SPS 321.04 Stairways and elevated areas.
(a) General. Except as provided under par. (b), the following stairways shall conform to the requirements of this section. 1. Every interior and exterior stairway attached to, or supported by any part of the structure covered under this code. 2. Tub access stairs, unless they are an integral part of an approved plumbing product. (b) Exceptions. The following stairways are not required to comply with the requirements of this section:
1. Stairways leading to non-habitable attics or crawl spaces.
2. Non-required stairways connecting the basement directly to the exterior of the structure without communicating with any other part of the structure.
(2) Details. (a) Width.
1. Except for spiral staircases under subd. 2., stairways shall measure at least 36 inches in width. Handrails and associated trim may project a maximum of 4.5 inches into the required width at each side of the stairway. The minimum clear width at and below the handrail, including at treads and landings, may not be less than 31.5 inches where a handrail is installed on one side, and 27 inches where handrails are provided on both sides.
2. Spiral staircases shall be at least 26 inches wide measured from the outer edge of the supporting column to the inner edge of the handrail.
(b) Riser height. 1.a. Except for spiral staircases under subd. 2., risers may not exceed 8 inches in height measured vertically from tread to tread.
b. At the top and bottom of a flight, measurement shall be taken from the top of the nosing to the finished floor surface unless the finished surface is carpeting, in which case measurement shall be made to the hard surface below the carpeting.
2. Risers in spiral staircases may not exceed 9.5 inches in height measured vertically from tread to tread.
(c) Tread depth. 1. `Rectangular treads.' Rectangular treads shall have minimum tread depth of 9 inches measured horizontally from nosing to nosing.
2. `Spiral staircase treads.' Spiral staircase treads shall have a minimum tread depth of 7 inches from nosing to nosing measured at a point 12 inches from the outer edge of the center column.
3. `Winder treads in series.' Two or more winder treads may be placed immediately adjacent to each other anywhere in a stairway provided both of the following conditions are met:
a. The winder treads shall have a minimum tread depth of 7 inches measured at a point 12 inches from the narrow end of the tread.
b. The depth of the immediately adjoining winder treads shall be equal at a point 12 inches from the narrow end of the tread or inside face of spindles or balusters. c. Winder treads may not be used on a straight stairway.
4. `Individual winder treads.'
a. An individual winder tread may be placed between rectangular treads or at the end of a flight of rectangular treads provided the tread depth is at least 9 inches, when measured at a distance of 12 inches from the narrow end of the tread or from the inside face of the wall b. There may be more than one individual winder tread in a stairway. c. Winder treads may not be used on a straight stairway.
(d) Headroom. 1. Stairways shall be provided with a minimum headroom clearance of 76 inches measured vertically from a line parallel to the nosing of the treads to the ceiling, soffit or any overhead obstruction directly above that line.
2. The headroom clearance shall be maintained over an intermediate landing.
3. The headroom clearance shall be maintained over a landing that is at the top or bottom of a stairway for a minimum distance of 36 inches in the direction of travel of the stairway.
(e) Uniformity. 1. Within a stairway flight, the greatest tread depth may not exceed the smallest tread depth by more than 3/8 inch and the greatest riser height may not exceed the smallest riser height by more than 3/8 inch.
2. The allowed variation in uniformity under subd. 1. may not be used to exceed the maximum riser height under par. (b) or to decrease the minimum tread depth under par. (c). (f) Open risers. Stairways with open risers shall be constructed to prevent the through-passage of a sphere with a diameter of 4 inches or larger between any 2 adjacent treads. (g) Walking surface. The walking surface of stair treads and landings shall be a planar surface that is free of lips or protrusions that could present a tripping hazard. The horizontal offset between the 2 rails is no more than 12 inches measured from the center of the rails, and both the upper and lower rails can be reached from the same tread without taking a step.
(4) Landings. (a) Intermediate landings.
1. A level intermediate landing shall be provided in any stairway with a height of 12 feet or more.
2. Intermediate landings that connect 2 or more straight flights of stairs, or 2 flights of stairs at a right angle, shall be at least as wide as the treads and shall measure at least 36 inches in the direction of travel. 3. Curved or irregular landing shall have a radius of at least 36 inches.
4. Curved or irregular landings shall have a minimum straight line measurement of 26 inches between the nosing of the 2 connecting treads measured at a point 18 inches from the narrow end of the landing measured along the nosing of the 2 treads. (b) Landings at the top and base of stairs. A level landing shall be provided at the top and base of every stairs except as provided in par. (d). The landing shall be at least as wide as the treads and shall measure at least 3 feet in the direction of travel. (c) Doors at landings. Except as provided in subds. 1. to 3. and par. (d), level landings shall be provided on each side of any door located at the top or base of a stair, regardless of the direction of swing. In the following exceptions, a stairway between a dwelling and an attached garage, carport or porch is considered to be an interior stair:
1. A landing is not required between the door and the top of interior stairs if the door does not swing over the stairs.
2. A landing is not required between the door and the top of an interior stairs of 1 or 2 risers regardless of the direction of swing.
3. A landing is not required between a sliding glass door or an in-swinging glass door and the top of an exterior stairway of 3 or fewer risers.
(d) Exterior landings.
1. The exterior landing, platform, or sidewalk at an exterior doorway shall be located a maximum of 8 inches below the interior floor elevation, be sloped away from the doorway at a minimal rate that ensures drainage, and have a length of at least 36 inches in the direction of travel out of the dwelling.
2. The landing at the base of an exterior stair shall be sloped away from the stair at a minimal rate that ensures drainage.