506.4.3 Seismic Loads (Seismic Force-Resisting System)
Where a change of occupancy results in a building being assigned to a higher risk category, the building shall satisfy the requirements of Section 1613 of the International Building Code for the new risk category using full seismic forces.
- Where the area of the new occupancy is less than 10 percent of the building area and the new occupancy is not assigned to Risk Category IV, compliance with this section is not required. The cumulative effect of occupancy changes over time shall be considered.
- Where a change of use results in a building being reclassified from Risk Category I or II to Risk Category III and the seismic coefficient, SDS, is less than 0.33, compliance with this section is not required.
- Unreinforced masonry bearing wall buildings assigned to Risk Category III and to Seismic Design Category A or B, shall be permitted to use Appendix Chapter A1 of this code.