Section 503 — ALTERATIONS — 2025 California Existing Building Code (Title 24, Part 10)

503.1 General. ¶

503.1 General. Alterations to any building or structure shall comply with the requirements of the California Building Code or Califor- nia Residential Code, as applicable, for new construction. Alterations shall be such that the existing building or structure is not less complying with the provisions of the California Building Code or California Residential Code, as applicable, than the existing building or structure was prior to the alteration, except that the structural elements need only comply with Sections 503.2 through 503.12. Exceptions: 1. An existing stairway shall not be required to…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use

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503.14 Smoke compartments. ¶

503.14 Smoke compartments. In Group I-2 occupancies where the alteration is on a story used for sleeping rooms for more than 30 care recipients, the story shall be divided into not less than two compartments by smoke barrier walls in accordance with Section 407.5 of the California Building Code as required for new construction.

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503.15 Refuge areas. ¶

503.15 Refuge areas. Where alterations affect the configuration of an area utilized as a refuge area, the capacity of the refuge area shall not be reduced below the required capacity of the refuge area for horizontal exits in accordance with Section 1026.4 of the Cali- fornia Building Code . Where the horizontal exit also forms a smoke compartment, the capacity of the refuge area for Group I-2 and I-3 occupancies and ambulatory care facilities shall not be reduced below that required in Sections 407.5.3, 408.6.2, 420.6.1 and 422.3.2 of the California Building Code, as applicable.

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height

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503.16 Group R-2.1 occupancies. ¶

503.16 Group R-2.1 occupancies. Group R-2.1 occupancies that are being altered and where the work area is greater than 50 percent of the aggregate building area shall be classified in accordance with Section 310.3.1 of the California Building Code . 503.16.1 Smoke Barriers in Group R-2.1 , Condition 2. In Group R-2.1 occupancies where the work area is on a story used for sleeping rooms for more than 30 care recipients, the story shall be divided into not less than two compartments by smoke barrier walls in accordance with Section 420.6 of the California Building Code .

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling

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503.17 Ambulatory care facilities. ¶

503.17 Ambulatory care facilities. Where a work area exceeds 50 percent of the building area and the work area includes an existing ambulatory care facility, the following shall be provided: 1. A smoke compartment in accordance with Section 422.3 of the California Building Code where the alteration results in an ambulatory care facility greater than 10,000 square feet on one story. 2. Separation from adjacent spaces in accordance with Section 422.2 of the California Building Code, where any such facility has the potential for four or more care recipients are to be incapable of…

provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application requirement review coverage subject setback occupancy development standard accessory yard section structure compliance use provision permitted lot commission district approval parking minimum height dwelling application

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503.18 Enhanced classroom acoustics. ¶

503.18 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.

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503.19 Locking arrangements in educational occupancies. ¶

503.19 Locking arrangements in educational occupancies. In Group E occupancies, Group B educational occupancies and Group I4 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 .

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503.20 Two-way communications systems. ¶

503.20 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 Califor- nia Building Code .

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