Cal. Health & Safety Code § 18941.6

(a) Notwithstanding any other provision of this part, ordinances and programs adopted on or before January 1, 1993, that contain standards to strengthen potentially hazardous buildings pursuant to subdivision (b) of Section 8875.2 of the Government Code, shall incorporate the building standards in Appendix Chapter 1 of the Uniform Code for Building Conservation of the International Conference of Building Officials published in the California Building Standards Code, except for standards found by local ordinance to be inapplicable based on local conditions, as defined in subdivision (b), or based on an approved study pursuant to subdivision (c), or both. Ordinances and programs shall be updated in a timely manner to reflect changes in the model code, and more frequently if deemed necessary by local jurisdictions.
(b) For the purpose of subdivision (a), and notwithstanding the meaning of “local conditions” as used elsewhere in this part and Part 2.5 (commencing with Section 18901), the term “local conditions” shall be limited to those conditions that affect the implementation of seismic strengthening standards on the following only:
1. (1) The preservation of qualified historic structures as governed by the State Historical Building Code (Part 2.7 (commencing with Section 18950)).
2. (2) Historic preservation programs, including, but not limited to, the California Mainstreet Program.
3. (3) The preservation of affordable housing.
(c) Any ordinance or program adopted on or before January 1, 1993, may include exceptions for local conditions not defined in subdivision (b) if the jurisdiction has approved a study on or before January 1, 1993, describing the effects of the exceptions. The study shall include a seismic hazards assessment, seismic retrofit cost comparisons, and earthquake damage estimates for a major earthquake, including the differences in costs, deaths, and injuries between full compliance with Appendix Chapter 1 of the Uniform Code for Building Conservation and the ordinance or program. No study shall be required pursuant to this subdivision if the exceptions for local conditions not defined in subdivision (b) result in standards or requirements that are more stringent than those in Appendix Chapter 1 of the Uniform Code for Building Conservation.
(d) Ordinances and programs adopted pursuant to this section shall be conclusively presumed to comply with the requirements of Chapter 173 of the Statutes of 1991.