In Commercial Districts, the underlying height and setback provisions are modified as follows:

1. Basic Height and Setback Regulations
   
   In Commercial Districts, the maximum height of buildings or other structures shall be as set forth in Section 35-632 (Maximum height of buildings and setback regulations), as applicable, except that:
   1. the minimum base heights shall be modified by the provisions of Section 138-22 (Street Wall Regulations);
   2. in C2 Districts mapped within an R9 District that is also located within 100 feet of Third Avenue, the maximum building height for buildings utilizing the provisions of paragraph (b) of Section 35-632 shall be modified to 215 feet;
   3. in C4-6 Districts whose maximum residential floor area ratio is 9.0, as set forth on Map 2 of the Appendix to this Chapter, the applicable provisions of paragraphs (a) or (b) of Section 35-632 for R9 Districts shall apply, except that the minimum base height set forth in Section 138-22 shall apply, the maximum building height for buildings utilizing the provisions of paragraphs (b) of Section 35-632 shall be modified to 215 feet;
   4. in a C2 District mapped within an R7D District that is also located within 100 feet of Park Avenue, the maximum building height for buildings utilizing the provisions of paragraph (b) of Section 35-632 shall be modified to 125 feet; and
   5. where applicable, in lieu of the provisions of this paragraph, the provisions of paragraph (b) of this Section may be applied.
2. Alternate Height and Setback Regulations in Certain Districts
   
   In C2 Districts mapped within an R9 or R10 District, or in C4-6 or C6-4 Districts, as an alternative to the provisions of paragraph (a) of this Section, the provisions of this paragraph may be applied to zoning lots providing qualifying affordable housing or qualifying senior housing, or to zoning lots where 50 percent or more of the floor area is occupied by non-residential uses.
   1. Setbacks
      
      At a height not lower than the minimum base height specified in Section 138-22 (Street Wall Regulations), nor higher than a maximum base height of 85 feet, a setback shall be provided in accordance with Section 23-433 (Standard setback regulations). Above such required setback, any portion of such building shall be considered a “tower.”
   2. Lot coverage requirements for towers
      
      Each story of a tower shall not exceed a maximum lot coverage of 50 percent. However, where dormers are provided within the required setback, such portions of buildings shall not count toward the maximum allowable tower lot coverage set forth in this paragraph.
   3. Maximum tower height
      1. The maximum tower height shall be set forth on Map 3 of the Appendix to this Chapter.
      2. In C2 Districts mapped within R9 Districts that are also located within the Special Transit Land Use District, for zoning lots which include a transit easement in accordance with the applicable provisions of Article IX, Chapter 5 (Special Transit Land Use District), the maximum tower height shall be:
         1. 325 feet for zoning lots which include ancillary facilities with emergency egress and/or ventilation structures as specified in Section 95-032 (Determination of transit easement at other stations); and
         2. 215 feet for zoning lots which include only transit facilities specified in Section 95-032 other than ancillary facilities with emergency egress and/or ventilation structures.