Section BO105 — ALTERATIONS — 2025 California Residential Code (Title 24, Part 2.5)

BO105.1 General. ¶

BO105.1 General. Alterations to existing buildings shall comply with the provisions of this code for new construction, except as permitted by Sections BO105.2 through BO105.8. Engineered design in accordance with Section R301.1.3 shall be permitted to meet the requirements of this section. Alterations shall not cause the existing building to become less compliant with the provisions of this code for new construction than the existing building was prior to the work.

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BO105.2 Newly constructed elements. ¶

BO105.2 Newly constructed elements. Newly constructed elements, components and systems shall comply with the requirements of this code. Exceptions: 1. Added openable windows are not required to comply with the light and ventilation requirements of Section R325. 2. Newly installed electrical equipment shall comply with the requirements of Section BO105.5.

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

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BO105.3 Nonconformities. ¶

BO105.3 Nonconformities. The work shall not increase the extent of noncompliance or create nonconformity to those requirements that did not previously exist.

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BO105.4 Structural. ¶

BO105.4 Structural. Altered structural elements and systems shall comply with Section R102.6.1 and the structural provisions of this appendix. BO105.4.1 Decreased structural capacity. Where an alteration causes a decrease in capacity in any structural component, that structural component shall be shown to comply or shall be altered to comply with the applicable provisions of Chapters 3, 4, 5, 6 and 8. BO105.4.2 Increased design loads. Where an alteration causes an increase in loads as described in this section, the existing structural components that support the increased load, including the…

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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BO105.5 Electrical equipment and wiring. ¶

BO105.5 Electrical equipment and wiring. Electrical equipment and wiring shall comply with this section. BO105.5.1 Materials and methods. Newly installed electrical equipment and wiring relating to work done in any work area, including in newly installed partitions and ceilings, shall comply with the materials and methods requirements of Chapters 34 through 43. BO105.5.2 Electrical service. Service to the dwelling unit shall be not less than 100 ampere, three-wire capacity, and service equipment shall be dead front having no live parts exposed that could allow accidental contact. Type “S”…

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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BO105.6 Ventilation. ¶

BO105.6 Ventilation. Reconfigured spaces intended for occupancy and spaces converted to habitable or occupiable space in any work area shall be provided with ventilation in accordance with Section R325.

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BO105.7 Ceiling height. ¶

BO105.7 Ceiling height. Where a habitable attic or habitable space is created in an existing building, ceiling heights shall be not less than 6 feet 8 inches (2032 mm). Bathrooms, toilet rooms and laundry rooms shall have a ceiling height of not less than 6 feet 4 inches (1930 mm). Exceptions: 1. For rooms with sloped ceilings, the required floor area of the room shall have a ceiling height of not less than 5 feet (1524 mm), and not less than 50 percent of the required floor area shall have a ceiling height of not less than 6 feet 8 inches (2134 mm). 2. At beams, girders, ducts or other…

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

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BO105.8 Stairs, handrails and guards. ¶

BO105.8 Stairs, handrails and guards. Stairs, handrails and guards shall comply with this section. BO105.8.1 Stair width. Existing basement stairs and handrails not otherwise being altered or modified shall be permitted to maintain their current clear width at, above and below existing handrails. BO105.8.2 Stair headroom. Headroom height on existing basement stairs being altered or modified shall not be reduced below the existing stairway finished headroom. Existing basement stairs not otherwise being altered shall be permitted to maintain the current finished headroom. on Jul 18, 2025 11:14…

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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