ADA Figure 19c Handrail bottom extensionsU.S. ADA Stair & Handrail Design Specifications
How to build stairs & railings in compliance with the Americans with Disabilities Act or ADA

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ADA Stair Specifications for stair & handrailing compliance with the Americans with Disabilities Act:

In the United States stair specifications for accessible stairways and safe, climbable steps and handrailings are discussed by the Americans with Disabilities Act, section 4.9, Stairs provided and illustrated here.

The US ADA section 4.9 includes detailed advice for accessible stair design including stair riser height, stair tread dimensions, stair nosings, handrailings, hand railing continuity, and handrailing extensions at the top and bottom of stairways. This article series describes how to build safe, accessible stairs & handrailings.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

U.S. ADA Stair & Railing Specifications

ADA Figure 19 Stair Tread & Riser DimensionsIn the United States stair specifications for accessible stairways and safe, climbable steps and handrailings are discussed by the Americans with Disabilities Act, section 4.9, Stairs provided and illustrated here.

You will see from the quotation below that the ADA section 4.9 "Stairs" does not explicitly discuss short or low-riser stair steps nor "easily-climbable stairs" but instead is focused on step and railing standards to avoid falling hazards on normal stair dimensions.

U.S. ADA Section 4.9 Stair

4.9.1* Minimum Number. Stairs required to be accessible by 4.1 shall comply with 4.9.

4.9.2 Treads and Risers. On any given flight of stairs, all steps shall have uniform riser heights and uniform tread widths. Stair treads shall be no less than 11 in (280 mm) wide, measured from riser to riser. Open risers are not permitted.

[Click to enlarge any image]

[Note: this ADA detail for 11-inch stair tread width refers to what some specifications call stair tread "depth" - the distance from stair nose to stair riser on an individual stair tread.

The ADA specification measures from riser to riser, essentially excluding the additional amount of tread depth afforded by the tread nosing.

This makes sense in that nosings are typically rounded and are not a safe walking surface, nor do they support the stairway user's foot. - Ed.]

Each stair tread is 11 inches (280 mm) deep minimum with a sloped riser. The nosing shall project no more than 1-1/2 inches (38 mm). [ADA Figure 18a above]

4.9.3 Nosings. The undersides of nosings shall not be abrupt. The radius of curvature at the leading edge of the tread shall be no greater than 1/2 in (13 mm). Risers shall be sloped or the underside of the nosing shall have an angle not less than 60 degrees from the horizontal. Nosings shall project no more than 1-1/2 in (38 mm).

4.9.4 Handrails. Stairways shall have handrails at both sides of all stairs. Handrails shall comply with 4.26 and shall have the following features:

ADA Figure 19a continuous handrails

[Click to enlarge any image - arrows & heavy lines in these illustrations were added by ]

(1) Handrails shall be continuous along both sides of stairs. The inside handrail on switchback or dogleg stairs shall always be continuous. [ADA Figure 19a above and ADA Figure 19b below].

[In ADA Figure 19a Stair Handrails - Plan, note that dimension X is the 12-inch minimum handrail extension that is required at each top riser (the top-most step) and Y is the minimum handrail extension of 12-inches plus the width of one tread that is required at the bottom of each bottom riser (the bottom-most step).

From our observations of implementation of this ADA specification it is permissible to make these horizontal extensions longer than the minimum given in the ADA.- Ed.]

Handrails that are not continuous must have a horizontal extension at the top and bottom of the run. A minimum 12 inch (305 mm) horizontal extension is required at each top riser (indicated in the figure by the dimension X).

A minimum 12 inch (305 mm) horizontal extension plus the width of one tread is required at each bottom riser (indicated by the dimension Y).

ADA Fig 19b Handrails in Elevation

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(2) If handrails are not continuous, they shall extend at least 12 in (305 mm) beyond the top riser and at least 12 in (305 mm) plus the width of one tread beyond the bottom riser.

At the top, the extension shall be parallel with the floor or ground surface. At the bottom, the handrail shall continue to slope for a distance of the width of one tread from the bottom riser; the remainder of the extension shall be horizontal.

ADA Figure 19c Handrail bottom extensions

[Click to enlarge any image]

[See ADA Figure 19 c just above, and ADA Figure 19 d below] Handrail extensions shall comply with 4.4.

ADA Figure 19c Handrail bottom extensions

(3) The clear space between handrails and wall shall be 1-1/2 in (38 mm).

(4) Gripping surfaces shall be uninterrupted by newel posts, other construction elements, or obstructions.

(5) Top of handrail gripping surface shall be mounted between 34 in and 38 in (865 mm and 965 mm) above stair nosings.

(6) Ends of handrails shall be either rounded or returned smoothly to floor, wall or post.

(7) Handrails shall not rotate within their fittings.

4.9.5 Detectable Warnings at Stairs. (Reserved).

4.9.6 Outdoor Conditions. Outdoor stairs and their approaches shall be designed so that water will not accumulate on walking surfaces.

- "2010 ADA Standards for Accessible Design", U.S. Americans with Disabilities Act, 1990, U.S. Department of Justice, & revised Title II & Title III 2010, Website:, Tel: 1-800-514-0301, TTY: 1-800-514-0383

Also see our discussion of stair headroom and ADA 307.2 on protruding objects at STAIR HEADROOM

Books, Citations, Products & Research for ADA Stairs - ADAAG Americans with Disabilities Act Accessibility Guidelines

STAIR HEADROOM includes a discussion of 307 Protruding Objects a section of the U.S. ADA standards on protruding object hazards such as the under-stair area illustrated at left.




Stair Slope Codes (not in the US ADA)

The following model building codes, not part of the U.S. ADA, discuss allowable stair slopes. Stair codes talk about slope chiefly when discussing how much out of level a stair tread may be from front to rear or from side to side to avoid a slip and fall hazard.

But the maximum stair slope for the overall stairway for stairs used as a public passageway between levels is also implicit in the maximum step riser height - typically 8" or in some codes such as New York, 8.25" maximum riser height.


Continue reading at STAIR RISE & RUN CALCULATIONS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.




Or see STAIR HEADROOM including standards on avoiding projecting hazards for the visually impaired

Or see these

Adaptive Design Articles

Or see this

Article Series Contents

The last two articles cited above give details of common building code specifications for allowable stair landing dimensions and step riser and tread dimensions


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Publisher - Daniel Friedman