Section 503

503.1 General. Except as provided by Section 302.4, 302.5¶

or this section, alterations to any building or structure shall comply with the requirements of the California Building Code or California 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,

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as applicable, than the existing building or structure was prior to the alteration.

Exceptions:

An existing stairway shall not be required to comply with the requirements of Section 1011 of the Cali- fornia Building Code where the existing space and construction does not allow a reduction in pitch or slope.
Handrails otherwise required to comply with Section 1011.11 of the California Building Code shall not be required to comply with the requirements of Section 1014.6 of the California Building Code regarding full extension of the handrails where such extensions would be hazardous because of plan configuration.
Where provided in below-grade transportation stations, existing and new escalators shall have a clear width of less than 32 inches (815 mm).
[BSC] For state-owned buildings, including those owned by the University of California and the Cali- fornia State University and the judicial council, the requirements of Sections 503.3 through 503.4 are replaced by the requirements of Sections 317 through 322.

[BS] 503.2 Flood hazard areas. For buildings and structures in flood hazard areas established in Section 1612.3 of the California Building Code, or Section R322 of the California Residential Code, as applicable, any alteration that constitutes substantial improvement of the existing structure 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 1612.3 of the California Building Code, or Section R322 of the California Residential Code, as applicable, any alterations that do not constitute substantial improvement of the existing structure are not required to comply with the flood design requirements for new construction.

[BS] 503.3 Existing structural elements carrying gravity load. Any existing gravity load-carrying structural element for which an alteration causes an increase in design dead, live or snow load, including snow drift effects, of more than 5 percent shall be replaced or altered as needed to carry the gravity loads required by the California Building 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 dead, live and snow loads including snow drift effects required by the California Building Code for new structures.

Exceptions:

Buildings of Group R occupancy with not more than five dwelling or sleeping units used solely for residential purposes where the altered building complies with the conventional light-frame construction

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methods of the California Building Code or the provisions of the California Residential Code .

Buildings in which the increased dead load is due entirely to the addition of a second layer of roof covering weighing 3 pounds per square foot (0.1437 kN/m ² ) or less over an existing single layer of roof covering. [DSA-SS, DSA-SS/CC] Exception 2 is not permitted.

[BS] 503.4 Existing structural elements carrying lateral load. Except as permitted by Section 503.13, where the alteration increases design lateral loads, results in a prohibited structural irregularity as defined in ASCE 7, or decreases the capacity of any existing lateral load-carrying structural element, the structure of the altered building or structure shall meet the requirements of Sections 1609 and 1613 of the Cali- fornia Building Code . Reduced seismic forces shall be permitted.

Exception: 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 and 1613 of the Califor- nia Building 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.

[BS] 503.5 Seismic Design Category F. Where the work area exceeds 50 percent of the building area, and where the building is assigned to Seismic Design Category F, the structure of the altered building shall meet the requirements of Sections 1609 and 1613 of the California Building Code . Reduced seismic forces shall be permitted.

[BS] 503.6 Bracing for unreinforced masonry parapets on reroofing. Where the intended alteration requires a permit for reroofing and involves removal of roofing materials from more than 25 percent of the roof area of a building assigned to Seismic Design Category D, E or F that has parapets constructed of unreinforced masonry, the work shall include installation of parapet bracing to resist out-of-plane seismic forces, unless an evaluation demonstrates compliance of such items. Reduced seismic forces shall be permitted.

[BS] 503.7 Anchorage for concrete and reinforced masonry walls. Where the work area exceeds 50 percent of the building area, the building is assigned to Seismic Design Category C, D, E or F and the building’s structural system includes concrete or reinforced masonry walls with a flexible roof diaphragm, the alteration work shall include installation of wall anchors at the roof line, unless an evaluation demonstrates compliance of existing wall anchorage. Use of reduced seismic forces shall be permitted.

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[BS] 503.8 Anchorage for unreinforced masonry walls in major alterations. Where the work area exceeds 50 percent of the building area, the building is assigned to Seismic Design Category C, D, E or F and the building’s structural system includes unreinforced masonry bearing walls, the alteration work shall include installation of wall anchors at the floor and roof lines, unless an evaluation demonstrates compliance of existing wall anchorage. Reduced seismic forces shall be permitted.

[BS] 503.9 Bracing for unreinforced masonry parapets in major alterations. Where the work area exceeds 50 percent of the building area, and where the building is assigned to Seismic Design Category C, D, E or F, parapets constructed of unreinforced masonry shall have bracing installed as needed to resist out-of-plane seismic forces, unless an evaluation demonstrates compliance of such items. Reduced seismic forces shall be permitted.

[BS] 503.10 Anchorage of unreinforced masonry parti- tions in major alterations. Where the work area exceeds 50 percent of the building area, and where the building is assigned to Seismic Design Category C, D, E or F, unreinforced masonry partitions and nonstructural walls within the work area and adjacent to egress paths from the work area shall be anchored, removed or altered to resist out-of-plane seismic forces, unless an evaluation demonstrates compliance of such items. Use of reduced seismic forces shall be permitted.

ilding area, and where the building is assigned to Seismic Design Category C, D, E or F, unreinforced masonry partitions and nonstructural walls within the work area and adjacent to egress paths from the work area shall be anchored, removed or altered to resist out-of-plane seismic forces, unless an evaluation demonstrates compliance of such items. Use of reduced seismic forces shall be permitted.

[BS] 503.11 Substantial structural alteration. Where the work area exceeds 50 percent of the building area and where work involves a substantial structural alteration, the lateral load-resisting system of the altered building shall satisfy the requirements of Sections 1609 and 1613 of the California Building Code . Reduced seismic forces shall be permitted.

Exceptions:

Buildings of Group R occupancy with not more than five dwelling or sleeping units used solely for residential purposes that are altered based on the conventional light-frame construction methods of the California Building Code or in compliance with the provisions of the California Residential Code .
Where the intended alteration involves only the lowest story of a building, only the lateral load-resisting components in and below that story need comply with this section.

[BS] 503.12 Roof diaphragms resisting wind loads in high- wind regions. Where the intended alteration requires a permit for reroofing and involves removal of roofing materials from more than 50 percent of the roof diaphragm of a building or section of a building located where the ultimate design wind speed is greater than 115 mph (51 m/s) in accordance with Figure 1609.3(1) of the California Building Code or in a special wind region as defined in Section 1609 of the Califor- nia Building Code, roof diaphragms, connections of the roof diaphragm to roof framing members, and roof-to-wall connections shall be evaluated for the wind loads specified in Section 1609 of the California Building Code, including wind uplift. If the diaphragms and connections in their current condition are not capable of resisting 75 percent of those wind

loads, they shall be replaced or strengthened in accordance with the loads specified in Section 1609 of the California Building Code .

[BS] 503.13 Voluntary lateral force-resisting system alterations. Structural alterations that are intended exclusively to improve the lateral force-resisting system and are not required by other sections of this code shall not be required to meet the requirements of Section 1609 or Section 1613 of the California Building Code, provided that all of the following apply:

The capacity of existing structural systems to resist forces is not reduced.
New structural elements are detailed and connected to existing or new structural elements as required by the California Building Code for new construction.
New or relocated nonstructural elements are detailed and connected to existing or new structural elements as required by the California Building Code for new construction.
The alterations do not create a structural irregularity as defined in ASCE 7 or make an existing structural irregularity more severe.

503.14 Smoke alarms.¶

Individual sleeping units and individual dwelling units in Group R occupancies shall be provided with smoke alarms in accordance with Section 1103.8 of the California Fire Code .

503.15 Carbon monoxide alarms. [HCD 1] Pursuant to¶

Health and Safety Code Section 17926, carbon monoxide detection shall be provided in all existing Group R buildings, as required in Section 915 of the California Building Code or Section R315 of the California Residential Code, as applica- ble.

503.15.1 Carbon monoxide detection in alterations to an existing Group E building. Where the alteration adds any of the conditions identified in the California Fire Code Sections 915.1.2 through 915.1.6 to an existing Group E building, not previously required to be provided with car- bon monoxide detection, new carbon monoxide detection shall be installed in accordance with Section 915 of the California Fire Code.

Exceptions:

1. The alteration replaces an existing fossil-fuel burning appliance, fireplace, or forced-air fur- nace, or any of the conditions identified in Sec- tions 915.1.2 through 9151.6 are already present.

2. The Group E building was constructed before the adoption of the 2016 California Building Stan- dards Code.

503.16 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 that required in Sections 503.16.1 through 503.16.3.

503.16.1 Smoke compartments. In Group I-2 and I-3 occupancies, the required capacity of the refuge areas for smoke compartments in accordance with Sections 407.5.1

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stairways not less than 40 inches (1016 mm) wide by 36 inches (914 mm) long, located not more than 8 inches (203 mm) below the door.

[BE] 504.5 Opening protectives. Doors and windows within 10 feet (3048 mm) of fire escape stairways shall be protected with ³ /4-hour opening protectives.

Exception: Opening protection shall not be required in buildings equipped throughout with an approved automatic sprinkler system.