||||X|X|||X|||||||||| |2103.1|||||||||||X|X|||X|||||||||| |2103.4|||||||||||X|X|||X|||||||||| |2103.5|||||||||||X|X|||X|||||||||| |2103.6|||||||||||X|X|||X|||||||||| |2104.2|||||||||||X|X|||X|||||||||| |2104.3|||||||||||X|X|||X|||||||||| |2105.2|||||||||||X|X|||X|||||||||| |2105.3|||||||||||X|X|||X|||||||||| |2105.4|||||||||||X|X|||X|||||||||| |2106.1.1|||||||||||X|X|||X|||||||||| |2106.1.2|||||||||||X|X|||X|||||||||| |2106.1.3|||||||||||X|X|||X|||||||||| |2107.1|||||||||||X|X|||X|||||||||| |2107.5|||||||||||X|X|||X|||||||||| |2109|||||||||||X|X|||X|||||||||| |2109.2.4.8.2|||||||||||||||||||||X|||| |2110.1|||||||||||X|X|||X|||||||||| |2113.9.2|||X|||||||||||||||||||||| |2115|||||||||X||||||||||||||||
The state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.
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21 MASONRY
User notes:
About this chapter: Chapter 21 establishes minimum requirements for masonry construction. The provisions address: material specifications and test methods; types of wall construction; criteria for engineered and empirical designs; and required details of construction, including the execution of construction. The provisions provide a framework for applying applicable standards to the design and construction of masonry structures. Masonry design methodologies including allowable stress design, strength design and empirical design are covered by the provisions of this chapter. Also addressed are masonry fireplaces and chimneys, masonry heaters and glass unit masonry.
ICC code development note: Code change proposals to this chapter will be considered by the IBC—Structural Code Development Committee during the
2025 (Group B) Code Development Cycle.
CBC § 25.4 Medium relevance — show source text
Not required in Seismic Design Category A or B.|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 require-
ments 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 or B.|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 require-
ments 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 or B.|2025 CALIFORNIA RESIDENTIAL CODE 10-3
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CHIMNEYS AND FIREPLACES
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
FIGURE R1001.1—FIREPLACE AND CHIMNEY DETAILS
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 provided, shall be equipped with ferrous metal or masonry doors and frames constructed to remain tightly closed except when in use. Cleanouts shall be located to allow access so that ash removal will not create a hazard to combustible materials.
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
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on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
CHIMNEYS AND FIREPLACES
CBC § 12.4.5.2 Medium relevance — show source text
(2) The vent system shall be installed such that no fittings or joints between sections are installed in the above-ceiling space.
(3) The venting system shall be installed in a conduit or enclosure with joints between the interior of the enclosure and the ceiling space sealed. [NFPA 54:12.4.5.2] 802.4 Type of Venting System to be Used. The type of venting system to be used shall be in accordance with Table 802.4. [NFPA 54:12.5.1]
802.4.1 Plastic Piping. Where plastic piping is used to vent an appliance, the appliance shall be listed for use with such venting materials and the appliance manufacturer’s installation instructions shall identify the specific plastic piping material. The plastic pipe venting materials shall be labeled in accordance with the product standards specified by the appliance manufacturer or shall be listed and labeled in accordance with UL 1738. [NFPA 54:12.5.2]
802.4.2 Plastic Vent Joints. Plastic pipe and fittings used to vent appliances shall be installed in accordance with the appliance manufacturer’s installation instructions. Plastic pipe venting materials listed and labeled in accordance with UL 1738 shall be installed in accordance
with the vent manufacturer’s installation instructions. Where primer is required, it shall be of a contrasting color.
[NFPA 54:12.5.3]
802.4.3 Special Gas Vents. Special gas vents shall be listed and labeled in accordance with UL 1738 and installed in accordance with the special gas vent manufacturer’s installation instructions. [NFPA 54:12.5.4]
802.5 Masonry, Metal, and Factory-Built Chimneys. Chimneys shall be installed in accordance with Section 802.5.1 through Section 802.5.3.
802.5.1 Factory-Built Chimneys. Factory-built chimneys shall be listed in accordance with UL 103, UL 959, or UL 2561. Factory-built chimneys used to vent appliances that operate at positive vent pressure shall be listed for such application. [NFPA 54:12.6.1.1]
802.5.1.1 Decorative Shrouds. Decorative shrouds addressed in Section 802.5.4.3 shall comply with UL 103 for factory-built residential chimneys, UL 127 for factory-built fireplaces, or UL 1482 for solid-fuel room heaters.
802.5.2 Metal Chimneys. Metal chimneys shall be built and installed in accordance with NFPA 211. [NFPA 54:12.6.1.2]
802.5.3 Masonry Chimneys. Masonry chimneys shall be built and installed in accordance with NFPA 211 and lined with one of the following:
(1) Approved clay flue lining.
(2) A chimney lining system listed and labeled in accordance with UL 1777.
(3) Other approved material that resists corrosion, erosion, softening, or cracking from vent gases at temperatures up to 1800°F (982°C).
Exception: Masonry chimney flues lined with a chimney lining system specifically listed for use with listed appliances with draft hoods, Category I appliances, and
154 2025 CALIFORNIA MECHANICAL CODE
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CHIMNEYS AND VENTS
CBC § 21A-8 Medium relevance — show source text
2106A Seismic Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-8
2107A Allowable Stress Design . . . . . . . . . . . . . . . . . . . . . . . . . 21A-9
2108A Strength Design of Masonry. . . . . . . . . . . . . . . . . . . . . 21A-10
2109A Empirical Design of Adobe Masonry . . . . . . . . . . . . . 21A-10
2110A Glass Unit Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-10
2111A Masonry Fireplaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-10
2112A Masonry Heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-13
2113A Masonry Chimneys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-13
2114A Dry-Stack Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21A-18
CHAPTER 22 STEEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-1
2201 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-3
2202 Structural Steel and Composite Structural Steel and Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . 22-4
2203 Structural Stainless Steel . . . . . . . . . . . . . . . . . . . . . . 22-6
2204 Cold-Formed Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-6
2205 Cold-Formed Stainless Steel. . . . . . . . . . . . . . . . . . . . 22-6
2206 Cold-Formed Steel Light-Frame Construction . . . . 22-6
2207 Steel Joists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-7
2208 Steel Deck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-8
2209 Steel Storage Racks . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-8
Frequently asked questions
Do masonry heaters need to be tested or listed to a standard?
Yes. Masonry heaters must either comply with ASTM E1602 or be listed and labeled (for example to UL 1482 or EN 15250) and installed per the manufacturer's instructions, as required by §2112.2 .
Where are the seismic reinforcement requirements for fireplaces and chimneys?
Seismic reinforcing requirements for masonry fireplaces are in §2111.4 of the CBC and residential seismic rules are summarized in R1001.3 for the CRC; chimneys also have specific reinforcement and anchorage provisions in §2113 and related masonry provisions in Chapter 21 .
Can I use a factory-built fireplace or chimney instead of masonry?
Yes. Factory-built fireplaces and chimneys are permitted when listed and installed in accordance with their listing and manufacturer’s instructions; see R1004–R1005 in the Residential Code and the Mechanical Code for venting and listing requirements .
More in California Building Code
- Administration & Permits
- Energy Efficiency
- Existing Buildings
- Occupancy Classification & Use
- Hazardous Materials & Occupancies
- Types of Construction
- Fire-Resistance & Fire Safety
- Interior Finishes
- Means of Egress
- Accessibility
- Exterior Walls
- Roofing & Roof Assemblies
- Structural Design
- Special Inspections & Tests
- Foundations & Soils
- Concrete
- Masonry
- Steel
- Wood
- Elevators & Conveying Systems
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