California Building Codes Regarding Stairways
The following is provided for reference only, is believed to be accurate but no guarantee is expressed or implied. Please see the California State website for current codes.
Every stairway having two or more risers serving any building or portion thereof shall comply with the requirements of Section 1003.3.3. For the purposes of Section 1003.3.3, the term “stairway” shall include stairs, landings, handrails and guardrails as applicable. Where aisles in assembly rooms have steps, they shall comply with the requirements in Section 1004.3.2.
Stairs or ladders used only to attend equipment or windows wells are exempt from the requirements of this section.
For the purpose of this chapter, the term “step” shall mean those portions of the means of egress achieving a change in elevation by means of a single riser. Individual steps shall comply with the detailed requirements of this chapter that specify applicability to steps.
1003.3.3.2 Width. The width of stairways shall be determined as specified in Section 1003.2.3, but such width shall not be less than 44 inches (1118 mm), except as specified herein and in Chapter 11. Stairways serving an occupant load less than 50 shall not be less than 36 inches (914 mm) in width.
Handrails may project into the required width a distance of 3 ½ inches (89 mm) from each side of a stairway. Stringers and other projections such as trim and similar decorative features may project into the required width 1 ½ inches (38 mm) from each side.
1003.3.3.3 Rise and run.
The rise of steps and stairs shall not be less than 4 inches (102 mm) nor more than 7 inches (178 mm). The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm). Except as permitted in Sections 1003.3.3.8.1, 1003.3.3.8.2 and 1003.3.3.8.3, the run shall not be less than 11 inches (279 mm) as measured horizontally between the vertical planes of the furthermost projection of adjacent treads of nosings. Stair treads shall be uniform size and shape, except the largest tread run within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm).
- Private steps and stairways serving an occupant load of less than 10 and stairways to unoccupied roofs may be constructed with an 8-inch-maximum (203 mm) rise and a 9-inch-minimum (229 mm) run.
- Where the bottom or top riser adjoins a sloping public way, walk or driveway having an established grade (other than natural earth) and serving as a landing, the bottom or top riser may be reduced along the slope to less than 4 inches (102 mm) in height with the variation in height of the bottom or top riser not to exceed 1 unit vertical in 12 units horizontal (8.3% slope) of stairway width.
Every stairway shall have a headroom clearance not less than 6 feet.
8 inches (2032 mm). Such clearances shall be measured vertically from a plane parallel and tangent to stairway tread nosing to the soffit or other construction above at all points.
There shall be a floor of landing at the top and bottom of each stairway or stair run. Every landing shall have a dimension measured in the direction of travel not less than the width of the stairway. Such dimensions need not exceed 44 inches (1118 mm) where the stair has a straight run. At least one intermediate landing shall be provided for each 12 feet (3658 mm) of vertical stairway rise measured between the horizontal planes of adjacent landings. Landings shall be level except that exterior landings my have a slope not to exceed ¼ unit vertical in 12 units horizontal (2% slope). For landings with adjoining doors, see Section 1003.3.1.7.
- In Group R, Division 3, and Group U Occupancies and within individual units of Group R, Division 1 Occupancies, such length need not exceed 36 inches (914 mm) where the stair has a straight run.
- Stairs serving an unoccupied roof are exempt from these requirements.
Stairways shall have handrails on each side, and every stairway required to be more than 88 inches (2235 mm) of required width. Intermediate handrails shall be spaced approximately equally across with the entire width of the stairway.
- Stairways less than 44 inches (1118 mm) in width or stairways serving one individual dwelling unite in Group R, Division 1 or 3 Occupancy or a Group R, Division 3 congregate residence may have one handrail.
- Private stairways 30 inches (762) or less in height may have a handrail on one side only.
- Stairways having less than four risers and serving one individual dwelling unit in Group R, Division 1 or 3, or a group R, Division 3 congregate residence or Group U Occupancies need not have handrails.
The top of handrails and handrail extensions shall not be placed less than 34 inches (864 mm) nor more than 38 inches (965 mm) above landings and the nosing of treads. Handrails shall be continuous the full length of the stairs and at least one handrail shall extend in the direction of the stair run not less than 12 inches (305 mm) beyond the bottom riser. Ends shall be returned or shall have rounded terminations or bends.
- Private stairways do not require handrail extensions.
- Handrails may have a starting or volute newels with the first tread on stairways in Group R, Division 3 Occupancies and within individual dwelling units of Group R, Division 1 Occupancies.
The handgrip portion of handrails shall not be less than 1¼ inches (32 mm) nor more than 2 inches (51 mm) in cross-sectional dimension or the shape shall provide an equivalent gripping surface. The handgrip portion of handrails shall have a smooth surface with no sharp corners. Handrails projecting from a wall shall have a space of not less than 1 ½ inches (38 mm) between the wall and the handrail.
Stairways open on one or both sides shall have guardrails as required by Section 509.
1003.3.3.8 Alternative stairways.
1003.3.3.8.1 Circular stairways. Circular stairways conforming to the requirements of this section may be used as a means of egress component in any occupancy. The minimum width of run shall not be less than 10 inches (254 mm) and the smaller stairway radius shall not be less than twice the width of the stairway.
1003.3.3.8.2 Winding stairways. In Group R, Division 3 Occupancies and in private stairways in Group R, Division 1 Occupancies, winding stairways may be used if the required width of run is provided at a point not more than 12 inches (305 mm) from the side of the stairway where the treads are narrower, but in no case shall the width of run be less than 6 inches (152 mm) at any point.
1003.3.3.8.3 Spiral stairways. In Group R, Division 3 Occupancies and in private stairways within individual units of Group R, Division 1 Occupancies, spiral stairways may be installed. A spiral stairway is a stairway having a closed circular form in its plan view with uniform section shaped treads attached to and radiating about a minimum diameter supporting column. Such stairways may be used as a required means of egress component where the area served is limited to 400 square feet (37.16m²).
The tread shall provide a clear walking area measuring at least 26 inches (600 mm) from the outer edge of the supporting column to the inner edge of the handrail. The effective tread is delineated by the nosing radius line, exterior arc (inner edge of railing) and the overlap radius line (nosing radius line of tread above). Effective tread dimensions are taken along a line perpendicular to the center line of the tread. A run of at least 7 ½ inches (191 mm) shall be provided at a point 12 inches (305 mm) from where the tread is the narrowest. The rise shall be sufficient to provide a headroom clearance of not less than 6 feet 6 inches (1981 mm): however, such a rise shall not exceed 9 ½ inches (241 mm).
1003.3.3.9 Interior stairway construction.
Interior stairways shall be constructed based on type of construction requirements as specified in Sections 302.4, 603.4, 604.4, 605.4 and 606.4.
Except where enclosed usable space under stairs is prohibited by Section 1005.3.3.6, the walls and soffits of such enclosed space shall be protected on the enclosed side as required for one-hour fire-resistive construction.
Stairways exiting directly to the exterior of a building four or more stories in height shall provide with a means for emergency entry for fire depart access (See the Fire Code.)