The California stair code lives inside Title 24, the California Building Standards Code, which sets minimum dimensions, handrail specifications, guard heights, headroom, lighting, and landing requirements for every stairway built in the state.1Department of General Services. CBSC Frequently Asked Questions The specific numbers depend on whether your project falls under the California Residential Code (CRC) or the California Building Code (CBC), and workplace stairs answer to a separate set of rules under Cal/OSHA. Local building departments enforce all of this, and a stair that misses a dimension by a fraction of an inch can hold up your certificate of occupancy until it is corrected.
Which Code Governs Your Project
The California Residential Code covers detached one- and two-family dwellings and townhouses up to three stories.1Department of General Services. CBSC Frequently Asked Questions Everything else — commercial buildings, apartment complexes, mixed-use structures, schools, public facilities — falls under the California Building Code. The CRC allows slightly more generous stair dimensions on the theory that residents use the same stairs daily. The CBC is stricter because commercial and public stairs see higher traffic from first-time users.
Both codes are part of Title 24, published by the California Building Standards Commission and applied statewide.2Department of General Services. Codes Local jurisdictions adopt Title 24 as a baseline and sometimes add amendments, so call your local building department before you frame anything.
One boundary worth flagging up front: if the stair is in a workplace, Cal/OSHA’s Title 8 rules apply on top of Title 24, with slightly different numbers. Those are covered at the end.
Riser Height, Tread Depth, and Width
These two measurements — how tall each step is and how deep each tread is — control whether a stair feels safe underfoot. The code sets them by building type:
- Under the CBC (commercial and public buildings), the maximum riser height is 7 inches, minimum riser height is 4 inches, and minimum tread depth is 11 inches.
- Under the CRC (residential dwellings), the maximum riser height is 7¾ inches and the minimum tread depth is 10 inches.3County of Sonoma. B-09 2020-Current: Code Requirements for Residential Stairs
Tread depth is measured horizontally between the vertical planes of the front edges (nosings) of adjacent treads. Riser height is the vertical distance between the top surfaces of consecutive treads.
Width depends on how many people the stair serves. Residential stairs must be at least 36 inches wide.3County of Sonoma. B-09 2020-Current: Code Requirements for Residential Stairs Under the CBC, stairs serving more than 50 occupants must be at least 44 inches wide; stairs serving 50 or fewer can be 36 inches.
The ⅜-Inch Uniformity Rule
Within a single flight, the tallest riser and the shortest riser cannot differ by more than ⅜ of an inch.4City of Gilroy. Residential Stairways, Handrails, and Guards The same ⅜-inch tolerance applies to tread depth. This is where a lot of stairs fail inspection. If you are building over an uneven subfloor, account for that unevenness before setting your riser heights, not after.
Winders and Spiral Stairs
Winders
Winder treads (the pie-shaped ones that turn a corner) must have a minimum depth of 10 inches at the walk line, typically taken 12 inches from the narrow side, and cannot be less than 6 inches deep at the narrowest point.3County of Sonoma. B-09 2020-Current: Code Requirements for Residential Stairs The 6-inch minimum at the narrow end is where tight-footprint designs fail. Run the geometry before framing, because there is no variance once the inspector measures it.
Spiral Stairs
Spiral stairs are permitted under the CRC but come with tighter constraints. Minimum tread depth at the walk line is 7½ inches, maximum riser height is 9½ inches, and minimum clear width is 26 inches.3County of Sonoma. B-09 2020-Current: Code Requirements for Residential Stairs Headroom for spirals is 78 inches, two inches less than a standard stair. Because of the narrow width, spirals in residential buildings typically serve a single dwelling unit with a small occupant load.
Handrails
Handrails must sit between 34 and 38 inches above the sloped plane connecting the front edges of the treads.5California Code of Regulations. Title 8, Section 3214 – Stair Rails and Handrails At least one handrail is required. Commercial stairs wider than 44 inches generally need handrails on both sides.
Graspability
The code splits handrail profiles into two types. Type I circular handrails need an outside diameter between 1¼ and 2 inches. Non-circular Type I handrails need a perimeter between 4 and 6¼ inches and a cross-section no wider than 2¼ inches.6Alameda. Guardrails and Handrail Requirements Type II handrails allow a larger profile, share the same 4-to-6¼-inch perimeter range, and must include a finger recess at least ¾ inch deep so a hand can still wrap around them.
A minimum clearance of 1½ inches must be kept between the handrail and the wall or any adjacent surface. That gap keeps knuckles off the wall and allows a continuous grip.
Extensions
Where accessibility is required, handrails must extend horizontally at least 12 inches beyond the top riser and continue to slope for the depth of one tread beyond the bottom riser.7U.S. Access Board. Chapter 5: Stairways In a private residence not required to be accessible, the handrail can simply run from the top riser to the bottom riser without extensions.
Guards
Guards (guardrails) are the barriers on the open side of a stair, landing, or elevated walking surface. Their job is preventing falls over the edge, which is different from a handrail’s job of providing a grip. Confusing the two is one of the most common code mistakes.
Height
The standard guard height is 42 inches above the walking surface, both commercial and residential.8Department of Industrial Relations. California Code of Regulations, Title 8, Section 3209 – Standard Guardrails On the open side of a stair, that 42-inch minimum is measured vertically from the line connecting the tread nosings.
There is one residential exception. In Group R-3 occupancies (single-family homes) and individual dwelling units in Group R-2 (apartments and condos), if the top rail of the guard also serves as the handrail, the height drops to between 34 and 38 inches, measured from the tread nosing line.9County of San Diego. Guards and Handrails This only applies when the guard doubles as the handrail. If a separate handrail is mounted to the guard, the guard itself still needs to reach 42 inches.
The Sphere Rules
No opening in the guard system can allow a 4-inch sphere to pass through. The 4-inch sphere approximates the size of a small child’s head.4City of Gilroy. Residential Stairways, Handrails, and Guards One exception applies to the triangular gap formed where the bottom rail meets a riser and tread on the open side of the stair. That triangle can allow up to a 6-inch sphere, because the geometry prevents a child from fitting through at the larger size.10City of San Dimas. Stairs, Handrails and Guards Openings on the sides of stair treads specifically cannot allow a sphere of 4⅜ inches to pass.
Landings, Headroom, and Doors
Landings
A landing is required at the top and bottom of every flight. Each landing must be at least as wide as the stair it serves and at least 36 inches deep in the direction of travel. The maximum vertical rise between any two landings is 12 feet, so a floor-to-floor height over 12 feet needs an intermediate landing.
Doors that open onto a stair landing cannot reduce the landing dimension below 42 inches in any position, and a fully open door cannot project more than 3 inches into the required stair width. Residential remodels that add a doorway at the top or bottom of an existing staircase are where this rule catches people.
Headroom
Minimum headroom is 6 feet 8 inches (80 inches) above the treads and landings under both the CBC and CRC. It is measured vertically from the line connecting the tread nosings up to the ceiling or lowest obstruction. Clearance must hold at every point along the stair and across the full landing. Soffits, ductwork, and beams that drop below 80 inches will fail inspection. Spiral stairs are the exception at 78 inches.3County of Sonoma. B-09 2020-Current: Code Requirements for Residential Stairs
Lighting
Every interior stairway must have artificial lighting. The 2022 California Building Code requires 10 footcandles of illumination on exit stairways, up from 1 footcandle in earlier editions. Under the CRC, when a residential stair has six or more risers, a light fixture controlled by a wall switch is required at both the top and the bottom.
Permits and Inspections
New stairway construction and significant modifications generally require a building permit. The threshold is whether the work involves structural changes or affects the means of egress. Replacing treads and handrails in kind, with the same dimensions and materials, may not require a permit in some jurisdictions. Altering layout, dimensions, or structural support almost always does.
Framing inspection typically happens before walls are closed up or finishes go on. Riser uniformity, tread depth, landing dimensions, guard height, and handrail graspability all get checked at this stage. A stair that fails must be corrected before the building department issues a certificate of occupancy. Some jurisdictions issue a temporary certificate when the noncompliance is not a substantial hazard, but those come with expiration dates and additional fees.11eCode360. Ordinance 1719 Adopting the 2025 California Building Codes Measure twice, frame once, and resolve any dimension question with the local building department before the concrete sets.
Workplace Stairs Under Cal/OSHA
Title 24 is not the only rulebook. Cal/OSHA enforces separate workplace stair standards under Title 8 of the California Code of Regulations, and they apply independently.
Under Title 8, the maximum riser height is 7½ inches (versus 7 inches under the CBC), and the minimum tread run is 10 inches (versus 11 inches under the CBC). Width follows the same occupant-load tiers: 44 inches for more than 50 occupants, 36 inches for 50 or fewer, and 30 inches for private stairways serving fewer than 10 people. The ⅜-inch uniformity tolerance is identical. Workplace headroom is 6 feet 6 inches, two inches less than the building code requires.12California Code of Regulations. Title 8, Section 3231 – Stairways Handrail height matches the building code at 34 to 38 inches for stairs installed after April 3, 1997; older workplace stairs may still be compliant with handrails as low as 30 inches under the grandfathered standard.5California Code of Regulations. Title 8, Section 3214 – Stair Rails and Handrails
If you are renovating a workplace, both the building code and the Cal/OSHA rules apply. Where they conflict, meet whichever is more restrictive.