What riser height and tread depth does the ADA require for stairs?

Risers must be 4 to 7 inches high, and treads must be at least 11 inches deep measured from nosing to nosing. Both must be uniform across the flight. Note these ranges are different from residential IRC rules, which allow risers up to 7-3/4 inches and treads as shallow as 10 inches.

What height must ADA handrails be, and on which sides?

Handrails are required on both sides of the stair and must be 34 to 38 inches high, measured vertically from the leading edge of each tread nosing. Circular rails must have an outside diameter of 1-1/4 to 2 inches so they are easy to grip.

Do stairs in a single-family home have to meet ADA rules?

No. The ADA covers places of public accommodation, commercial facilities, and public buildings, not typical single-family homes. Residential stairs follow the IRC or local building code instead. Some multifamily housing has separate accessibility rules, so check what applies to your project.

What does the ADA require for stair nosings?

Nosings must not project abruptly beyond the riser face below them, and any curve or bevel on the nosing is limited to a radius of 1/2 inch or less. Open risers are not permitted. Tread surfaces must be stable, firm, and slip resistant.

How far must handrails extend at the top and bottom of stairs?

At the top of the flight, handrails must extend horizontally at least 12 inches beyond the top nosing. At the bottom, they must continue at the stair slope for a horizontal distance equal to at least one tread depth beyond the last nosing. Extensions must return to a wall, guard, or landing surface, or continue to an adjacent flight.

Does a stair need to satisfy both ADA and local building codes?

Yes. The ADA is a federal civil-rights law, not a building permit checklist, so passing ADA does not automatically pass the local building code, and passing local code does not guarantee ADA compliance. Design and inspect for both.

Are detectable warnings required on stair treads?

The 2010 ADA Standards require detectable warning surfaces on curb ramps and certain transit platform edges, not on stair treads themselves. Still, treat any curb ramps and sidewalk transitions on the same accessible route as part of your compliance check.

ADA Stair Calculator

What Is the ADA Stair Calculator?

Check your stair design against the accessibility rules in the 2010 ADA Standards for Accessible Design with this free ADA stair compliance calculator. Section 504 sets the dimensional rules for stairways: every riser must be at least 4 inches and no more than 7 inches high, treads must be at least 11 inches deep measured from nosing to nosing, risers must be closed (no open risers), and nosings must be curved or beveled with a radius of no more than 1/2 inch rather than left as sharp square edges. Section 505 covers handrails: rails are required on both sides of the stair, mounted 34 to 38 inches above the tread nosings, and extended at the top and bottom of the flight so people can grip them before the first step and past the last. The tool also checks the wider context of an accessible route, including minimum clear widths on egress stairs and slip-resistant tread surfaces, and it flags the distinction between ADA rules and local building codes, which both have to be satisfied. This check is intended for commercial buildings, places of public accommodation, and public facilities, where ADA Title III applies. Typical single-family homes are not covered by the ADA, though multifamily housing and local codes bring their own accessibility requirements.

How to Use This Calculator

Enter the riser height of your stair. The tool checks that it falls within the ADA range of 4 to 7 inches and that every riser in the flight is uniform.
Enter the tread depth measured from nosing to nosing. ADA requires at least 11 inches of horizontal depth on each tread.
Confirm the risers are closed. Open risers are not permitted on stairs covered by ADA Section 504.
Describe the nosing profile. Nosings must not project abruptly beyond the face of the riser below, and any curve or bevel is limited to a 1/2-inch maximum radius.
Enter the stair width. The tool compares it against the egress-width rules that apply where the stair is part of an accessible means of egress.
Enter the handrail height on each side, measured vertically from the tread nosing. Both sides must fall within 34 to 38 inches, and handrails are required on both sides of the stair.

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