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Stairway dimensions, recommendations & building code citations:
This document provides the stair dimensions required by building code specifications and includes sketches, photographs, and examples of defects used in inspecting indoor or outdoor stairs, railings, landings, treads, and related conditions for safety and proper
A Summary of Stairway, Railing & Landing Construction Dimensions, Codes, Standards & Rules
Stairway dimensions & construction requirements & codes are summarized here.
For a complete list of articles on stairs, railings, and ramps, their inspection, trip hazards, and good design,
see STAIRS, RAILINGS, LANDINGS, RAMPS - INSPECTIONS, CODES. Or see these detailed articles on specifications for proper dimensions for stairs, railings, platforms
Because more people are injured by trips and falls than other hazards, experts have looked closely at the specifications for stairs, steps, and rails to reduce the falling hazards.
This work has been translated into stair and railing specifications that are similar among codes and countries (but not identical). -- IBC, IRC, BOCA, Kingston NY Stair Code, & other sources.
Stair and Railing Specification Topics for stair (U.S. and International Residential Codes) include the items listed below.
Stair Dimensions for Straight Stairway Runs: Stair width, landing length
Stairwell width and stair landing platform requirements are summarized by these sketches courtesy Carson Dunlop Associates.
The minimum recommended stair width is between 34" and 36" Across the width of the tread. Some codes such as CA/OSHA specify a minimum stairway width of 24" ..
The minimum recommended stair landing length is 36" (or a length and width sufficiently greater than the swing of the door if a wider door is present.
Is a landing required at the top of stairs?
Ordinarily, yes, a top landing is required. For example most exterior stairs approaching a building entry door encounter a door or storm/screen door that swings out. We need somewhere to stand when opening the door. But a stair top landing is not required if the the stairs rise to a doorway at which the door opens away from the stairwell.
Of course standing one step "down" from the door opening might place the door knob a bit high for shorter users of the entry.
Stairway Height, Width, Headroom Requirements
Stairway headroom or "overhead clearance": the distance from the top of the stair tread to the ceiling above, measured at the stair tread nose, should be six feet eight inches (or more).
(Stairway headroom should be => 6'8" over tread or landing)
Stairway maximum height: the total vertical rise of a straight run of stairs should be twelve feet or less between floors. For higher total rises a landing may be required.
(Stairway maximum height should be <= 12' between floors - this means landings could be required)
Exceptions to stair dimension requirements may be made for stairs giving access to non-living areas of a building such as storage lofts and mechanical rooms. Check with your local building officials.
Specifications for Recommended Minimum Stairway Widths & Stair Lengths
Stairway width should be equal to or greater than 36" of clear unobstructed distance measured at all points above the [permitted] hand-railing height. This is the blue arrow in our photograph below.
Stairway width should also be equal to or greater than 36" of clear unobstructed space between the top of the handraill (the permitted handrailing height) and the required headroom clearance upper height.
For a stairway with a railing on just one side, stairway width can be a bit smaller, with a clear width of 31.5" in the space below the handrail height. [This allows taking into account stair stringer trim such as shown in our photographs. This space is shown with the green arrow in our photograph below.
For a stairway with a handrailing along both sides, the clear stairway width is permitted to be smaller still, with a clear width of 27".
Handrailings should not project more than 4 1/2" into the stairway walking space on either side of the stairway.
Definition of Stairway Width or Stair Width - don't confuse stair width with stair depth
If you stick to using the word stair tread depth you can avoid this confusion.
Oops, that is, unless you start confusing tread depth with stair tread riser height. Stair tread depth is defined above as the horizontal distance from nose to nose or from riser face to nose on open riser stairs.
Stairway width is the horizontal width of the stair opening (blue arrow in our photo). For stairs enclosed by a wall on both sides, usually the stairway width is the distance between those walls.
Stair tread width (green arrow in our photo) is the horizontal left to right width of the stair tread.
At left our photo illustrates three different stair width measurements
Stair tread width (green arrow) (smaller than stairway width due to side trim boards)
Stairway width (blue arrow) over most of this stairway (nominally 36" or wider)
Stairway width near stair top (pink arrow) due to a wall projection (nominally 36" or wider)
Recommended Stairway Width
Stairwell width and stair landing platform requirements are summarized by the sketch above. The measurement locations for determining a stairway width are illustrated in our photo at left, courtesy Galow Homes. In the stairway shown, the owners opted for a 36" wide stairwell.
The minimum recommended stair width is between 34" and 36" across.
Handrailings reduce the nominal stairwell width
In these sketches and in our photographs used here, the required handrails have been omitted for clarity.
Handrailings will protrude into and may reduce the nominal the stairwell width.
For a 36" wide stairwell such as that shown above, the stair railing intrusion is not a problem, but for more narrow stairs it may be, especially where accessible stairways are required.
Handrail Requirements for Wide Stairways
One use of extra-wide stairways is to permit two-way traffic without people punching into one another going up and down the stairs, while at the same time the stairway may also serve large crowds moving usually in one direction at a time.
The divided stairway shown above is at Carnagie Hall in New York City.
The wide stair requires a center handrailing, typically leaving 36" on either side of the center handrail.
Step Riser Height Specifications & Common Stair Construction Mistakes
Stair Step Risers
Step riser specifications riser height (<= 7.75")
Step riser height uniformity (<= 3/8" variation)
Step riser slope (out of vertical) (<= 30 deg measured from horizontal surface of the tread)
Step risers: open risers are permitted provided the opening will not pass a 4" sphere (child safety)
Stair Riser Defects
Stair risers of uneven height - no variation greater than 0.375 inches is allowed
Bad Deck Stair Example: Nothing is right about the exterior stairs shown in our photo from a 1991 home inspection:
This stair stringer is too-deeply notched and could split;
The stair risers are too high, as our client is showing with our tape.
The stair treads do not have enough depth - the treads were made from a single 2x6 (so they are 5 1/2" in depth).
There is no railing on the steps although the height above ground is more than 30".
The deck and platform railing is open with no guardrail balusters.
Closed stair treads using a solid riser are shown at the left of the sketch and
Open stair treads are shown at the right sketch. "Open stair treads" means that no solid riser is installed between the stair treads.
Stair tread nose projection and radius: stair treads should have a projecting nose that is rounded and projecting a maximum of 1.5 " over the tread below.
The requirements for a projecting stair nose over the tread below may be amended for open riser stairs in some jurisdictions, but in no case should the front of a stair tread be more than 1.5" back from the inside edge of the tread below - see sketch annotations. [Click any of our images to see an enlarged, detailed version]
Stair tread thickness: The minimum tread thickness for stair treads supported by risers is 1".
Notice that the minimum stair tread thickness is increased to 1.5" when the stair tread is not supported by a solid riser.
Example Building Code Specifications For Stairway Dimensions
California and other U.S. states often take as a starting point for state building codes pertaining to stair, landing, railing, tread and other stairway design specifications the national model building codes. The California CA/OSHA Section 1003.3.3 Stairways and Landings provisions, as well as the California Building Code (CBC) illustrate:
CA/OSHA: California Stair & Railing Code details
The following stair dimension example citation is from CA/OSHA Subchapter 4. General Industry Safety Orders,
Article 17. Ramps, Runways, Stairwells, and Stairs. Note: this code establishes minimum occupational safety & health standards that apply to all places of employment in California. This is not a residential building code requirement, but this text in our OPINION models stair construction safety & design specifications.
See RAILING CODES & SPECIFICATIONS for model building code specifications of when a handrailing is required, heights, stairway widths, graspability, etc.
CA/OSHA Title 8 Section 1626. Stairwells and Stairs  With added stair details quoting from the CBC 1003.3.3
(a) General. [Stairway width, free space, step rise, step run or depth, tread width & riser height variation permitted]
(1) Stairways shall be al least 24 inches in width and shall be equipped with stair rails, handrails, treads, and landings.
Note: this is a CA/OSHA specification. The CBC 1003.3.3 Stairways and Landings model code states these stairway specifications:
Private stairways shall be a minimum of thirty-six inches wide. Trim and handrails may not encroach into this
minimum width by more than 3 1/2 inches.
The maximum rise of each step is eight inches;
the minimum rise
is four inches.
The minimum run is nine inches.
The largest tread width or riser height in any flight of stairs
shall not exceed the smallest by more than 3/8 inch.
(2) Railings and toeboards meeting the requirements of Article 16 of these safety orders shall be installed around stairwells.
(b) The following requirements apply to all stairways as indicated:
(1) Temporary stairways that will not be a permanent part of the structure on which construction work is being performed shall be at least 24 inches in width. The stairway shall have landings at each floor, or level, of not less than 30 inches in the direction of travel and extend at least 24 inches in width at every 12 feet or less of vertical rise.
(2) Stairs shall be installed between 30° and 50° from horizontal.
(3) Riser height and tread depth shall be uniform within each flight of stairs, including any foundation structure used as one or more treads of the stairs. Variations in riser height or tread depth shall not be over 1/4-inch (0.6 cm) on any stairway.
(4) Where doors or gates open directly on a stairway, a platform shall be provided, and the swing of the door shall not reduce the effective width of the platform to less than 20 inches (51 cm).
(5) Unprotected sides and edges of stairway landings shall be provided with railings. Design criteria for railings are prescribed in Section 1620 of these safety orders.
(6) Metal pan landings and metal pan treads, when used, shall be secured in place before filling with concrete or other material.
(7) All parts of stairways shall be free of hazardous projections, such as protruding nails.
(8) Slippery conditions on a stairway shall be eliminated before the stairway is used to reach another level.
(c) Stair rails and handrails. The following requirements apply to all stairways as indicated:
Some codes (CA/OSHA Title 8 Section 1626) may cause a little confusion between the definition of handrail and guardrail, by adding a third term, "stair rail":
(1) Stairways having four or more risers or rising more than 30 inches (76 cm), whichever is less, shall be equipped with:
(A) At least one handrail and
(B) A stair rail consisting of a top rail and mid-rail along each unprotected side or edge.
See RAILING CODES & SPECIFICATIONS for model building code specifications of when a handrailing is required, heights, stairway widths, graspability, etc.
At least in the 2006 IRC Section R202 these terms are defined clearly:
Definition of guardrail or guard: Guard [or guardrail or guard railing]: A building component or a system of building components located near the open sides of elevated walking surfaces that minimizes the possibility of a fall from the walking surface to a lower
Definition of "stair rail" as guardrail: In general people speak of guardrails or guards as installed along balconies or elevated walkways and decks. When we enclose open side(s) of a stairway with a "guardrail" some codes such as the 2006 IRC Section R202 use the unfortunate term "stair rail". More unfortunate if readers don't continue along to discover that the horizontal members described in ((B) above must be further enclosed with balusters.
Definition of handrail or hand railing: Handrail [or hand railing] . A horizontal or sloping rail intended for grasping by the hand for guidance or support.
See HANDRAILS & HANDRAILINGS for details about stairway handrailing dimensions, graspability, railing heights, railing continuity, termination, projection distances and all other parameters.
(d) Temporary Service [stairs] - Temporary service stairs, treads, landings:
The following requirements apply to all stairways as indicated:
(1) Except during stairway construction, foot traffic is prohibited on stairways with pan stairs where the treads and/or landings are to be filled in with concrete or other material at a later date, unless the stairs are temporarily fitted with wood or other solid material at least to the top edge of each pan.
(2) Except during stairway construction, foot traffic is prohibited on skeleton metal stairs where permanent treads and/or landings are to be installed at a later date, unless the stairs are fitted with secured temporary treads and landings long enough to cover the entire tread and/or landing area.
(3) Treads for temporary service shall be made of wood or other solid material, shall cover the full width and depth of the stair and shall be supported to prevent undue deflection.
(4) Temporary treads and landings shall be replaced when worn below the level of the top edge of the pan.
Reader Question: 10 Feb 2015 Do exterior contrete stairs leading to two terraces apartments have to be a certain width? One owner wishes to put in chairlift up side of staircase railing. Stairs are 84cm wide. said:
Do exterior contrete stairs leading to two terraces apartments have to be a certain width? One owner wishes to put in chairlift up side of staircase railing. Stairs are 84cm wide.
Stairway width (in the U.S. - you don't say where you are located) should be equal to or greater than 36" of clear unobstructed distance measured at all points above the [permitted] hand-railing height.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Eric Galow, Galow Homes, Lagrangeville, NY. Mr. Galow can be reached by email: email@example.com 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 firstname.lastname@example.org 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
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Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: email@example.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
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