(a)        Height of street walls

        The street wall of any building shall be located on the street line and extend along the entire street frontage of the zoning lot not occupied by existing buildings to remain. Such street wall shall rise without setback to a minimum base height of 80 feet and a maximum base height of 90 feet before setback. However, if the height of an adjacent street wall fronting on the same street line is higher than 90 feet before setback, the street wall of the new or enlarged building may rise without setback to the height of such adjacent street wall, up to a maximum height of 120 feet.

        For zoning lots, or portions thereof, with street frontage of 25 feet or less and existing on June 29, 2010, a minimum base height lower than 80 feet shall be permitted along such street frontage in accordance with the following provisions:

(1)        where the height of an adjacent street wall fronting on the same street line is at least 60 feet and less than 80 feet, the street wall of the new or enlarged building may rise without setback to the height of such adjacent street wall; or

(2)        where the height of an adjacent street wall fronting on the same street line is less than 60 feet, the street wall of the new or enlarged building may rise without setback to a minimum street wall height of 60 feet.

        The street wall of any building may rise to a height less than the minimum base height required pursuant to this paragraph (a), provided that no building on the zoning lot exceeds such height, except where such building is located on a zoning lot with multiple buildings, one or more of which is developed, enlarged or altered after February 2, 2011, to a height exceeding the minimum base height required pursuant to this paragraph (a).

(b)        Maximum building height

        Above a height of 90 feet or the height of the adjacent street wall if higher than 90 feet, no portion of a building or other structure shall penetrate a sky exposure plane that begins at a height of 90 feet above the street line, or the height of the adjacent street wall if higher than 90 feet, and rises over the zoning lot at a slope of four feet of vertical distance for each foot of horizontal distance to a maximum height limit of 250 feet, except as provided below:

(1)        any portion of the building or other structure developed or enlarged pursuant to the tower regulations of Sections 33-45 (Tower Regulations) or 35-64 (Special Tower Regulations for Mixed Buildings), as applicable, may penetrate the sky exposure plane, provided no portion of such building or other structure exceeds the height limit of 250 feet; and

(2)        permitted obstructions, as listed in Section 33-42, may penetrate the sky exposure plane and the height limit of 250 feet. In addition, a dormer, as listed in paragraph (c)(1) of Section 23-623 (Permitted obstructions in certain districts), may penetrate the sky exposure plane.

        On a zoning lot with frontage of at least 200 feet along at least one street, up to 20 percent of the aggregate width of the street wall facing such street, for a maximum width of 50 feet, may be recessed to a maximum depth of 15 feet from the street line, provided the recessed area is located a minimum of 20 feet from an adjacent building and that a minimum of 60 percent of such area is planted with any combination of grass, ground cover, shrubs, trees or other living plant material in the ground or in planters permanently affixed to the ground.