The building structure and seismic resistance of an egress path through, under or over an existing building must meet the required seismic improvement standard specified in Section 24.85.040, Table 24.85-A, under any of the following conditions:

1. A. The egress path is from an adjacent new building or addition and the new building or addition area equals 1/3 or more of the existing building area; or,
2. B. The egress path is from an adjacent existing building that undergoes alterations or a change of occupancy requiring its egress path(s) meet the seismic improvement standards as required by this Chapter; or
3. C. The additional occupant load, as determined by the OSSC, using the egress path through the existing building is 150 people or more.