(a)        Street walls along Madison Avenue

For developments or enlarged portions of buildings with frontage on Madison Avenue or on a side street within 50 feet of its intersection with Madison Avenue, the following regulations shall apply:

(1)        The street wall of the base of such building shall be located on the street line or, if there is an existing abutting building fronting on the same street line that is set back from such street line, the street wall of the base may be aligned with the street wall of the abutting building for a distance of not less than 10 feet measured horizontally from the side wall of such abutting building. However, such setback distance shall not exceed 15 feet from the street line. All street walls built pursuant to this paragraph shall extend along the full length of the street line and rise vertically without setback for:

(i)        not less than 110 feet but not more than 120 feet above curb level ; or

(ii)        the full height of the building ;

whichever is less.

(2)        Above the base, a setback is required for all portions of a building which exceed a height of 120 feet above curb level. Such setback shall be provided at a height not lower than 110 feet above curb level, and shall have a minimum depth of 10 feet from a wide street line and a minimum depth of 15 feet from a narrow street line.

(3)        No portion of a building may exceed the height limitations of Section 99-054 (Maximum building height).

(b)        Street walls along side streets

For developments or enlarged portions of buildings with frontage on a side street beyond 50 feet of its intersection with Madison Avenue, the following regulations shall apply:

(1)        The street wall of the base of such building shall be located on the street line or, if there is an existing abutting building fronting on the same street line that is set back from such street line, the street wall of the base shall be aligned with the street wall of the abutting building for a distance of not less than 10 feet measured horizontally from the side wall of such abutting building. However, such setback distance need not exceed 10 feet from the street line. All street walls built pursuant to this paragraph shall extend along the full length of the street line and rise vertically without setback for:

(i)        a height of 60 feet above curb level ; or

(ii)        the height of a street wall before setback, if applicable, of that portion of an existing building nearest the development or enlargement, fronting on the same street line, and located on the same or an adjoining zoning lot ;

whichever is higher.

(2)        Alternatively, the street wall location provisions of paragraph (a) of this Section may apply to the base of a building along a side street beyond 50 feet of its intersection with Madison Avenue, up to a distance of 70 feet from its intersection with Madison Avenue.

(3)        Above the base, a setback is required for all portions of a building. Such setback shall have a minimum depth of 10 feet from a wide street line and a minimum depth of 15 feet from a narrow street line.

(4)        No portion of a building may exceed the height limitations of Section 99-054 (Maximum building height).

(c)        Street walls in Historic Districts

For any zoning lot located in a Historic District designated by the Landmarks Preservation Commission, the minimum base height and street wall location regulations of this Section shall be modified as follows:

(1)        The minimum base height of a street wall may vary between the height of the street wall of an adjacent building before setback, if such height is lower than the minimum base height required, up to the minimum base height requirements of this Section.

(2)        The location of the street wall of any building may vary between the street wall location requirements of this Section, and the location of the street wall of an adjacent building fronting on the same street line.