a. Cellar occupancy: No room in the cellar of a one- or two-family dwelling shall be rented and no member of the family or families occupying the dwelling shall use such room for sleeping, eating or cooking purposes, except that a secondary kitchen for accessory cooking may be located in the cellar.
b. Use of basement by occupants of the dwelling: A room in the basement of a one- or two-family dwelling may be occupied for living purposes by members of the family or families in conjunction with their occupancy of the dwelling if the following conditions are met:
(1) Such room complies with all of the requirements of this code for rooms which are not located in the cellar or basement; except that the minimum ceiling height required in one family dwellings shall be seven feet.
(2) Whenever the department determines that the subsoil conditions on the lot so require, the basement or other lowest floor and all exterior walls as high as the ground level shall be dampproofed and waterproofed.
c. Rental of basement: An apartment, in the basement of a one-family dwelling may be occupied, unless otherwise prohibited under the zoning resolution of the city of New York, if it meets the requirements of subdivision b and all of the following conditions:
(1) Such basement occupancy is limited to one family which, for the purposes of this section, shall not include boarders.
(2) Every room shall have a window complying with the requirements of section 27-2062 of article one of this subchapter.
(3) The bottom of any yard or other required open space shall be no higher than six inches below the window sill of any required window in any room.
d. Conversion to multiple dwelling. No private dwelling of more than three stories in height which was erected after April eighteenth, nineteen hundred twenty-nine shall be converted to a multiple dwelling unless it complies with all the provisions of the multiple dwelling law applicable to dwellings erected after April eighteenth, nineteen hundred twenty-nine.