SEC. 91.2.500. BASIC PROVISIONS. Chapter 5 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, [BSC] including state-regulated structures in accordance with Section 501.1.2 of the CEBC. 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) at Article 1, Chapter IX of the LAMC, Appendix A Chapters A1 and A2 of the LAEBC, and the voluntary earthquake hazard reduction standards of Divisions 92, 94 and 96 of Article 1, Chapter IX of the LAMC. 91.2.502.5. Existing Structural Elements Carrying Lateral Load. (Amended by Ord. No. 188,739, Eff. 9/23/25.) 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 existing structure and its addition acting together as a single structure shall be shown to meet the requirements of Sections 1609 and 1613 of the California Building Code using full seismic forces. For purposes of CEBC Section 502, compliance with ASCE 41, using a Tier 3 procedure and the two-level performance objective in CEBC Table 304.3.1 for the applicable risk category, shall be deemed to meet the requirements of CBC Section 1613, with procedures established by the Department. EXCEPTIONS: 1. Except for Unreinforced Masonry (URM) Buildings: Any existing lateral load-carrying structural element whose demand-capacity ratio with the addition considered is no more than 10% 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 CBC Sections 1609 and 1613. For purposes of this exception, comparisons of demand-capacity ratios and calculations of design lateral loads, forces and capacities shall account for the cumulative effects of additions and alterations since original construction.