§ 242. Cellar and basement stairs in non-fireproof tenements. 1. Cellar stairs in non-fireproof tenements erected after April twelfth, nineteen hundred one, which are occupied by three families or more on any story or which are five stories or more in height, shall be governed by the provisions of section one hundred fifty for non-fireproof multiple dwellings erected after April eighteenth, nineteen hundred twenty-nine. In all other non-fireproof tenements erected after April twelfth, nineteen hundred one, any stair leading to a cellar may be located inside the building, provided it is enclosed with fireproof walls and is provided with fireproof doors and assemblies at both the top and bottom, with the doors self-closing.

2. In old-law tenements exceeding a basement and three other stories in height and provided with an inside cellar stair communicating between the entrance story and a cellar or lower story, the opening to such stair if located underneath the main stair leading to the upper stories shall be enclosed from the level of the entrance story up to the underside of the first flight of such main stairs. The soffit of such first flight of main stairs and the partitions forming such enclosure shall be fire-retarded or covered with twenty-six gauge metal. The opening to such enclosure shall be provided with a fireproof door and assembly with the door self-closing.