(a) Rise; Run. No step of any stairway in a dwelling shall have a rise of more than eight inches, nor a run of less than nine inches.
(b) Width and Handrails for Particular Dwellings. Stairways for dwellings of Divisions (b), (c) and (d) shall not be less than three feet wide in the clear. The open side of all landings and stairs of more than three risers shall be provided with handrails. Stairways which are enclosed on both sides shall be provided with handrails on at least one side.
(c) Partitions. Stairways for dwellings of Divisions (c) and (d) shall be enclosed in partitions made either of masonry or wood studs, plastered over a fireproof base.
(d) Soffits. The soffits of stairways in dwellings of Divisions (c) and (d) shall be plastered on metal lath or a fireproof base.
(e) Number Required. Two stairways shall be provided in all dwellings of Divisions (c) and (d).
(f) Winders. No stairways of dwellings of Divisions (b), (c) and (d) shall have winders.
(g) Landings. The landing of stairways in dwellings of Divisions (b), (c) and (d) shall be level.
(h) Number of Risers. No flight of any stairs in dwellings of Divisions (b), (c) and (d) shall have more than twenty risers.
(i) Head Room in Particular Dwellings. The head room for all stairways in dwellings of Divisions (b), (c) and (d) shall not be less than seven feet.
(j) Width and Stairways Generally. Stairways shall not be less than thirty-six inches in clear width at all points above the permitted handrail height and below the required headroom height. The minimum width at and below the handrail height shall not be less than thirty-two inches where a handrail is installed on one side and twenty-eight inches where handrails are provided on both sides.
(k) Treads and Risers. The maximum riser height shall be eight inches and the minimum tread depth shall be nine inches. The riser height shall be measured vertically between leading edges of the adjacent treads. The tread depth shall be measured horizontally between the vertical plans of the foremost projection of adjacent treads and at a right angle to the tread's leading edge. The walking surface of treads and landings of a stairway shall be sloped not steeper than one unit vertical and forty-eight units horizontal (two percent slope). The greatest riser height within any flight of stairs shall not exceed the smallest by more than three-eights of an inch. The greatest tread depth within any flight of stairs shall not exceed the smallest by more than three-eights of an inch.
(l) Profile. The radius of curvature at the leading edge of the tread shall be no greater than nine-sixteenths of an inch. A nosing not less than three-quarters of an inch but not more than one and one-quarter inches shall be provided on stairways with solid risers. Beveling of nosing shall not exceed one-half of an inch. Risers shall be vertical or sloped from the underside of the leading edge of the tread above at an angle not more than thirty degrees from the vertical. Exception: A nosing is not required where the tread depth is a minimum of eleven inches.
(m) Head Room Generally. The minimum headroom in all parts of the stairway shall not be less than six feet eight inches measured vertically from the sloped plan adjoining the tread nosing or from the floor surface of the landing or platform.
(n) Winders. Winders are permitted, provided that the width of the tread at a point not more than twelve inches from the side where the treads are narrower is not less than nine inches and the minimum width of any tread is not less than six inches. The continuous handrail required by subsection (j) hereof shall be located on either side of the stair.
(o) Spiral Stairs. Spiral stairways are permitted, provided the minimum width shall be twenty-six inches with each tread having a seven and one-half inch minimum tread width at twelve inches from the narrow edge. All treads shall be identical and the rise shall be no more than nine and one-half inches. A minimum headroom of six feet six inches shall be provided.
(p) Circular Stairways. Circular stairways shall have a minimum tread depth and a maximum riser height in accordance with subsection (l) and the smaller radius shall not be less than twice the width of the stairway. The minimum tread depth of nine inches shall be measured from the narrower end.
(Ord. 1177. Passed 3-3-30; Ord. 196-64. Passed 9-8-64; Ord. 165-98. Passed 5-18-98.)