The city's seismic ordinance classifies the various building code occupancies into five "relative hazard" levels. Locating an A2 assembly occupancy in most locations would require that the entire building be seismically upgraded, since the seismic regulations classify an assembly occupancy at the highest hazard level. Most potential locations, such as in buildings that were constructed to be used for retail, storage or manufacturing, will have the legal occupancy grandfathered at a lower hazard level. When the change in use is to a higher relative hazard occupancy, you are generally required to upgrade the entire building if more than 1/3rd of the area of the building is changed, or if the change results in an increase of more than 149 occupants.
The triggers for seismic (area and occupant load) are cumulative over time, so if a portion of the building has already been changed without requiring an upgrade, your proposed project may cross over the allowed thresholds, so it is important to research the history of the building.
For more information on seismic triggers and your project, call a Life Safety Reviewer at (503) 823-1456.