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Appendix BO — EXISTING BUILDINGS AND STRUCTURES

Section BO102 — COMPLIANCE

2025 California Residential Code (Title 24, Part 2.5) · 2025 edition · updated 2026-07-27 · California

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

BO102.1 General.

The work shall not cause the building or structure to become unsafe or adversely affect the performance of the building; shall not cause an existing mechanical or plumbing system to become unsafe, hazardous, insanitary or overloaded; and unless expressly permitted by these provisions, shall not make the building any less compliant with this code or to any previously approved alternative arrangements than it was before the work was undertaken.

BO102.2 Identification of work.

The work shall be clearly identified on the permits issued under these provisions.

BO102.3 Structural.

Structural elements and systems that are altered, repaired or replaced shall comply with Section R102.6.1 and the structural provisions of this appendix. The work performed shall not cause the structure to become less compliant with this code than it was before the work was undertaken.

BO102.3.1 Design loads. The minimum design loads for the structure shall be the loads applicable at the time the building was constructed. The minimum design loads for new structural components shall comply with this code. Structural elements that are uncovered during the course of the alteration and that are found to be unsafe shall be repaired in accordance with Section R102.6.1.

BO102.4 Smoke alarms. Smoke alarms shall be provided where required by Section R310.2.2.

BO102.5 Carbon monoxide alarms.

Carbon monoxide alarms shall be provided where required by Section R311.2.2.

BO102.6 Replacement windows.

Where an existing window, including the sash and glazed portion, or safety glazing is replaced, the replacement window or safety glazing shall comply with the requirements of Sections BO102.6.1 through BO102.6.3, as applicable.

BO102.6.1 Energy efficiency. Replacement windows shall comply with the requirements of Chapter 11.

BO102.6.2 Safety glazing. Replacement glazing in hazardous locations shall comply with the safety glazing requirements of Section R324.

BO102.6.3 Window fall protection. Window fall protection shall be installed in accordance with Section R321.2.

BO102.7 Flood hazard areas.

Work performed in existing buildings located in a flood hazard area as established by Table R301.2 shall be subject to the provisions of Section R104.3.1.

BO102.8 Equivalent alternatives.

Work performed in accordance with the California Existing Building Code shall be deemed to comply with the provisions of this appendix. These provisions are not intended to prevent the use of any alternative material, alternative design or alternative method of construction not specifically prescribed herein, provided that any alternative has been deemed to be equivalent and its use authorized by the building official.

BO102.9 More restrictive requirements.

Buildings or systems in compliance with the requirements of this code for new construction shall not be required to comply with any more restrictive requirement of these provisions.

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▸ Contents — 2025 California Residential Code (Title 24, Part 2.5)
2025 California Residential Code (Title 24, Part 2.5)
  1. Chapter 1 — ADMINISTRATION
  2. Chapter 2 — DEFINITIONS
  3. Chapter 3 — BUILDING PLANNING
  4. Chapter 4 — FOUNDATIONS
  5. Chapter 5 — FLOORS
  6. Chapter 6 — WALL CONSTRUCTION
  7. Chapter 7 — WALL COVERING
  8. Chapter 8 — ROOF-CEILING CONSTRUCTION
  9. Chapter 9 — ROOF ASSEMBLIES
  10. Chapter 10 — CHIMNEYS AND FIREPLACES
  11. Chapter 44 — REFERENCED STANDARDS
  12. Appendix AA — BOARD OF APPEALS
  13. Appendix AB — PERMIT FEES
  14. Appendix AC — RESERVED
  15. Appendix BA — RESERVED
  16. Appendix BB — TINY HOUSES
  17. Appendix BC — RESERVED
  18. Appendix BD — RESERVED
  19. Appendix BE — RADON CONTROL METHODS
  20. Appendix BF — PATIO COVERS
  21. Appendix BG — SOUND TRANSMISSION
  22. Appendix BH — AUTOMATIC VEHICULAR GATES
  23. Appendix BI — LIGHT STRAW-CLAY CONSTRUCTION
  24. Appendix BJ — STRAWBALE CONSTRUCTION
  25. Appendix BK — COB CONSTRUCTION (MONOLITHIC ADOBE)
  26. Appendix BL — HEMP-LIME (HEMPCRETE) CONSTRUCTION
  27. Appendix BM — 3D-PRINTED BUILDING CONSTRUCTION
  28. Appendix BN — EXTENDED PLATE WALL CONSTRUCTION
  29. ▸ Appendix BO — EXISTING BUILDINGS AND STRUCTURES
    Overview
    1. Section BO101 — PURPOSE AND INTENT
    2. Section BO102 — COMPLIANCE
    3. Section BO103 — DEFINITIONS
    4. Section BO104 — REPAIRS
    5. Section BO105 — ALTERATIONS
    6. Section BO106 — ADDITION
    7. Section BO107 — RELOCATED BUILDINGS
    8. Section BO108 — REFERENCED STANDARDS
  30. Appendix CA — RESERVED
  31. Appendix CB — RESERVED
  32. Appendix CC — RESERVED
  33. Appendix CD — RESERVED
  34. Appendix CE — RESERVED
  35. Appendix CF — RESERVED
  36. Appendix CG — NONSEWERED SANITATION SYSTEMS
  37. Appendix CH — PRIVATE SEWAGE DISPOSAL
  38. Appendix CI — SWIMMING POOL SAFETY ACT
  39. Appendix CJ — EMERGENCY HOUSING
  40. Appendix CK — AREAS PROTECTED BY THE FACILITIES OF THE CENTRAL…

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