N.Y. Multiple Dwelling Law § 150: Cellar and basement stairs

§ 150. Cellar and basement stairs. 1. Except as otherwise provided in

this section, there shall be no inside stair communicating between the

lowest cellar or the lowest story, if there be no cellar, and the floor

next above, but any stair communicating between such floors shall be

located outside the dwelling and if enclosed shall be fireproof in a

fireproof enclosure with fireproof doors and door assemblies, with the

doors self-closing, at all openings.

2. This provision, however, shall not apply to any stair not extending

through more than one story and leading from an entrance hall to the

upper stories where the walls enclosing such hall are fireproof and

unpierced except for openings to stairs, elevators, apartments, public

reception rooms, professional offices and the outer air. In no event

shall there be any other opening from such an entrance hall, and all

apartments and such professional offices opening therefrom shall be

entirely separated from any space within such dwelling used for any

other purposes by fireproof walls which shall be unpierced except for

means of egress into the entrance hall. The provisions of this

subdivision shall not apply to openings which are protected with

fireproof vestibules. Any such vestibule shall have a minimum

superficial floor area of fifty square feet and its maximum area shall

not exceed seventy-five square feet. It shall be enclosed with

incombustible partitions having a fire-resistive rating of three hours.

The floor and ceiling of such vestibule shall also be of incombustible

material having a fire-resistive rating of at least three hours. There

shall be two doors to provide access from the entrance hall and any

other space not used for openings to stairs, elevators, apartments,

public reception rooms and the outer air. Each such door shall have a

fire-resistive rating of one and one-half hours and shall be provided

with a device to prevent the opening of one door until the other door is

entirely closed. One of these doors shall swing into the vestibule from

the entrance hall and the other shall swing from the vestibule into

space which it serves. Such vestibule shall also be equipped with

sprinklers and with an independent exhaust duct having a minimum

cross-sectional area of one hundred forty-four square inches for each

one thousand cubic feet, or fraction thereof, of air content, and such

exhaust duct shall not be connected with any other ventilating system.

3. In dwellings three stories or less in height which are occupied by

two families or less on every story, any stair leading to the cellar may

be located inside the dwelling provided it is entirely enclosed with

fireproof walls and with fireproof doors and door assemblies at both the

cellar level and the story above, with the doors self-closing.

4. The provisions of subdivision one shall not prohibit or apply to an

inside stair extending from a space used for commercial purposes in the

cellar or lowest story to a store on the story next above, provided such

stair is of incombustible materials, has closed risers, is enclosed

between the two lowest floors with walls having a three-hour fire

resistive rating and has fireproof doors and door assemblies at top and

bottom, with the doors self-closing, and provided such commercial space

in the cellar or lowest story is completely enclosed with partitions

having a fire-resistive rating of at least two hours and there is no

opening between the store on the story next above and any entrance hall

or other public hall or public portion of the dwelling.