§ 143. Construction of first floor. 1. The first floor above the lowest cellar, or, if there be no cellar, above the lowest story, shall be fireproof or, if the dwelling be three stories or less in height, fire-retarded. Said first floor shall be unpierced except for a stair leading to a cellar as provided in section one hundred fifty, for lawful pipes, conduits and ducts and for dumbwaiter and elevator shafts. Any such dumbwaiter and elevator shafts shall be equipped at all openings below the said first floor with fireproof doors and assemblies with the doors self-closing.

2. Whenever the lowest cellar does not extend over more than half the area of the dwelling, that portion of the first floor directly over such cellar and the entire second floor above such cellar shall be constructed as in this section prescribed for the first floor above the lowest cellar. Whenever the lowest cellar extends over more than half, but not all, of the area of the dwelling, only that portion of the first floor directly over such cellar need be constructed as in this section prescribed for the first floor above the lowest cellar.