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Chapter 5 — GENERAL BUILDING HEIGHTS AND AREAS

Section 508 — MIXED USE AND OCCUPANCY

2025 California Building Code (Title 24, Part 2) · 2025 edition · updated 2026-07-29 · California

Italicized text is a California amendment to the model code, as printed in the official publication.

508.1 General.

Each portion of a building shall be individually classified in accordance with Section 302.1. Where a building contains more than one occupancy group, the building or portion thereof shall comply with the applicable provisions of Section 508.2, 508.3, 508.4 or 508.5, or a combination of these sections.

Exceptions:

  1. Occupancies separated in accordance with Section 510.
  2. Where required by Table 415.6.5, areas of Group H-1, H-2 and H-3 occupancies shall be located in a detached building or structure.

508.2 Accessory occupancies.

Accessory occupancies are those occupancies that are ancillary to the main occupancy of the building or portion thereof. Accessory occupancies shall comply with the provisions of Sections 508.2.1 through 508.2.4.

508.2.1 Occupancy classification. Accessory occupancies shall be individually classified in accordance with Section 302.1. The requirements of this code shall apply to each portion of the building based on the occupancy classification of that space.

508.2.2 Allowable building height. The allowable height and number of stories of the building containing accessory occupancies shall be in accordance with Section 504 for the main occupancy of the building.

508.2.3 Allowable building area. The allowable area of the building shall be based on the applicable provisions of Section 506 for the main occupancy of the building. Aggregate accessory occupancies shall not occupy more than 10 percent of the floor area of the story in which they are located and shall not exceed the tabular values for nonsprinklered buildings in Table 506.2 for each such accessory occupancy.

508.2.4 Separation of occupancies. No separation is required between accessory occupancies and the main occupancy.

Exceptions:

  1. Group H-2, H-3, H-4 and H-5 and L occupancies shall be separated from all other occupancies in accordance with Section 508.4.

  2. Group R-1, R-2, R-2.1, R-2.2 and R-3 dwelling units and sleeping units shall be separated from other dwelling or sleeping units and from accessory occupancies contiguous to them in accordance with the requirements of Section 420. 3. Group I-2 shall be separated from all other occupancies in accordance with Section 508.4. Exception: No separation is required between Group B, E and R-1 sleeping units accessory to Group I-2 and covered exte- rior entrances required by Section 11B-206.4.10 or Section 1224.33.2.1 accessory to Group I-2. 4. Group I-3 shall be separated from all other occupancies in accordance with Section 508.4.

508.3 Nonseparated occupancies.

Buildings or portions of buildings that comply with the provisions of this section shall be considered as nonseparated occupancies.

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

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GENERAL BUILDING HEIGHTS AND AREAS

508.3.1 Occupancy classification. Nonseparated occupancies shall be individually classified in accordance with Section 302.1. The requirements of this code shall apply to each portion of the building based on the occupancy classification of that space. In addition, the most restrictive provisions of Chapter 9 that apply to the nonseparated occupancies shall apply to the total nonseparated occupancy area.

508.3.1.1 High-rise buildings. Where nonseparated occupancies occur in a high-rise building, the most restrictive requirements of Section 403 that apply to the nonseparated occupancies shall apply throughout the high-rise building.

508.3.1.2 Group I-2, Condition 2 occupancies. Where one of the nonseparated occupancies is Group I-2, Condition 2, the most restrictive requirements of Sections 407, 509 and 712 shall apply throughout the fire area containing the Group I-2 occupancy. The most restrictive requirements of Chapter 10 shall apply to the path of egress from the Group I-2, Condition 2 occupancy up to and including the exit discharge.

508.3.2 Allowable building area, height and number of stories. The allowable building area, height and number of stories of the building or portion thereof shall be based on the most restrictive allowances for the occupancy groups under consideration for the type of construction of the building in accordance with Section 503.1.

508.3.3 Separation. No separation is required between nonseparated occupancies.

Exceptions:

  1. Group H-2, H-3, H-4 and H-5 , I-2 and L occupancies shall be separated from all other occupancies in accordance with Section 508.4.

  2. Group R-1, R-2, R-2.1, R-2.2 and R-3 dwelling units and sleeping units shall be separated from other dwelling or sleeping units and from other occupancies contiguous to them in accordance with the requirements of Section 420. 3. Where Group I-3 is not the main occupancy and the area is greater than 10 percent of the floor area, it shall be separated per Table 508.4.

508.4 Separated occupancies.

Buildings or portions of buildings that comply with the provisions of this section shall be considered as separated occupancies.

TABLE 508.4—REQUIRED SEPARATION OF OCCUPANCIES (HOURS)f

OCCUPANCY A, E A, E I-4_i, _
R-2.1		 I-4_i, _
R-2.1		 I-2j I-2j I-3 I-3 R_-1a, R-2a, _
_R-2.2a, R-3a, _
R-3.1a, R-4a		 R_-1a, R-2a, _
_R-2.2a, R-3a, _
R-3.1a, R-4a		 F-2,
S-2b, U		 F-2,
S-2b, U		 Be, F-1**g, h, **
M,S-1		 Be, F-1**g, h, **
M,S-1		 L L H-1 H-1 H-2 H-2 H-3, H-4 H-3, H-4 H-5 H-5
OCCUPANCY S NS S NS S NS S NS S NS S NS S NS S NS S NS S NS S NS S NS
A, E N N 1 2 2 NP 2 NP 1 2 N 1 1 2 2 NP NP NP 3 4 2 3 2 NP
I-4_i, R-2.1_ 1 2 N N 2 NP 2 NP 1 NP 1 2 1 2 2 NP NP NP 4 NP 2 NP 4 NP
I-2_j_ 2 NP 2 NP N N 2 NP 2 NP 2 NP 2 NP 2 NP NP NP 4 NP 2 NP 4 NP
I-3 2 NP 2 NP 2 NP N NP 2 NP 2 2 2 2 2 NP NP NP 4 NP 4 NP 4 NP
R_-1_a, R-2a,
_R-2.2a, R-3a, _
_R-3.1a, R-4a _		 1 2 1 NP 2 NP 2 NP N N 1c 2c 1 2 4 NP NP NP 3 NP 2 NP 2 NP
F-2, S-2b, U N 1 1 2 2 NP 2 2 1c 2c N N 1 2 1 NP NP NP 3 4 2 3 2 NP
Be, F-1_g, h_, M,
S-1		 1 2 1 2 2 NP 2 2 1 2 1 2 N N 1 NP NP NP 2 3 1 2 1 NP
L 2 NP 2 NP 2 NP 2 NP 4 NP 1 NP 1 NP 1 NP NP NP 2 NP 1 NP 1 NP
H-1 NP NP NP NP NP NP NP NP NP NP NP NP NP NP NP NP N NP NP NP NP NP NP NP
H-2 3 4 4 NP 4 NP 4 NP 3 4 3 4 2 3 2 NP NP NP N NP 1 NP 1 NP
H-3, H-4 2 3 4 NP 4 NP 4 NP 2 3 2 3 1 2 1 NP NP NP 1 NP 1d NP 1 NP
H-5 2 NP 4 NP 4 NP 4 NP 2 NP 2 NP 1 NP 1 NP NP NP 1 NP 1 NP N NP

S = Buildings equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.1.
NS = Buildings not equipped throughout with an automatic sprinkler system installed in accordance with Section 903.3.1.1.
N = No separation requirement.
NP = Not Permitted.
a. See Section 420.
b. The required separation from areas used only for private or pleasure vehicles shall be reduced by 1 hour but not to less than 1 hour.
c. See Sections 406.3.2 and 406.6.4.
d. Separation is not required between occupancies of the same classification.
e. See Section 422.2 for ambulatory care facilities.
f. Occupancy separations that serve to define fire area limits established in Chapter 9 for requiring fire protection systems shall also comply with Section 707.3.10 and Table
707.3.10 in accordance with Section 901.7.
g._ [SFM]_Group I and F1 occupancies and Group R-2.1 and F-1 occupancies shall have a 3 hour separation.
h._ [SFM]_Commercial kitchens not associated with cafeterias and similar dining facilities in Group I-2 and Group R-2.1 shall have a 2-hour separation and shall be protected by an
automatic sprinkler system.
i._ [SFM]__ Group E child-care separation with I-4 child care can be reduced to 1 hour with the installation of automatic fire sprinklers in accordance with Section 903.3.1.1.
 j. When not considered an accessory use in accordance with Section 508.2.4, the required separation between Group I-2 and required covers for accessible entrances and emergency_
vehicle entrances, when in accordance with Section 406.5.2 and protected by an automatic sprinkler system, shall be reduced by 1 hour but not to less than 1 hour. See Section
903.2.21.

5-16 2025 CALIFORNIA BUILDING CODE

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

GENERAL BUILDING HEIGHTS AND AREAS

508.4.1 Occupancy classification. Separated occupancies shall be individually classified in accordance with Section 302.1. Each separated space shall comply with this code based on the occupancy classification of that portion of the building. The most restrictive provisions of Chapter 9 that apply to the separate occupancies shall apply to the total nonfire-barrier-separated occupancy areas. Occupancy separations that serve to define fire area limits established in Chapter 9 for requiring a fire protection system shall also comply with Section 901.7.

508.4.2 Allowable building area. In each story, the building area shall be such that the sum of the ratios of the actual building area of each separated occupancy divided by the allowable building area of each separated occupancy shall not exceed 1.

508.4.3 Allowable building height and number of stories. Each separated occupancy shall comply with the building height limitations and story limitations based on the type of construction of the building in accordance with Section 503.1.

Exception: Special provisions of Section 510 shall permit occupancies at building heights and number of stories other than provided in Section 503.1.

508.4.4 Separation. Individual occupancies shall be separated from adjacent occupancies in accordance with Table 508.4.

508.4.4.1 Construction. Required separations shall be fire barriers constructed in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 711, or both, so as to completely separate adjacent occupancies. Mass timber elements serving as fire barriers or horizontal assemblies to separate occupancies in Type IV-B or IV-C construction shall be separated from the interior of the building with an approved thermal barrier consisting of gypsum board that is not less than [1] / 2 inch (12.7 mm) in thickness or a material that is tested in accordance with and meets the acceptance criteria of both the Temperature Transmission Fire Test and the Integrity Fire Test of NFPA 275.

Exception: A thermal barrier shall not be required on the top of horizontal assemblies serving as occupancy separations.

508.5 Live/work units. Live/work units shall comply with one of the following:

  1. For a live/work unit located in a building constructed in accordance with this code, both the residential and nonresidential portions of the live/work unit shall comply with Sections 508.5 through 508.5.11.
  2. For a live/work unit located in a building constructed in accordance with the California Residential Code, the nonresidential portion of the live/work unit shall comply with Sections 508.5.1 through 508.5.11, and the residential portion of the live/work unit shall be constructed in accordance with the California Residential Code and Section 508.5.7.

Exception s : 1. Dwelling or sleeping units that include an office that is less than 10 percent of the area of the dwelling unit are permitted to be classified as dwelling units with accessory occupancies in accordance with Section 508.2. 2. Live/work units complying with the requirements of Section 508.5 shall be permitted to be constructed as one- and two- family dwellings or townhouses in accordance with the California Residential Code, as applicable.

508.5.1 Limitations. The following shall apply to live/work areas:

  1. The live/work unit is permitted to be not greater than 3,000 square feet (279 m [2] ) in area.
  2. The nonresidential area is permitted to be not more than 50 percent of the area of each live/work unit.
  3. The nonresidential area function shall be limited to the first or main floor only of the live/work unit.

508.5.2 Occupancies. Live/work units shall be classified as a Group R-2 occupancy. Separation requirements found in Sections 420 and 508 shall not apply within the live/work unit where the live/work unit is in compliance with Section 508.5. Nonresidential uses that would otherwise be classified as either a Group H or S occupancy shall not be permitted in a live/work unit.

Exception: Storage shall be permitted in the live/work unit provided that the aggregate area of storage in the nonresidential portion of the live/work unit shall be limited to 10 percent of the space dedicated to nonresidential activities.

[BE] 508.5.3 Means of egress. Except as modified by this section, the means of egress components for a live/work unit shall be designed in accordance with Chapter 10 for the function served.

Exception: Residential areas of live/work units constructed in accordance with the California Residential Code shall not be required to comply with Chapter 10.

[BE] 508.5.4 Egress capacity. The egress capacity for each element of the live/work unit shall be based on the occupant load for the function served in accordance with Table 1004.5.

[BE] 508.5.5 Spiral stairways. Spiral stairways that conform to the requirements of Section 1011.10 shall be permitted.

[BE] 508.5.6 Vertical openings. Floor openings between floor levels of a live/work unit are permitted without enclosure.

[F] 508.5.7 Fire protection. Live/work units in buildings constructed in accordance with this code shall be provided with all of the following:

  1. An automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2.

  2. Smoke alarms in accordance with Section 907.2.11.

  3. Where required by Section 907.2.9.2, a manual fire alarm system.

Live/work units in buildings constructed in accordance with the California Residential Code shall be provided with an automatic sprinkler system and smoke alarms. The automatic sprinkler system shall comply with California Residential Code Section R309, and smoke alarms shall comply with California Residential Code Section 310.

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GENERAL BUILDING HEIGHTS AND AREAS

508.5.8 Structural. Floors within a live/work unit shall be designed for the live loads in Table 1607.1, based on the function within the space.

Exception: Residential areas of live/work units constructed in accordance with the California Residential Code shall not be required to comply with Table 1607.1.

[BE] 508.5.9 Accessibility. Accessibility shall be designed in accordance with Chapter 11A and/or 11B, when applicable, for the function served.

508.5.10 Ventilation. The applicable ventilation requirements of the California Mechanical Code shall apply to each area within the live/work unit for the function within that space.

508.5.11 Plumbing facilities. The nonresidential area of the live/work unit shall be provided with minimum plumbing facilities as specified by the California Plumbing Code, based on the function of the nonresidential area. Where the nonresidential area of the live/work unit is required to be accessible, the plumbing fixtures specified by the California Plumbing Code shall be accessible.

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▸ Contents — 2025 California Building Code (Title 24, Part 2)
2025 California Building Code (Title 24, Part 2)
  1. Chapter 1 — ADMINISTRATION
  2. Chapter 2 — DEFINITIONS
  3. Chapter 3 — OCCUPANCY CLASSIFICATION AND USE
  4. Chapter 4 — SPECIAL DETAILED REQUIREMENTS BASED ON OCCUPANCY A…
  5. ▸ Chapter 5 — GENERAL BUILDING HEIGHTS AND AREAS
    Overview
    1. Section 501 — GENERAL
    2. Section 502 — BUILDING ADDRESS
    3. Section 503 — GENERAL BUILDING HEIGHT AND AREA LIMITATIONS
    4. Section 504 — BUILDING HEIGHT AND NUMBER OF STORIES
    5. Section 505 — MEZZANINES AND EQUIPMENT PLATFORMS
    6. Section 506 — BUILDING AREA
    7. Section 507 — UNLIMITED AREA BUILDINGS
    8. Section 508 — MIXED USE AND OCCUPANCY
    9. Section 509 — INCIDENTAL USES
    10. Section 510 — SPECIAL PROVISIONS
  6. Chapter 6 — TYPES OF CONSTRUCTION
  7. Chapter 7 — FIRE AND SMOKE PROTECTION FEATURES
  8. Chapter 7A — MATERIALS AND CONSTRUCTION METHODS FOR EXTERIOR W…
  9. Chapter 8 — INTERIOR FINISHES
  10. Chapter 9 — FIRE PROTECTION AND LIFE SAFETY SYSTEMS
  11. Chapter 10 — MEANS OF EGRESS
  12. Chapter 11 — RESERVED
  13. Chapter 11A — HOUSING ACCESSIBILITY
  14. Chapter 11B — ACCESSIBILITY TO PUBLIC BUILDINGS, PUBLIC ACCOMM…
  15. Chapter 12 — INTERIOR ENVIRONMENT
  16. Chapter 13 — ENERGY EFFICIENCY
  17. Chapter 14 — EXTERIOR WALLS
  18. Chapter 15 — ROOF ASSEMBLIES AND ROOFTOP STRUCTURES
  19. Chapter 16 — STRUCTURAL DESIGN
  20. Chapter 16A — STRUCTURAL DESIGN
  21. Chapter 17 — SPECIAL INSPECTIONS AND TESTS
  22. Chapter 17A — SPECIAL INSPECTIONS AND TESTS
  23. Chapter 18 — SOILS AND FOUNDATIONS
  24. Chapter 18A — SOILS AND FOUNDATIONS
  25. Chapter 19 — CONCRETE
  26. Chapter 19A — CONCRETE
  27. Chapter 20 — ALUMINUM
  28. Chapter 21 — MASONRY
  29. Chapter 21A — MASONRY
  30. Chapter 22 — STEEL
  31. Chapter 22A — STEEL
  32. Chapter 23 — WOOD
  33. Chapter 24 — GLASS AND GLAZING
  34. Chapter 25 — GYPSUM PANEL PRODUCTS AND PLASTER
  35. Chapter 26 — PLASTIC
  36. Chapter 27 — ELECTRICAL
  37. Chapter 28 — MECHANICAL SYSTEMS
  38. Chapter 29 — PLUMBING SYSTEMS
  39. Chapter 30 — ELEVATORS AND CONVEYING SYSTEMS
  40. Chapter 31 — SPECIAL CONSTRUCTION
  41. Chapter 31A — SYSTEMS FOR WINDOW CLEANING OR EXTERIOR BUILDING…
  42. Chapter 31B — PUBLIC POOLS
  43. Chapter 31C — RADIATION
  44. Chapter 31D — FOOD ESTABLISHMENTS
  45. Chapter 31F — MARINE OIL TERMINALS
  46. Chapter 32 — ENCROACHMENTS INTO THE PUBLIC RIGHT-OF-WAY
  47. Chapter 33 — SAFEGUARDS DURING CONSTRUCTION
  48. Chapter 34 — RESERVED
  49. Chapter 35 — REFERENCED STANDARDS
  50. Appendix A — EMPLOYEE QUALIFICATIONS
  51. Appendix B — BOARD OF APPEALS
  52. Appendix C — GROUP U—AGRICULTURAL BUILDINGS
  53. Appendix D — FIRE DISTRICTS
  54. Appendix E — RESERVED
  55. Appendix F — RODENTPROOFING
  56. Appendix G — FLOOD-RESISTANT CONSTRUCTION
  57. Appendix H — SIGNS
  58. Appendix I — PATIO COVERS
  59. Appendix J — GRADING
  60. Appendix K — GROUP R-3 AND GROUP R-3.1 OCCUPANCIES PROTECTED B…
  61. Appendix L — EARTHQUAKE RECORDING INSTRUMENTATION
  62. Appendix M — TSUNAMI-GENERATED FLOOD HAZARDS
  63. Appendix N — REPLICABLE BUILDINGS
  64. Appendix O — PERFORMANCE-BASED APPLICATION
  65. Appendix P — SLEEPING LOFTS
  66. Appendix Q — EMERGENCY HOUSING

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