§ 240. First tier of beams. 1. In all tenements erected after April twelfth, nineteen hundred one, which are five stories or more in height, the first floor above the lowest cellar, or, if there be no cellar, above the basement or other lowest story, shall be fireproof; and all exposed portions of any iron or steel beams below the floor arches shall be fire-retarded.

2. In all non-fireproof tenements erected after such date which are four stories or less in height, the ceiling of the lowest cellar, or, if there be no cellar, of the basement or other lowest story, shall be fire-retarded or covered with plaster boards at least one-half inch in thickness, with all joints made true and well pointed.

3. In all old-law tenements which are four stories or more in height the ceiling of the cellar, or, if there be no cellar, of the basement or other lowest story, shall be fire-retarded.