CBC Table 1604.5 assigns Risk Category IV to essential facilities (hospitals, EOCs, fire stations) and any building over 240 ft with mixed-use. Effects: importance factor I_e = 1.5 for seismic, 1.15 for wind; mandatory base-isolation or moment-frame ductility for tall structures in SDC D+; continuous-operation drift limit of 0.010 h_sx vs 0.020 for Cat II; independent peer review by SE required per §1604.6 in California. SF DBI additionally requires SETC review for any project above 160 ft.