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Chapter 4 — SPECIAL DETAILED REQUIREMENTS BASED ON OCCUPANCY AND USE

Section 404 — ATRIUMS

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.

404.1 General.

The provisions of Sections 404.1 through 404.12 shall apply to buildings containing atriums. Atriums are not permitted in buildings or structures classified as Group H.

Exception: Vertical openings that comply with Sections 712.1.1 through 712.1.3, and Sections 712.1.9 through 712.1.14.

404.2 Use.

The floor of the atrium shall not be used for other than low fire hazard uses and only approved materials and decorations in accordance with the California Fire Code shall be used in the atrium space.

Exception: The atrium floor area is permitted to be used for any approved use where the individual space is provided with an automatic sprinkler system in accordance with Section 903.3.1.1.

[F] 404.3 Automatic sprinkler protection. An approved automatic sprinkler system shall be installed throughout the entire building.

Exceptions:

  1. That area of a building adjacent to or above the atrium need not be sprinklered provided that portion of the building is separated from the atrium portion by not less than 2-hour fire barriers constructed in accordance with Section 707 or horizontal assemblies constructed in accordance with Section 711, or both.
  2. Where the ceiling of the atrium is more than 55 feet (16 764 mm) above the floor, sprinkler protection at the ceiling of the atrium is not required.

[F] 404.4 Fire alarm system. A fire alarm system shall be provided in accordance with Section 907.2.14.

4-12 2025 CALIFORNIA BUILDING CODE

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

SPECIAL DETAILED REQUIREMENTS BASED ON OCCUPANCY AND USE

404.5 Smoke control.

A smoke control system shall be installed in accordance with Section 909.

Exceptions:

  1. In other than Group I-2 and R-2.1, Condition 2, smoke control is not required for atriums that connect only two stories.
  2. A smoke control system is not required for atriums connecting more than two stories when all of the following are met: 2.1. Only the two lowest stories shall be permitted to be open to the atrium. 2.2. All stories above the lowest two stories shall be separated from the atrium in accordance with the provisions for a shaft in Section 713.4.

404.6 Enclosure of atriums.

Atrium spaces shall be separated from adjacent spaces by a 1-hour fire barrier constructed in accordance with Section 707 or a horizontal assembly constructed in accordance with Section 711, or both.

Exceptions:

  1. A fire barrier is not required where a glass wall forming a smoke partition is provided. The glass wall shall comply with all of the following: 1.1. Automatic sprinklers are provided along both sides of the separation wall and doors, or on the room side only if there is not a walkway on the atrium side. The sprinklers shall be located between 4 inches and 12 inches (102 mm and 305 mm) away from the glass and at intervals along the glass not greater than 6 feet (1829 mm). The sprinkler system shall be designed so that the entire surface of the glass is wet upon activation of the sprinkler system without obstruction. 1.2. The glass wall shall be installed in a gasketed frame in a manner that the framing system deflects without breaking (loading) the glass before the sprinkler system operates. 1.3. Where glass doors are provided in the glass wall, they shall be either self-closing or automatic-closing.
  2. A fire barrier is not required where a glass-block wall assembly complying with Section 2110 and having a [3] / 4 -hour fire protection rating is provided.
  3. In other than Group I and R-2.1 occupancies, a fire barrier is not required between the atrium and the adjoining spaces of up to three floors of the atrium provided that such spaces are accounted for in the design of the smoke control system.
  4. In other than Group I and R-2.1 occupancies, a fire barrier is not required between the atrium and the adjoining spaces where the atrium is not required to be provided with a smoke control system.
  5. In Group I-2 and R-2.1 occupancies, a fire barrier is not required between the atrium and the adjoining spaces, other than care recipient sleeping or treatment rooms, for up to three stories of the atrium provided that such spaces are accounted for in the design of the smoke control system and do not provide access to care recipient sleeping or treatment rooms.
  6. A horizontal assembly is not required between the atrium and openings for escalators complying with Section 712.1.3.
  7. A horizontal assembly is not required between the atrium and openings for exit access stairways and ramps complying with Item 4 of Section 1019.3.

[F] 404.7 Standby power. Equipment required to provide smoke control shall be provided with standby power in accordance with Section 909.11.

404.8 Interior finish.

The interior finish of walls and ceilings of the atrium shall be not less than Class B. Sprinkler protection shall not result in a reduction in class.

[BE] 404.9 Exit access travel distance. Exit access travel distance for areas open to an atrium shall comply with the requirements of Section 1017.

[BE] 404.10 Exit stairways in an atrium. Where an atrium contains an interior exit stairway all the following shall be met:

  1. The entry to the exit stairway is the edge of the closest riser of the exit stairway.
  2. The entry of the exit stairway shall have access from a minimum of two directions.
  3. The distance between the entry to an exit stairway in an atrium and the entrance to a minimum of one exit stairway enclosed in accordance with Section 1023.2 shall comply with the separation required by Section 1007.1.1.
  4. Exit access travel distance shall be measured to the closest riser of the exit stairway.
  5. Not more than 50 percent of the exit stairways shall be located in the same atrium.
  6. The discharge from the exit stairway at the level of exit discharge shall comply with Section 1028.1.

[BE] 404.11 Interior exit stairway discharge. Discharge of interior exit stairways through an atrium shall be in accordance with Section 1028.

404.12 Group I and R-2.1 occupancy means of egress.

Required means of egress from sleeping and treatment rooms in Group I and R-2.1 occupancies shall not pass through the atrium.

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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…
    Overview
    1. Section 401 — SCOPE
    2. Section 402 — COVERED MALL AND OPEN MALL BUILDINGS
    3. Section 403 — HIGH-RISE BUILDINGS AND GROUP I-2 OCCUPANCIES HA…
    4. Section 404 — ATRIUMS
    5. Section 405 — UNDERGROUND BUILDINGS
    6. Section 406 — MOTOR-VEHICLE-RELATED OCCUPANCIES
    7. Section 407 — GROUP I-2
    8. Section 408 — GROUP I-3
    9. Section 409 — MOTION PICTURE PROJECTION ROOMS
    10. Section 410 — STAGES, PLATFORMS AND TECHNICAL PRODUCTION AREAS
    11. Section 411 — SPECIAL AMUSEMENT AREAS
    12. Section 412 — AIRCRAFT-RELATED OCCUPANCIES
    13. Section 413 — COMBUSTIBLE STORAGE
    14. Section 414 — HAZARDOUS MATERIALS
    15. Section 415 — GROUPS H-1, H-2, H-3, H-4 AND H-5
    16. Section 416 — SPRAY APPLICATION OF FLAMMABLE FINISHES
    17. Section 417 — DRYING ROOMS
    18. Section 418 — ORGANIC COATINGS
    19. Section 419 — ARTIFICIAL DECORATIVE VEGETATION
    20. Section 420 — GROUPS R-1, R-2, R-2.1, R-2.2, R-3, R-3.1 AND R-4
    21. Section 421 — HYDROGEN FUEL GAS ROOMS
    22. Section 422 — AMBULATORY CARE FACILITIES
    23. Section 423 — STORM SHELTERS
    24. Section 424 — PLAY STRUCTURES
    25. Section 425 — HYPERBARIC FACILITIES
    26. Section 427 — MEDICAL GAS SYSTEMS
    27. Section 435 — SPECIAL PROVISIONS FOR LICENSED 24-HOUR CARE FAC…
    28. Section 436 — GROUP I-4 [SFM]
    29. Section 437 — RESERVED
    30. Section 438 — RESERVED
    31. Section 439 — ROAD TUNNELS, BRIDGES AND OTHER LIMITED-ACCESS H…
    32. Section 440 — HORSE RACING STABLES [SFM]
    33. Section 441 — PET KENNELS AND PET BOARDING FACILITIES [SFM]
    34. Section 442 — COMBUSTION ENGINES AND GAS TURBINES [SFM]
    35. Section 443 — FIXED GUIDEWAY TRANSIT AND PASSENGER RAIL SYSTEM…
    36. Section 444 — EXPLOSIVES [SFM]
    37. Section 445 — RESERVED
    38. Section 446 — WINERY CAVES [SFM]
    39. Section 447 — RESERVED
    40. Section 448 — RESERVED
    41. Section 449 — PUBLIC LIBRARIES [SL AND SFM]
    42. Section 450 — GROUP C [SFM]
    43. Section 451 — RESERVED
    44. Section 452 — SCHOOL FACILITIES FOR KINDERGARTEN THROUGH 12TH …
    45. Section 453 — GROUP L [SFM]
    46. Section 454 — RESERVED
    47. Section 455 — LARGE FAMILY DAY-CARE HOMES [SFM]
  5. Chapter 5 — GENERAL BUILDING HEIGHTS AND AREAS
  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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