(a)        Prior to the issuance of an alteration permit for the conversion of floor area to residential use, the Chairperson of the City Planning Commission shall certify compliance with the requirements of Section 15-21 upon proof of a legal commitment to preserve and maintain the required floor area for permitted commercial or permitted manufacturing use. Such legal commitment shall be executed by all parties having any interest in the floor area to be preserved as shown by a certificate issued by a title insurance company licensed to do business in the State of New York showing all such parties in interest.

A "party in interest" in the tract of land shall include only (W) the fee owner thereof, (X) the holder of any enforceable recorded interest superior to that of the fee owner and which could result in such holder obtaining possession of all or substantially all of such tract of land, (Y) the holder of any enforceable recorded interest in all or substantially all of such tract of land which would be adversely affected by the preservation as required herein, and (Z) the holder of any unrecorded interest in all or substantially all of such tract of land which would be superior to and adversely affected by the preservation required herein and which would be disclosed by a physical inspection of the tract of land.

A copy of the legal commitment required herein shall be recorded in the Conveyances Section of the Office of the City Register of New York County upon certification.

(b)        The floor area to be preserved shall not already have been preserved by a legal commitment under the provisions of Section 15-21, as evidenced by the report from the title company issued pursuant to (a) above.

(c)        When preservation obligations pursuant to Section 15-211 or 15-212 are transferred between buildings, the amount of floor area required to be preserved shall not be reduced by the existence of a previously issued legal commitment for preservation on a portion of the floor area in the building.

(d)        Any building that has been partially converted pursuant to Section 15-21 and has complied with the preservation requirements of such Section, shall not be required to preserve additional floor area for any subsequent conversion.