§ 52. Stairs. 1. In every multiple dwelling erected after April
eighteenth, nineteen hundred twenty-nine, every interior stair,
fire-stair and fire-tower and every exterior stair in connection with
any dwelling altered or erected after January first, nineteen hundred
fifty-one, shall be provided with proper balustrades or railings and all
such interior and exterior stairs shall be kept in good repair and free
from any encumbrance. Every such stair, fire-stair and fire-tower more
than three feet eight inches wide shall be provided with a handrail on
each side.

2. The upper surface of every balustrade or railing placed in any
stair after April eighteenth, nineteen hundred twenty-nine, shall be at
least two feet six inches and at most two feet eight inches above the
front edge of the stair treads, and at any stair landing shall be at
least two feet eight inches and at most three feet above the level of
such landing.

3. The treads and risers of every stair, fire-stair and fire-tower
constructed after April eighteenth, nineteen hundred twenty-nine, in any
multiple dwelling shall be of uniform height and width in any one
flight. Each tread, exclusive of nosing, shall be not less than nine and
one-half inches wide; each riser shall not exceed seven and
three-quarters inches in height; and the product of the number of inches
in the width of the tread and the number of inches in the height of the
riser shall be at least seventy and at most seventy-five.

4. No winding stairs shall be constructed in any multiple dwelling.

5. a. Except as otherwise provided in paragraph b of this subdivision,
every stair constructed after April eighteenth, nineteen hundred
twenty-nine, leading to a cellar or basement from the first story above
shall be entirely enclosed with fireproof walls and be provided with
fireproof doors and assemblies at both top and bottom, with the doors
self-closing; except that, in a non-fireproof multiple dwelling erected
before such date, where such a stair is permitted such enclosing walls
may be fire-retarded.

b. When the first floor or a part thereof, in a fireproof multiple
dwelling, is used for business purposes, a stair leading to a cellar or
basement from such business space shall be enclosed in fireproof walls
having a fire-resistive rating of at least three hours and be provided
with a fireproof door and assembly at the bottom, with the door
self-closing. No opening shall be permitted between such business space
and the remainder of the dwelling.

6. The department shall have the power to make supplementary
regulations relating to fire-towers.

7. In every multiple dwelling erected under plans filed with the
department after January first, nineteen hundred sixty, on every story
above the entrance story every door opening into such stair shall be so
hung and arranged that in opening and when opened it shall at no point
reduce the clear and unobstructed required width of the stair or stair
landing.

8. The provisions of this section shall not apply to a stair within an
apartment provided that each level of the apartment is provided with
required means of egress complying with the provisions of this article.