How steep can stairs be under the California code?

Risers and treads

The rules for stair risers and treads, and their exceptions, are in section R318.7 of the 2025 California Residential Code.

Source: 2025 California Residential Code, Chapter 3 (UpCodes)

Guards on stairs

Guards are required on open-sided floors, stairs, ramps and landings that are more than 30 inches above the floor or grade below at any point within 36 inches of the open edge (R321.1.1).

Insect screening does not count as a guard.

Required guards have to be at least 42 inches high (R321.1.2).

On the open sides of stairs, guards have to be at least 34 inches high, measured from a line along the nosings.

Where the top of a guard on the open side of stairs also serves as the handrail, it has to be at least 34 and no more than 38 inches high, measured from a line along the nosings.

Required guards cannot have openings that a 4-inch sphere can pass through.

Guards on the open side of stairs cannot have openings that a 4-3/8-inch sphere can pass through.

The triangle at the open side of a stair, formed by the riser, the tread and the guard's bottom rail, cannot let a 6-inch sphere pass through.

Source: 2025 California Residential Code, Chapter 3 (UpCodes)

Which code applies

The 2025 California Residential Code took effect on January 1, 2026.

Source: California Building Standards Commission: Codes