301A.3 Alteration, Addition or Change of Occupancy
The alteration, addition or change of occupancy of all existing buildings or structures shall comply with one of the methods or categories listed in Section 301A.3.1, 301A.3.2 or 301A.3.3 Section 303A.3.2 applies to all methods or categories. Sections 301A.3.1 through 301A.3.3 shall not be applied in combination with each other, except when permitted by the enforcement agency.
Exception: Subject to the approval of the enforcement agency, alterations complying with the laws in existence at the time the building or the affected portion of the building was built shall be considered in compliance with the provisions of this code. New structural members added as part of the alteration shall comply with the California Building Code.