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Chapter 9 — ALTERATIONS—LEVEL 3

Section 906 — STRUCTURAL

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] 906.1 General. Where buildings are undergoing Level 3 alterations, the provisions of this section shall apply.

[BS] 906.2 Existing structural elements resisting lateral loads. Where work involves a substantial structural alteration,the lateral load-resisting system of the altered building shall be shown to satisfy the requirements of Section 1609 of the California Building Code and Section 304.3.2 of this code. Where the building is assigned to Seismic Design Category D or F, supports and attachments for nonstructural components required to serve any portion of the building with a use included in Risk Category IV shall comply with Section 1613 of the California Building Code or shall comply with ASCE 41 using an objective of Position Retention nonstructural performance with the BSE-1E earthquake hazard level.

Exceptions:

  1. Buildings of Group R occupancy with not more than five dwelling or sleeping units used solely for residential purposes that are altered based on the conventional light-frame construction methods of the California Building Code or in compliance with the provisions of the California Residential Code .
  2. Where the intended alteration involves only the lowest story of a building, structural components of the lateral load resisting system above that story need not comply with this section.

[BS] 906.3 Seismic Design Category F. Where the building is assigned to Seismic Design Category F, the lateral force-resisting system of the altered building shall meet the requirements of Section 1609 of the California Building Code and Section 304.3.2 of this code. Supports and attachments for nonstructural components serving any portion of the building with a use included in Risk Cate- gory IV shall comply with Section 1613 of the California Building Code or shall comply with ASCE 41 using an objective of Position Retention nonstructural performance with the BSE-1E earthquake hazard level.

[BS] 906.4 Anchorage for concrete and masonry buildings. For any building assigned to Seismic Design Category D, E or F with a structural system that includes concrete or reinforced masonry walls with a flexible roof diaphragm, the alteration shall comply with Section 304.3.2 by evaluation of the existing condition or by installation of wall anchors at the roof line of all subject buildings and at the floor lines of unreinforced masonry.

[BS] 906.5 Anchorage for unreinforced masonry walls. For any building assigned to Seismic Design Category C, D, E or F with a structural system that includes unreinforced masonry bearing walls, the alteration shall comply with Section 304.3.2 by evaluation of the existing condition or by installation of wall anchors at the roof line.

[BS] 906.6 Bracing for unreinforced masonry parapets. Parapets constructed of unreinforced masonry in buildings assigned to Seismic Design Category C, D, E or F shall comply with Section 304.3.2 by evaluation of the existing condition or by installation of parapet bracing.

[BS] 906.7 Anchorage of unreinforced masonry partitions. Where the building is assigned to Seismic Design Category C, D, E or F, unreinforced masonry partitions and nonstructural walls within the work area and adjacent to egress paths from the work area shall have their existing conditions evaluated or shall be anchored, removed or altered to resist out-of-plane seismic forces to comply with Section 304.3.2.

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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
  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
    Overview
    1. Section 901 — GENERAL
    2. Section 902 — SPECIAL USE AND OCCUPANCY
    3. Section 903 — BUILDING ELEMENTS AND MATERIALS
    4. Section 904 — FIRE PROTECTION
    5. Section 905 — MEANS OF EGRESS
    6. Section 906 — STRUCTURAL
    7. Section 907 — ENERGY CONSERVATION
    8. Section 908 — EMERGENCY RESPONDER COMMUNICATIONS ENHANCEMENT S…
  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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