Chapter 34 of the California Building Code addresses the issue of when code upgrades are triggered in existing buildings.
Section 3401 states, "Buildings in existence at the time of the adoption of this code may have their existing use continued, if such use or occupancy was legal at the time of the adoption of this code, provided such continuous use is not dangerous to life".
Section 3403 deals with additions, alterations and repairs of existing buildings in that "Additions, alterations or repairs may be made to any building or structure without requiring the existing building or structure to comply with all the requirements of this code, provided the addition, alteration or repair conforms to that required for a new building or structure".
The basic premise of Chapter 34 is that if you touch it you need to bring it up to current code. If there is no work then there is no requirement to upgrade.
Issued February 21, 2006
Public Works Department