Los Angeles Municipal Code Div. 11 Additions

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

Section

91.2.1100 Basic Provisions.

91.2.1103 Structural.

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

Chapter 11 of the CEBC is hereby adopted by reference except as amended herein.

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

Section 1103 of the CEBC is hereby adopted by reference except as amended herein.

91.2.1103.2. Lateral force-resisting system. 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. 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.

2. 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 of the California Building Code and Section 304.3.1 of this 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.

3. 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.