(a)        In buildings where floor area is converted to residences under Section 15-21 (Use Regulations — Transfer of Preservation Obligations and Conversion Rights) where there is more than one dwelling unit per story, there shall be a minimum dwelling unit size of 1,200 square feet of interior floor area unless modified pursuant to Section 15-30 (MINOR MODIFICATIONS).

However, the minimum dwelling unit size requirement may be replaced by the requirements of Section 15-026 for dwelling units existing on September 1, 1980:

(1)        for which the Chairperson of the City Planning Commission has made a determination of residential occupancy on September 1, 1980, pursuant to Section 15-021, paragraph (c) or Section 15-215; or

(2)        that are registered Interim Multiple Dwellings or are found covered by the New York City Loft Board pursuant to Article 7C of the New York State Multiple Dwelling Law; or

(3)        that the Loft Board determines were occupied for residential use on September 1, 1980.

Dwelling units existing on September 1, 1980 may not be subsequently divided into units of less than 1,200 square feet, unless required by the Loft Board for the legalization of Interim Multiple Dwelling Units in the implementation of Article 7C of the New York State Multiple Dwelling Law.

(b)        For the purposes of this Section only, mezzanines constructed pursuant to Chapter 26 of the Administrative Code shall be allowed within individual dwelling units provided that the gross area of such mezzanine does not exceed 33 and 1/3 percent of the floor area contained within such dwelling unit.  Such mezzanines are permitted only in buildings with an existing floor area ratio of 12 or less, and only between floors, or between a floor and a roof, existing on January 22, 1998, that are to remain. Such mezzanines shall not be included as floor area for the purpose of calculating the minimum required size of a dwelling unit or for calculating floor area devoted to dwelling units.