Los Angeles Municipal Code Div. 5 Prescriptive Compliance Method

(Title Amended by Ord. No. 188,797, Eff. 12/31/25.)

Section

• 91.2.500 Basic Provisions.

• 91.2.501 General.

• 91.2.502 Additions.

• 91.2.503 Alterations.

• 91.2.506 Change of Occupancy.

(Amended by Ord. No. 188,797, Eff. 12/31/25.)

Chapter 5 of the CEBC is hereby adopted by reference except as amended herein.

(Added by Ord. No. 188,797, Eff. 12/31/25.)

Section 501 of the CEBC is hereby adopted by reference except as amended herein.

91.2.501.1. Scope. The provisions of this division shall control the alternation, addition and change of occupancy of existing buildings and structures, including historic buildings and structures, [BSC] including state-regulated structures in accordance with Section 501.1.2 of the CEBC. Historic buildings and structures shall comply with Part 8, Title 24, C.C.R. In addition to the requirements of the CEBC, existing buildings and structures shall comply with the applicable regulations of Divisions 81, 82, 83, 84, 85, 86, 88, 89, 91, 93, 95 and 97 of the Los Angeles Building Code (LABC), Article 1, Chapter IX of the LAMC, Appendix A Chapters A1, A2, A3, A4 and A5 of the LAEBC, and the voluntary earthquake hazard reduction standards of Divisions 92, 94 and 96 of Article 1, Chapter IX of the LAMC.

91.2.501.6. Unreinforced Masonry Buildings. For unreinforced masonry (URM) buildings with an approved occupant load greater than 100, the occupant load may be increased by a maximum of 10 percent as long as the Rating Class or Risk Category is not changed.

If the occupant load increase is over 10 percent, then compliance with CEBC Appendix Chapter A1 is required as long as there is no change in Risk Category. If there is a change in Risk Category, then compliance with CEBC Section 304.3.1 is required.

(Added by Ord. No. 188,797, Eff. 12/31/25.)

Section 502 of the CEBC is hereby adopted by reference except as amended herein.

91.2.502.4. 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 lateral force-resisting system of the existing structure and its addition acting together as a single structure shall comply with Section 1609 of the California Building Code and with Section 304.3.1 of this code.

EXCEPTIONS:

1. Except for Unreinforced Masonry (URM) Buildings, any existing lateral load-carrying structural element whose demand-capacity ratio with the addition considered is not 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 and 1613 of the California Building 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. When calculating demand-capacity ratios for wind, the date of original construction shall be permitted to be taken as the date of completion of a prior addition, alteration or repair in compliance with Section 1609 of the California Building Code or the code wind forces in effect at the time. When calculating demand-capacity ratios for earthquake, the date of original construction shall be permitted to be taken as the date of completion of a prior addition, alteration or repair in compliance with CEBC Section 304.3.1 or the full seismic forces in effect at the time.

The additions do not create structural irregularity as defined in ASCE 7 or make an existing structural irregularity more severe.

2. For Unreinforced Masonry (URM) Buildings, any existing lateral load-carrying structural element whose demand-capacity ratio with the addition considered is less than 10 percent greater than its demand-capacity ratio with the addition ignored, must comply with CEBC Appendix Chapter A1. Any existing lateral load-carrying structural element whose demand-capacity ratio with the addition considered is 10 percent or greater than its demand-capacity ratio with the addition ignored, must comply with CEBC Section 304.3.1.

3. Buildings of Group R occupancy with not more than five dwelling or sleeping units used solely for residential purposes where the existing building and the addition together comply with the conventional light-frame construction methods of the California Building Code or the provisions of the California Residential Code.

(Added by Ord. No. 188,797, Eff. 12/31/25.)

Section 503 of the CEBC is hereby adopted by reference except as amended herein.

91.2.503.4. Existing Structural Elements Carrying Lateral Load. Except as permitted by CEBC 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 lateral force-resisting system of the altered building or structure shall meet the requirements of Section 1609 of the California Building Code and Section 304.3.2 of this code. Reduced seismic loads, in accordance with CEBC Section 304.3.2, shall be permitted provided the reduced seismic load is not less than the original building permitted seismic loads.

EXCEPTIONS:

1. Except for Unreinforced Masonry Buildings (URM), 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 Section 1609 of the California Building Code and Section 304.3.1 or 304.3.2 of this code. The same methodology shall be used for the altered and unaltered structures. 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. When calculating demand-capacity ratios for wind, the date of original construction shall be permitted to be taken as the date of completion of a prior addition, alteration or repair in compliance with Section 1609 of the California Building Code or the code wind forces in effect at the time. When calculating demand-capacity ratios for earthquake, the date of original construction shall be permitted to be taken as the date of completion of a prior addition, alteration or repair in compliance with CEBC Section 304.3.1 or CEBC Section 304.3.2, Item 1 or 3, or the full or reduced seismic forces in effect at the time. Reduced seismic loads, in accordance with CEBC Section 304.3.2, shall be permitted provided the reduced seismic load is not less than the original building permitted seismic loads.

The alternations do not create structural irregularity as defined in ASCE 7 or make an existing structural irregularity more severe.

2. For Unreinforced Masonry (URM) Buildings, any existing lateral load-carrying structural element whose demand-capacity ratio with the alteration considered is less than 10 percent greater than its demand-capacity ratio with the alteration ignored, must comply with CEBC Appendix Chapter A1. Any existing lateral load-carrying structural element whose demand-capacity ratio with the alteration considered is 10 percent or greater than its demand-capacity ratio with the alteration ignored, must comply with CEBC Section 304.3.1.

Structural analysis per CEBC Appendix Chapter A1 is required for any alterations to crosswalls or diaphragms.

3. Except for Unreinforced Masonry Buildings (URM), buildings in which the increase in the demand-capacity ratio is due entirely to the addition of rooftop-supported mechanical equipment individually having an operating weight less than 400 pounds (181.4 kg) and where the total additional weight of all rooftop equipment placed after initial construction of the building is less than 10 percent of the roof dead load. For purposes of this exception, “roof” shall mean the roof level above a particular story.

4. Except for Unreinforced Masonry Buildings (URM), increases in the demand-capacity ratio due to lateral loads from seismic forces need not be evaluated for the installation of rooftop photovoltaic panel systems where the additional roof dead load due to the system, including ballast where applicable, does not exceed 5 pounds per square foot (psf) (0.2394 kN/m 2 ) and does not exceed 10 percent of the dead load of the existing roof.

(Added by Ord. No. 188,797, Eff. 12/31/25.)

Section 506 of the CEBC is hereby adopted by reference except as amended herein.

91.2.506.5.3. Seismic Loads (seismic force-resisting system). Where a change of occupancy results in a building being assigned to a higher Risk Category, or where the change is from a Group S or U occupancy to an occupancy other than Group S or Group U, the lateral force-resisting system of the building shall comply with CEBC Section 304.3.1 for the new Risk Category. Where a change of occupancy results in a building being assigned to Risk Category IV and Seismic Design Category D or F, nonstructural components serving any portion of the building changed to Risk Category IV shall comply with the requirements of Section 1613 of the California Building Code or shall comply with ASCE 41 using an objective of Operational nonstructural performance with the BSE-1N earthquake hazard level.

EXCEPTIONS:

1. Where the area of the new occupancy is less than 10 percent of the building area, the occupancy is not changing from a Group S or Group U, and the new occupancy is not assigned to Risk Category IV, compliance with this Section is not required. The cumulative effect of occupancy changes over time shall be considered.

2. Where a change of use results in a building being reclassified from Risk Category I or II to Risk Category III and the seismic coefficient, SDS, is less than 0.33, compliance with this section is not required.

3. Unreinforced masonry bearing wall buildings assigned to Risk Category III and to Seismic Design Category A or B shall be permitted to use Appendix Chapter A1 of this code.

4. Where the change is from a Group S or Group U occupancy and there is no change of Risk Category, compliance with CEBC Section 304.3.2 shall be permitted. Reduced seismic loads, in accordance with CEBC Section 304.3.2, shall be permitted provided the reduced seismic load is not less than the original building permitted seismic loads.

For a change of occupancy of an existing commercial or industrial building to residential use, all existing buildings shall be analyzed for 75 percent of the design earthquake ground motion, as defined in CBC Section 1613, but in no event shall there be a reduction in the capacity of the seismic force resisting system where that system provides a greater level of protection than the minimum requirements established by this Code.

For an existing URM building, structural analysis per CBC Chapter 16 is required if the Risk Category is changed to III or IV. Structural analysis per CEBC Appendix A1 is required if rating classification per LABC Division 88, Table 88-A is changed to I or II. The most restrictive requirements of CEBC Sections 502 (Addition), 503 (Alternation), 405 (Repair) and 506 (Change of Occupancy) shall apply.