U.S. ADA Stair & Handrail Design
How to build stairs & railings in compliance with the Americans with Disabilities Act or ADA
ADA STAIR & RAIL SPECIFICATIONS - CONTENTS: Stair building specifications for compliance with the U.S. Americans with Disabilities Act - ADA Stair Specifications for treads, risers, tread nosing, and handrailings for safe, accessible stairs
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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.
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. 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.
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[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:
[Click to enlarge any image - arrows & heavy lines in these illustrations were added by InspectApedia.com ]
(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).
[Click to enlarge any image]
(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.
(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: www.ada.gov, 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
"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: www.ada.gov, Tel: 1-800-514-0301, TTY: 1-800-514-0383
Americans with Disabilities Act of 1990, As Amended, Full Text, provided by ada.gov - Website: http://www.ada.gov/pubs/adastatute08.htm, retrieved 5 July 2015 Note: This link provides the current full-text of the Americans with Disabilities Act of 1990 (ADA), including changes made by the ADA Amendments Act of 2008 (P.L. 110-325), which became effective on January 1, 2009. This is a very large document that covers many topics beyond steps and railings discussed in this InspectApedia.com article series.
The ADA was originally enacted in public law format and later rearranged and published in the United States Code.
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.
U.S. Department of Justice, "Americans with Disabilities Act Title III Regulations", [Book for sale at Amazon.com]
Abstract: This final rule revises the Department of Justice (Department) regulation that implements title III of the Americans with Disabilities Act (ADA), relating to nondiscrimination on the basis of disability by public accommodations and in commercial facilities. The Department is issuing this final rule in order to adopt enforceable accessibility standards under the Americans with Disabilities Act of 1990 (ADA) that are consistent with the minimum guidelines and requirements issued by the Architectural and Transportation Barriers Compliance Board, and to update or amend certain provisions of the title III regulation so that they comport with the Department’s legal and practical experiences in enforcing the ADA since 1991.
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.
1995 CABO 314.2 allows a maximum 2% slope on stair treads. The 1:48 (2%) max. will also comply with the accessibility requirements of ICC/ANSI A117.1-1998. I also agree that UBC 1003.3.3.5 applies.
2000 IBC 1003.3.3.5.1 - "The walking surface of treads and landings of a stairway shall not be sloped steeper than one unit vertical in 48 units horizontal in any direction."
2000 IBC 1003.3.3.5.2 - "Outdoor stairways and outdoor approaches to stairways shall be designed so that water will not accumulate on walking surfaces."
28 CFR Part 36 - 4.9.6 - "Outdoor stairs and their approaches shall be designed so that water will not accumulate on walking surfaces."
1998 ADAAG - 4.9.6 - same as above.
CC/ANSI A117.1-1998 - 504.7 - "Outdoor stairs and outdoor approaches to stairs shall be designed so that water will not accumulate on walking surfaces."
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.
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Eric Galow, Galow Homes, Lagrangeville, NY. Mr. Galow can be reached by email: firstname.lastname@example.org or by telephone: 914-474-6613. Mr. Galow specializes in residential construction including both new homes and repairs, renovations, and additions.
 "The Elimination of Unsafe Guardrails, a Progress Report," Elliott O. Stephenson, Building Standards, March-April 1993
 "Are Functional Handrails Within Our Grasp" Jake Pauls, Building Standards, January-February 1991
 Access Ramp building codes:
 Access Ramp Standards:
ADA (Americans with Disabilities Act), Public Law 101-336. 7/26/90 is very often cited by other sources for good design of stairs and ramps etc. even where disabled individuals are not the design target.
ANSI A117.4 Accessible and Usable buildings and Facilities (earlier version was incorporated into the ADA)
ASTM F 1637, Standard Practice for Safe Walking Surfaces, (Similar to the above standard
 Falls and Related Injuries: Slips, Trips, Missteps, and Their Consequences, Lawyers & Judges Publishing, (June 2002), ISBN-10: 0913875430 ISBN-13: 978-0913875438 "Falls in the home and public places are the second leading cause of unintentional injury deaths in the United States, but are overlooked in most literature. This book is unique in that it is entirely devoted to falls. Of use to primary care physicians, nurses, insurance adjusters, architects, writers of building codes, attorneys, or anyone who cares for the elderly, this book will tell you how, why, and when people will likely fall, what most likely will be injured, and how such injuries come about. "
 The National Institute of Standards and Technology, NIST (nee National Bureau of Standards NBS) is a US government agency - see www.nist.gov
"A Parametric Study of Wall Moisture Contents Using a Revised Variable Indoor Relative Humidity Version of the "Moist" Transient Heat and Moisture Transfer Model [copy on file as/interiors/MOIST_Model_NIST_b95074.pdf ] - ", George Tsongas, Doug Burch, Carolyn Roos, Malcom Cunningham; this paper describes software and the prediction of wall moisture contents. - PDF Document from NIS
 Slips, Trips, Missteps and Their Consequences, Second Edition, Gary M. Bakken, H. Harvey Cohen,A. S. Hyde, Jon R. Abele, ISBN-13: 978-1-933264-01-1 or
ISBN 10: 1-933264-01-2,
available from the publisher, Lawyers ^ Judges Publishing Company,Inc., www.lawyersandjudges.com email@example.com and also from the InspectAPedia Bookstore (Amazon.com)
 The Stairway Manufacturers' Association, (877) 500-5759, provides a pictorial guide to the stair and railing portion of the International Residential Code. [copy on file as http://www.stairways.org/pdf/2006%20Stair%20IRC%20SCREEN.pdf ] -
 Mold-Resistant Building Practices, advice from an expert on how to prevent mold after a building flood and how to prevent mold growth in buildings by selection of building materials and by anti-mold construction details.
 "The Dimensions of Stairs", J. M. Fitch et al., Scientific American, October 1974.
 Stair & Walkway Standards for Slipperiness or Coefficient of Friction (COF) or Static Coefficient of Friction (SCOF)
ASTM D-21, and ASTM D2047
UL-410 (similar to ASTM D-21)
NSFI 101-B (National Floor Safety Institute)
NSFI Walkway Auditing Guideline (WAG) Ref. 101-A& 101-B (may appear as ANSI B101.0) sets rules for measuring walkway slip resist
OSHA - (Dept of Labor CFR 1910.22 does not specify COF and pertains to workplaces) but recognizes the need for a "qualified person" to evaluate walkway slipperiness
ADA (relies on the ANSI and ASTM standards)
 A. Sacher, International Symposium on Slip Resistance: The Interface of Man, Footwear, and Walking Surfaces, Journal of Testing and Evaluation (JTE), ISSN: 1945-7553, January 1997 [more focused on slipperiness of polished surfaces
 Algae is widely recognized as a slippery surface - a Google web search for "how slippery is algae on steps" produced more than 15,000 results on 8/29/12)
 Slipperiness of algae on walking surfaces, warning, Royal Horticultural Society, retrieved 8/29/2012, original source: http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=418
 Slipperiness of algae: "Watch your step, wet rocks and algae are slippery" Oregon State University warning 1977 retrieved 8/29/2012, original source: http://www.worldcat.org/title/watch-your-step-wet-rocks-and-algae-are-slippery/oclc/663683915
 Coefficient of friction of algae on surfaces [like stair treads]: Delphine Gourdon, Qi Lin, Emin Oroudjev, Helen Hansma, Yuval Golan, Shoshana Arad, and Jacob Israelachvili, "Adhesion and Stable Low Friction Provided by a Subnanometer-Thick Monolayer of a Natural Polysaccharide", Langmuir, 2008 pp 1534-1540, American Chemical Society,
retrieved 8/29/2012, Abstract: Using a surface forces apparatus, we have investigated the adhesive and lubrication forces of mica surfaces separated by a molecularly thin, subnanometer film of a high-molecular-weight (2.3 MDa) anionic polysaccharide from the algae Porphyridium sp. adsorbed from aqueous solution. The adhesion and friction forces of the confined biopolymer were monitored as a function of time, shearing distance, and driving velocity under a large range of compressive loads (pressures). Although the thickness of the dilute polysaccharide was < 1 nm, the friction was low (coefficient of friction = 0.015), and no wear was ever observed even at a pressure of 110 atm over 3 decades of velocity, so long as the shearing distances were less than twice the contact diameter. Atomic force microscopy in solution shows that the biopolymer is able to adsorb to the mica surface but remains mobile and easily dragged upon shearing. The adhesion (adsorption) of this polysaccharide even to negatively charged surfaces, its stable low friction, its robustness (high-load carrying capacity and good wear protection), and the weak (logarithmic) dependence of the friction force on the sliding velocity make this class of polyelectrolytes excellent candidates for use in water-based lubricant fluids and as potential additives to synovial fluid in joints and other biolubricating fluids. The physical reasons for the remarkable tribological properties of the ultrathin polysaccharide monolayer are discussed and appear to be quite different from those of other polyelectrolytes and proteins that act as thick “polymer brush” layers.
 Jason R. Stokes, Lubica Macakova, Agnieszka Chojnicka-Paszun, Cornelis G. de Kruif, and Harmen H. J. de Jongh, "Lubrication, Adsorption, and Rheology of Aqueous Polysaccharide Solutions, Langmuir 2011 27 (7), 3474-3484
 "Coefficients of Friction for Ice", The Physics Factbook™, Glenn Elert, Ed., retrieved 8/29/12, original source: http://hypertextbook.com/facts/2004/GennaAbleman.shtml
 "Coefficients of Friction for Ice", The University of the State of New York Reference Tables for Physical Setting/Physics. New York: The State Education Department, 2002. Op. Cit.
 Serway Physics for Scientists and Engineers 4th edition (p. 126.)
 "How Slippery Is It", retrieved 8/29/12, original source http://www.icebike.org/Articles/howslippery.htm
 John E. Hunter, "Friction Values", The Source, Society of Accident Reconstructionists, Winter 1998. Study of frictional values of car tires involved in collisions on snow or ice covered roadways.
 Frictional Coefficients of some Common Materials and Materials Combinations, The Engineering Toolbox, retrieved 8/29/2012, original source: http://www.engineeringtoolbox.com/friction-coefficients-d_778.html [copy on file as Friction and Coefficients of Friction.pdf ]
 Stairways and Ladders, A Guide to OSHA Rules, OSHA, U.S. Department of Labor, 3124-12R 2003 - Web Search 05/28/2010 original source: http://www.osha.gov/Publications/osha3124.pdf. OSHA regulations govern standards in the construction industry and in the workforce Quoting from OSHA whose focus is on workplace safety and so excludes discussion of falls and stair-falls in private homes:
OSHA estimates that there are 24,882 injuries and as many as 36 fatalities per year due to falls from stairways and ladders used in construction. Nearly half of these injuries are serious enough to require time off the job--11,570 lost workday injuries and 13,312 non-lost workday injuries occur annually due to falls from stairways and ladders used in construction. These data demonstrate that work on and around ladders and stairways is hazardous. More importantly, they show that compliance with OSHA's requirements for the safe use of ladders and stairways could have prevented many of these injuries. -osha.gov/doc/outreachtraining/htmlfiles/stairlad.html
 International Building Code, Stairway Provisions, Section 1009: Stairways and Handrails, retrieved 8/29/12, original source: http://www.amezz.com/ibc-stairs-code.htm [copy on file as IBC Stairs Code.pdf]
 Model Building Code, Chapter 10, Means of Egress, retrieved 8/29/12, original source: http://www2.iccsafe.org/states/newjersey/NJ_Building/PDFs/NJ_Bldg_Chapter10.pdf, [copy on file as NJ_Bldg_Chapter10.pdf] adopted, for example by New Jersey. International Code Council, 500 New Jersey Avenue, NW, 6th Floor, Washington, DC 20001, Tel: 800-786-4452
 "Right Triangle Angle And Side Calculator", csgnetwork, retrieved 9/29/12, original source: http://www.csgnetwork.com/righttricalc.html -
Online sine / cosine functions permit calculation of lengths of sides of a triangle.
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