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Chapter 3 — PROVISIONS FOR ALL COMPLIANCE METHODS

Section 304 — STRUCTURAL DESIGN LOADS AND EVALUATION AND DESIGN PROCEDURES

2025 California Existing Building Code (Title 24, Part 10) · 2025 edition · updated 2026-07-29 · California

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

[BS] 304.1 Live loads. Where an addition or alteration does not result in increased design live load, existing gravity load-carrying structural elements shall be permitted to be evaluated and designed for live loads approved prior to the addition or alteration. If the approved live load is less than that required by Section 1607 of the California Building Code, the area designated for the nonconforming live load shall be posted with placards of approved design indicating the approved live load. Where the addition or alteration results in increased design live load, the live load required by Section 1607 of the California Building Code shall be used.

[BS] 304.2 Snow loads on adjacent buildings. Where an alteration or addition changes the potential snow drift effects on an adjacent building, the code official is authorized to enforce Section 7.12 of ASCE 7.

[BS] 304.3 Seismic evaluation and design procedures. Where required, seismic evaluation or design shall comply with the procedures and criteria in this section, regardless of which compliance method is used. The scope of the required evaluation or design shall be as indicated in applicable provisions of Chapters 4 through 11 .

[BS] 304.3.1 Full seismic criteria. Where required, seismic evaluation or design shall comply with one of the following methodologies, which shall not be applied in combination with each other:

  1. Section 1613 of the California Building Code . Where the existing seismic force-resisting system is a type that can be designated as “Ordinary,” values of R, Ω 0 and C d used for analysis in accordance with Chapter 16 of the California Building Code shall be those specified for structural systems classified as “Ordinary” in accordance with Table 12.2-1 of ASCE 7, unless it can be demonstrated that the structural system will provide performance equivalent to that of a “Detailed,” “Intermediate” or “Special” system.
  2. ASCE 41, using a Tier 3 procedure and both levels of the two-level performance objective in Table 304.3.1 for the applicable risk category.

[BS] TABLE 304.3.1—PERFORMANCE OBJECTIVES FOR USE IN ASCE 41 FOR COMPLIANCE WITH FULL SEISMIC CRITERIA

RISK CATEGORY
(Based on IBC Table 1604.5)		 STRUCTURAL PERFORMANCE LEVEL FOR USE
WITH BSE-1N EARTHQUAKE HAZARD LEVEL		 STRUCTURAL PERFORMANCE LEVEL FOR USE
WITH BSE-2N EARTHQUAKE HAZARD LEVEL
I Life Safety (S-3) Collapse Prevention (S-5)
II Life Safety (S-3) Collapse Prevention (S-5)
III Damage Control (S-2) Limited Safety (S-4)
IV Immediate Occupancy (S-1) Life Safety (S-3)

[BS] 304.3.2 Reduced seismic criteria. Where required, seismic evaluation or design shall comply with one of the following methodologies, which shall not be applied in combination with each other:

  1. Section 1613 of the California Building Code using 75 percent of the prescribed forces. Values of R, Ω 0 and C d used for analysis shall be as specified in Section 304.3.1 of this code.

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

PROVISIONS FOR ALL COMPLIANCE METHODS

  1. Applicable chapters of Appendix A of this code, for structures or portions of structures specified in Items 2.1 through 2.4 subject to the limitations of the respective chapter. 2.1. Chapter A1 for unreinforced masonry bearing wall buildings assigned to Risk Category I or II. 2.2. Chapter A2 for the wall anchorage system in reinforced concrete and reinforced masonry wall buildings with flexible diaphragms assigned to Risk Category I or II. 2.3. Chapter A3 for cripple walls and sill plate anchorage in residential buildings of light-frame wood construction assigned to Risk Category I or II. 2.4. Chapter A4 for soft, weak or open-front wall conditions in multiple-unit residential buildings of wood construction assigned to Risk Category I or II.

  2. ASCE 41, using the performance objective in Table 304.3.2 for the applicable risk category.

  3. Chapter A3 for cripple walls and sill plate anchorage in residential buildings of light-frame wood construction assigned to Risk Category I or II. 2.4. Chapter A4 for soft, weak or open-front wall conditions in multiple-unit residential buildings of wood construction assigned to Risk Category I or II.

  4. ASCE 41, using the performance objective in Table 304.3.2 for the applicable risk category.

[BS] TABLE 304.3.2—PERFORMANCE OBJECTIVES FOR USE IN ASCE 41 FOR COMPLIANCE WITH REDUCED CRITERIA FORCES

RISK CATEGORY
(Based on IBC Table 1604.5)		 STRUCTURAL PERFORMANCE LEVEL FOR USE
WITH BSE-1E EARTHQUAKE HAZARD LEVEL		 STRUCTURAL PERFORMANCE LEVEL FOR USE
WITH BSE-2E EARTHQUAKE HAZARD LEVEL
I Life Safety (S-3).
See Note a		 Collapse Prevention (S-5)
II Life Safety (S-3).
See Note a		 Collapse Prevention (S-5)
III Damage Control (S-2).
See Note a		 Limited Safety (S-4).
See Note b
IV Immediate Occupancy (S-1) Life Safety (S-3).
See Note c
a. For Risk Categories I, II and III, the Tier 1 and Tier 2 procedures need not be considered for the BSE-1E earthquake hazard level.
b. For Risk Category III, the Tier 1 screening checklists shall be based on the Collapse Prevention, except that checklist statements using the Quick Check provisions shall be
based on_MS_-factors that are the average of the values for Collapse Prevention and Life Safety.
c. For Risk Category IV, the Tier 1 screening checklists shall be based on Collapse Prevention, except that checklist statements using the Quick Check provisions shall be based
on_MS_-factors for Life Safety.

304.3.3 Criteria for incidental and minor structural alteration, additions, or repairs of pre-1973 code buildings. [OSHPD 1R, 2, 4 & 5] Provisions of this section shall apply to hospital buildings which were originally designed to pre-1973 building codes, and had no major structural alterations, additions or repairs using 1973 California Building Standards Code or later editions with an OSHPD permit. 1. Nonstructural components. Component importance factor, I p , shall be permitted to be 1.0. Exception: Components required for life safety purposes after an earthquake, including emergency, standby or alternative power systems, mechanical smoke removal systems, fire protection sprinkler systems, fire alarm control panels and egress stairways shall have a component importance factor (I p ) of 1.5.

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▸ Contents — 2025 California Existing Building Code (Title 24, Part 10)
2025 California Existing Building Code (Title 24, Part 10)
  1. Chapter 1 — ADMINISTRATION
  2. Chapter 2 — DEFINITIONS
  3. ▸ Chapter 3 — PROVISIONS FOR ALL COMPLIANCE METHODS
    Overview
    1. Section 301 — ADMINISTRATION
    2. Section 302 — GENERAL PROVISIONS
    3. Section 303 — STORM SHELTERS
    4. Section 304 — STRUCTURAL DESIGN LOADS AND EVALUATION AND DESIG…
    5. Section 305 — IN-SITU LOAD TESTS
    6. Section 306 — ACCESSIBILITY FOR EXISTING BUILDINGS
    7. Section 307 — SMOKE ALARMS
    8. Section 308 — CARBON MONOXIDE DETECTION
    9. Section 309 — ADDITIONS AND REPLACEMENTS OF EXTERIOR WALL COVE…
    10. Section 310 — [OSHPD 1R, 2 AND 5]—SERVICES/SYSTEMS AND UTILITIES
    11. Section 311 — [OSHPD 1R, 2 AND 5]—MEANS OF EGRESS
    12. Section 312 — [OSHPD 1R]—HOSPITAL SPC AND FREESTANDING BUILDIN…
    13. Section 313 — [SFM]—EXISTING GROUP R-1 AND GROUP R-2 OCCUPANCIES
    14. Section 314 — [SFM]—EXISTING HIGH-RISE BUILDINGS
    15. Section 315 — [SFM]—EXISTING GROUP I OCCUPANCIES
    16. Section 316 — [SFM]—EXISTING GROUP L OCCUPANCIES
    17. Section 317 — [BSC, DSA-SS & DSA-SS/CC]—EARTHQUAKE EVALUATION …
    18. Section 318 — [BSC, DSA-SS & DSA-SS/CC]—DEFINITIONS
    19. Section 319 — [BSC, DSA-SS & DSA-SS/CC]—SEISMIC CRITERIA SELEC…
    20. Section 320 — [BSC, DSA-SS & DSA-SS/CC]—METHOD A
    21. Section 321 — [BSC, DSA-SS & DSA-SS/CC]—METHOD B
    22. Section 322 — [BSC, DSA-SS & DSA-SS/CC]—PEER REVIEW REQUIREMENTS
    23. Section 323 — [DSA-SS, DSA-SS/CC]—ADDITIONAL REQUIREMENTS FOR …
  4. Chapter 3A — PROVISIONS FOR ALL COMPLIANCE METHODS
  5. Chapter 4 — REPAIRS
  6. Chapter 4A — REPAIRS
  7. Chapter 5 — PRESCRIPTIVE COMPLIANCE METHOD
  8. Chapter 5A — PRESCRIPTIVE COMPLIANCE METHOD
  9. Chapter 6 — CLASSIFICATION OF WORK
  10. Chapter 7 — ALTERATIONS—LEVEL 1
  11. Chapter 8 — ALTERATIONS—LEVEL 2
  12. Chapter 9 — ALTERATIONS—LEVEL 3
  13. Chapter 10 — CHANGE OF OCCUPANCY
  14. Chapter 11 — ADDITIONS
  15. Chapter 12 — HISTORIC BUILDINGS
  16. Chapter 13 — PERFORMANCE COMPLIANCE METHODS
  17. Chapter 14 — RELOCATED OR MOVED BUILDINGS
  18. Chapter 15 — CONSTRUCTION SAFEGUARDS
  19. Chapter 16 — REFERENCED STANDARDS
  20. Appendix A — GUIDELINES FOR THE SEISMIC RETROFIT OF EXISTING B…
  21. Appendix B — SUPPLEMENTARY ACCESSIBILITY REQUIREMENTS FOR EXIS…
  22. Appendix C — GUIDELINES FOR THE WIND RETROFIT OF EXISTING BUIL…
  23. Appendix D — BOARD OF APPEALS
  24. Appendix E — TEMPORARY EMERGENCY USES
  25. Appendix A — GUIDELINES ON FIRE RATINGS OF ARCHAIC MATERIALS A…

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