Section 503A

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 construction. Alterations shall be such that the existing build- ing 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 structures in flood hazard areas established in Section 1612 A .3 of the California Building Code, any alteration that constitutes substantial 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 established in Section 1612 A .3 of the California Building Code, 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 replaced or otherwise altered as needed to carry the gravity loads required by this code for new structures. 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 load required by this code for new structures.

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 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 strength- ened, 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 require- ments of Section 503A.3. Any existing element that will form part of the lateral load path for any part of the addition 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 structure, the existing structure and its addition acting together as a single structure shall be shown to meet the requirements of Sections 1609 A and 1613 A of the California Building Code .

Exceptions: For incidental and minor additions:

1. Any existing lateral load-carrying structural element 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 purposes of calculating demand-capacity ratios, the demand shall consider applicable load combinations with design lateral loads or forces in accordance with Sections 1609 A and 1613 A of the California Build- ing Code . For purposes of this exception, comparisons of demand-capacity ratios and calculation 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.

the California Build- ing Code . For purposes of this exception, comparisons of demand-capacity ratios and calculation 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.

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PRESCRIPTIVE COMPLIANCE METHOD

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- uated and designed for live loads approved prior to the alteration. 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 alteration does result in increased design live load, the live load required by Cali- fornia Building Code Section 1607A shall be used.

[BS] 503 A .4 Existing structural elements carrying lateral load. Except as permitted by Section 503 A .13, where the alteration increases design lateral loads in accordance with California Building Code Section 1609A or 1613A, or where the alteration, results in a prohibited structural irregularity as defined in the California Building Code, or where the alter- ation decreases the capacity of any existing lateral loadcarrying structural element, the structure of the altered building or structure shall meet the requirements of Sections 1609 A and 1613 A of the California Building Code .

Exceptions: For incidental and minor alterations:

1. Any existing lateral load-carrying structural element whose demand-capacity ratio with the alteration considered is not more than 10 percent greater than its demand-capacity ratio with the alteration ignored shall be permitted to remain unaltered. For purposes of calculating demand-capacity ratios, the demand shall consider applicable load combinations with design lateral loads or forces in accordance with Sections 1609 A and 1613 A of the California Build- ing Code . Reduced seismic forces shall be permitted. For purposes of this exception, comparisons of demand-capacity ratios and calculation 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.

[BS] 503 A .5 Seismic Design Category F. Not permitted by OSHPD.

[BS] 503 A .6 Bracing for unreinforced masonry parapets on reroofing. Not permitted by OSHPD.

[BS] 503 A .7 Anchorage for concrete and reinforced masonry walls. Not permitted by OSHPD.

[BS] 503 A .8 Anchorage for unreinforced masonry walls in major alterations. Not permitted by OSHPD.

[BS] 503 A .9 Bracing for unreinforced masonry parapets in major alterations. Not permitted by OSHPD.

[BS] 503 A .10 Anchorage of unreinforced masonry parti- tions in major alterations. Not permitted by OSHPD.

[BS] 503 A .11 Substantial structural alteration. Not permit- ted by OSHPD.

[BS] 503 A .12 Roof diaphragms resisting wind loads in high-wind regions. Not permitted by OSHPD.

[BS] 503 A .13 Voluntary seismic improvements . Alterations to existing structural elements or additions of new structural elements that are not otherwise required by this chapter and 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 following:

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 con- nected 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 Building Code Chapter 16A. Demands for new or altered existing structural ele- ments need not exceed the maximum 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 compartments. Shall comply with Califor- nia Building Standards Code.

503 A .15 Refuge areas. Shall comply with California Build- ing Standards Code.

503 A .16 Enhanced classroom acoustics. In Group E occupancies, where the work area exceeds 50 percent of the building area, enhanced classroom acoustics shall be provided in all classrooms with a volume of 20,000 cubic feet (565 m ³ ) or less. Enhanced classroom acoustics shall comply with the reverberation time in Section 808 of ICC A117.1.

503 A .17 Locking arrangements in educational occupan- cies. In Group E occupancies, Group B educational occupancies and Group I-4 occupancies, egress doors with locking arrangements designed to keep intruders from entering the room shall comply with Section 1010.2.8 of the California Building Code .

503 A .18 Two-way communications systems. Where the work area for alterations exceeds 50 percent of the building area and the building has elevator service, a two-way communication systems shall be provided where required by Section 1009.8 of the California Building Code .

503 A .19 Smoke alarms. Shall comply with California Build- ing Standards Code. 503 A .20 Carbon monoxide alarms. Shall comply with Cali- fornia Building Standards Code.