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ADAAG Manual

Stairs [4.9]

Scoping [4.1.3(4)]

Specifications in 4.9 benefit people who have difficulty walking or using stairs. Compliance is required where stairs are the only connection between two levels, such as between floors in buildings without elevators. Stairs do not have to comply where vertical access (ramp, elevator, or lift) is provided. In this case, compliance is still a good idea since some people with walking impairments may prefer stairs to ramps or wheelchair lifts. Also, most building codes require stairs to comply with similar requirements. Where compliance is required, 4.9 applies to all stairs between levels not connected by an accessible means.

Accessible Route

Stairs are not considered part of an accessible route but where they are required to comply with 4.9, it is recommended that routes to them meet the requirements for accessible routes since certain specifications, such as clear width, can benefit people with walking impairments able to use stairs and those who use service animals.


ADAAG does not specify the minimum number of steps that comprise a set of "stairs." Most building codes require handrails for a certain change in level or number of steps. (In new construction, the requirement for accessible routes usually makes compliance with 4.9 optional).

Egress Stairs

The requirement for a minimum 48 inch width between handrails is specific to stairs adjacent to areas of rescue assistance and does not apply generally to stairs covered by 4.9.

Assembly Areas

Because handrails may interfere with egress where they adjoin seating and since accessible routes are required to connect to wheelchair seating locations, compliance with 4.9, including requirements for handrails, is not required at sides of stairs adjacent to seating in assembly areas.

Treads and Risers [4.9.2], Nosings [4.9.3]

Treads must be at least 11 inches wide and uniform. Uniformity is important not only between steps but along each step; curved stairs, where the width of each tread varies, do not meet this requirement. Variation in riser height along a set of stairs can be a tripping hazard. ADAAG requires the height to be uniform but does not specify a minimum or maximum height which is addressed by most local building codes. (The CABO/ANSI A117.1‒1992 standard requires a riser height between 4 to 7 inches.)

People without full use of a leg may drag a foot when ascending stairs. A smooth transition from tread to tread is essential. Open risers and abrupt or extended nosings (i.e., projecting more than 1 1/2 inches) can catch the toe. Angled or rounded nosings or sloped risers help prevent this hazard and provide a smoother transition. Straight risers without nosings are acceptable. ADAAG specifies the radius of the curvature of the leading edge of treads and the underside slope of angled or rounded nosings.

Handrails [4.9.4]

Continuous handrails are required along both sides of stairs. A center rail is not specified for wide stairways by ADAAG but may be required by local building or life safety codes.

Shape and Diameter

Use of a handrail requires the formation of a power grip so that hands and fingers can be opposed and the surface of the palm can be in maximum contact with the rail surface. Large sections, particularly those of rectangular design, are not as graspable as smaller circular sections. A gripping surface width between 1¼ to 1½ inches diameter is specified. Also permitted are rails that allow an opposing grip similar to that possible with a circular section of 1¼ to 1½ inches diameter. Standard IPS pipe designated as 1¼ to 1½ inch is acceptable. (Consider a 1¼ inch specification for pipe since a 1½ inch specification may result in an outer diameter close to 2 inches.) The 1½ inch clearance between walls and handrails is an absolute dimension; it provides knuckle clearance while preventing entrapment of the arm for people who lean on rails with their forearm.


Extensions at the top provide support before the first step is made. The bottom extension is especially important in providing this support until one is fully vertical. For extensions to provide this support, they must be in line with the direction of travel on the stairs. Extensions are not required in alterations if they project into cross circulation paths. Extensions must be rounded or returned to the walls, floors, or posts. Requirements for protruding objects in 4.4 limit post-mounted overhangs to 12 inches if the leading edge is higher than 27 inches from the floor.

Detectable Warnings at Stairs [4.9.5]

A requirement for detectable warnings has not been specified because of lack of data regarding effectiveness.


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