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Chapter 5 — PRESCRIPTIVE COMPLIANCE METHOD

Section 503A

California Existing Building Code (Title 24, Part 10) · 2019 edition · updated 2026-09-10 · California

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

ALTERATIONS 503 A .1 General. Except as provided by this section, alter- ations to any building or structure shall comply with the requirements of the California Building Code for new con- struction. Alterations shall be such that the existing building or structure is no less conforming with the provisions of this code than the existing building or structure was prior to the alteration.

Exceptions:

1. An existing stairway shall not be required to comply with the requirements of California Building Code Section 1011 where the existing space and construc- tion does not allow a reduction in pitch or slope.

2. Handrails otherwise required to comply with Cali- fornia Building Code Section 1011.11 shall not be required to comply with the requirements of Califor- nia Building Code Section 1014.6 regarding full extension of the handrails where such extensions would be hazardous due to plan configuration.

[BS] 503 A .2 Flood hazard areas. For buildings and struc- tures in flood hazard areas established in California Building Code Section 1612A.3, any alteration that constitutes sub- stantial improvement of the existing structure, as defined in Chapter 2, shall comply with the flood design requirements for new construction, and all aspects of the existing structure shall be brought into compliance with the requirements for new construction for flood design.

For buildings and structures in flood hazard areas estab- lished in California Building Code Section 1612A.3, any alterations that do not constitute substantial improvement of the existing structure, as defined in Chapter 2, are not required to comply with the flood design requirements for new construction.

[BS] 503 A .3 Existing structural elements carrying gravity load. Any existing gravity load-carrying structural element for which an alteration causes an increase in design gravity load of more than 5 percent shall be strengthened, supple- mented, replaced or otherwise altered as needed to carry the increased gravity load required by this code for new struc- tures. Any existing gravity load-carrying structural element whose gravity load-carrying capacity is decreased as part of the alteration shall be shown to have the capacity to resist the applicable design gravity loads required by this code for new structures.

503A.3.1 Design live load. Where the alteration does not result in increased design live load, existing gravity load carrying structural elements shall be permitted to be eval-

additions that do not constitute substantial improvement of the existing structure, as defined in Chapter 2, are not required to comply with the flood design requirements for new construction.

[BS] 502 A .4 Existing structural elements carrying gravity load. Any existing gravity load-carrying structural element for which an addition and its related alterations cause an increase in design gravity load of more than 5 percent shall be strengthened, supplemented, replaced or otherwise altered as needed to carry the increased gravity load required by this code for new structures. Any existing gravity load-carrying structural element whose gravity load-carrying capacity is decreased shall be considered an altered element subject to the requirements of Section 503A.3. Any existing element that will form part of the lateral load path for any part of the addi- tion shall be considered an existing lateral load-carrying structural element subject to the requirements of Section 502A.5.

502A.4.1 Design live load. Where the addition does not result in increased design live load, existing gravity load- carrying structural elements shall be permitted to be eval- uated and designed for live loads approved prior to the addition. If the approved live load is less than that required by California Building Code Section 1607A, the area designed for the nonconforming live load shall be posted with placards of approved design indicating the approved live load. Where the addition does result in increased design live load, the live load required by Cali- fornia Building Code Section 1607A shall be used.

[BS] 502 A .5 Existing structural elements carrying lateral load. Where the addition is structurally independent of the existing structure, existing lateral load-carrying structural elements shall be permitted to remain unaltered. Where the addition is not structurally independent of the existing struc- ture, the existing structure and its addition acting together as a single structure shall be shown to meet the requirements of California Building Code Sections 1609A and 1613A.

Exceptions: For incidental and minor additions:

1. Any existing lateral load-carrying structural ele- ment whose demand-capacity ratio with the addition considered is no more than 10 percent greater than its demand-capacity ratio with the addition ignored shall be permitted to remain unaltered. For pur- poses of calculating demand-capacity ratios, the demand shall consider applicable load combina- tions with design lateral loads or forces in accor- dance with California Building Code Sections 1609A and 1613A. For purposes of this exception, comparisons of demand-capacity ratios and calcu- lation of design lateral loads, forces and capacities shall account for the cumulative effects of additions and alterations since original construction.

2. Drift limits based on original design code shall be permitted to be used in lieu of the drift limits required by ASCE 7.

Copyright © 2019 ICC. ALL RIGHTS RESERVED. Accessed by Kevin Day (kevin.day@dgs.ca.gov), (California Building Standards Commission) Order Number #100735044 on Jul 24, 2019 03:54 PM (PDT) pursuant to License Agreement with ICC. No further reproduction or distribution authorized. Single user only, copying and networking prohibited. ANY UNAUTHORIZED REPRODUCTION OR DISTRIBUTION IS A VIOLATION OF THE FEDERAL COPYRIGHT ACT AND THE LICENSE AGREEMENT, AND SUBJECT TO CIVIL AND CRIMINAL PENALTIES THEREUNDER.

100735044

are initiated for the purpose of improving the performance of the seismic force-resisting system of an existing structure or the performance of seismic bracing or anchorage of existing nonstructural elements shall be permitted, provided that an engineering analysis is submitted demonstrating the follow- ing:

1. The altered structure, and the altered structural and nonstructural elements are no less conforming with the provisions of this code with respect to earthquake design than they were prior to the alteration.

2. New structural elements are designed, detailed and connected to the existing structural elements as required by California Building Code Chapter 16A. Alterations of existing structural elements shall be based on design demand required by California Build- ing Code Chapter 16A. Demands for new or altered existing structural elements need not exceed the maxi- mum load effect that can be transferred to the elements by the system.

3. New, relocated or altered nonstructural elements are designed, detailed and connected to existing or new structural elements as required by California Building Code Chapter 16A.

4. The alterations do not create a structural irregularity as defined in ASCE 7 or make an existing structural irregularity more severe . 503 A .14 Smoke alarms. Shall comply with California Build- ing Standards Code.

503 A .15 Carbon monoxide alarms. Shall comply with Cali- fornia Building Standards Code. 503 A .16 Refuge areas. Shall comply with California Build- ing Standards Code.

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▸Contents — California Existing Building Code (Title 24, Part 10)
California Existing Building Code (Title 24, Part 10)
  1. Chapter 2 — DEFINITIONS
  2. Appendix A — GUIDELINES FOR
  3. Appendix B — SUPPLEMENTARY
  4. Appendix C — GUIDELINES FOR THE
  5. Chapter 1 — SCOPE AND ADMINISTRATION
  6. Chapter 3 — PROVISIONS FOR ALL COMPLIANCE METHODS
  7. Chapter 4 — REPAIRS
  8. ▸Chapter 5 — PRESCRIPTIVE COMPLIANCE METHOD
    Overview
    1. Section 501
    2. Section 502
    3. Section 503
    4. Section 505
    5. Section 504
    6. Section 506
    7. Section 507
    8. Section 501A
    9. Section 502A
    10. Section 503A
    11. Section 504A
    12. Section 505A
    13. Section 506A
    14. Section 507A
  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

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