Winding or Turned Stairways: Guide to Stair Winders & Angled Stairs: Codes, Construction & Inspection

Stair winder specifications & codes for stairs that turn - angled stair treads
- Definitions & Illustrations of Stairs that are Curved or Angled, & Winder Stairs
- What are the minimum tread width and radius for curving stair treads
- Sketches of curved or angled stair design requirements
- Limits on Number of Winder Stair Turns
- Photos of Unsafe Winder or Angled Steps & Stairs
- Angled Stairs Trip & Fall Hazards
Questions & Answers about winder or curved, turned or angled stairways & landings
References

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Winder stairs, angled, or curved stair specifications: this document defines winder stairs refers to building code specifications, construction specs, and inspection details for winder, curved or angular stairs: stairs that make a turn without a landing. We include sketches, photographs, and examples of defects used in inspecting indoor or outdoor stairs, railings, landings, treads. The angled stairs shown at page top are not "winders" but also involve irregularly-shaped stair treads. That photo shows angled stair treads squeezing a stairway onto a New York City sidewalk.

Definition of & Specifications for Winder Stairs - Angled or Curved Steps & Stairways

Definition & Properties of Winder Stair Hazards

Winder Stairs with Dangerous Railing (C) Daniel Friedman San Miguel de Allende 2012

"Winder" or "curved" stairs refer to stairways that make a turn without including an intermediate landing or platform to provide a flat rectangular turning space. Angled or curved or winder stair treads are a particular trip hazard, especially because of the lack of uniformity and because the tread width at the inside of the angle curve can be too small for safe walking.

Definition of Winder Stairs

Any stairway whose treads do not have parallel edges - IRC R-202 - [14a]

By this definition a circular or spiral stair or curved stair is a winder stairway. What's different, then between a circular stair and a more generic winder stair? Check the photos and descriptions of circular stairs and spiral stairs just above.

Winding or spiral stairways must have a handrail to prevent use of areas where the tread width is less than 6 inches (15 cm).

CA/OSHA Title 8 Section 1626 [paragaraph (1) provides:

1926.1052(c)(2) Winding and spiral stairways shall be equipped with a handrail offset sufficiently to prevent walking on those portions of the stairways where the tread width is less than 6 inches (15 cm).

Watch out: we have on occasion seen placement of handrailings close to the origin of turning axis of winder stairs, such as shown by the red arrows in our photograph at left.

This stair installation has no graspable handrailing along the left side of the upper portion of the stairway. So the very handrail intended to prevent use of the too-small tread area actually does not form a barrier along those treads (it is installed on the last rectangular tread above the triangular steps) and worse, because of the lack of anything else to grasp, the walker actually has to hold on to a guard or rail that directs him or her to step precisely where we don't want - on the tiniest part of the tread.

The building owners added the vertical grab-bar and short "handrailing" shown (orange arrow) in our photo. Indeed this gives the stairway user something to grasp on-to.

Unfortunately it also directs the descending or ascending stair user to walk along the inside (red arrow) of several triangular stair treads.

By mounting the graspable handrail close to the innermost point or origin of the winder stair (or circular or spiral stair) turn, you encourage or even force stairway users to walk on the smallest (and most hazardous) portions of the stair treads.

Limits on Number of Winder Stair Turns

Stairway Lighting requirements (C) Carson Dunlop

Stairway winders As the sketch, courtesy Carson Dunlop, shows, only one set of winders should be allowed in a staircase, and the dimensions shown address tripping hazards.

This sketch shows the minimum tread width and radius for curving stair treads such as the stairs in our photograph above.

In our sketch below you can see that a 90 degree turn is effected by three sequential triangular stair treads. Walking near the inside corner of this turn is difficult because of the irregular and small step area. At right are stairs that make a 90 degree turn accomplished over the rise of the entire stairway. In either case, there is no intermediate landing.

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. Also see Building Safety Hazards Guide. Here we include references to key documents on building codes and stair and railing safety.

In sum, stairway winders or turns involve triangular treads to complete the turn as you can see in our photo at right (note the handrail which is not grasp-able and not child safe).

As the sketch above left shows, courtesy Carson Dunlop, in a staircase that actually makes a 90 deg. turn (as opposed to the curved stair at right) only one set of winders should be allowed in a staircase, and the dimensions shown address tripping hazards.

Photos of Unsafe Winder or Angled Steps & Stairs

Of course more turns may be involved in a stairway, such as a circular stair. Our photos below illustrate two very steep winding attic access stairways. At below left, storing items on the stairs is of course another trip/fall hazard, while at below right you will note that the vertical stair ascent is so steep as to nearly comprise a ladder - a difficult stair to negotiate, exacerbated by the absence of any grab rail.

Bad attic access - clutter (C) Daniel Friedman

Narrow turning attic access stair (C) D Friedman

Angled Stairs Trip & Fall Hazards

Angled stairs in Manhattan (C) Daniel Friedman

Our stair photo at shows tricky angled stairs that were squeezed onto a sidewalk in New York City. A passerby agreed to model the risk of falling.

In our OPINION the crypto-trip hazard at angled stairs such as these is the fact that the stair treads and noses are not parallel to the direction of travel. This hazard is similar to circular or winder stair hazards but without the too-small tread walking area.

But walking down these stairs in the direction guided by the handrail requires the user to step on stair tread noses that are on an angle to the direction of travel, inviting a twisted foot or ankle or possibly a fall.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.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:
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Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
Eric Galow, Galow Homes, Lagrangeville, NY. Mr. Galow can be reached by email: ericgalow@gmail.com or by telephone: 914-474-6613. Mr. Galow specializes in residential construction including both new homes and repairs, renovations, and additions.
[3] "The Elimination of Unsafe Guardrails, a Progress Report," Elliott O. Stephenson, Building Standards, March-April 1993
[4] "Are Functional Handrails Within Our Grasp" Jake Pauls, Building Standards, January-February 1991
[5] Access Ramp building codes:
- UBC 1003.3.4.3
- BOCA 1016.3
- ADA 4.8.2
- IBC 1010.2
[6] 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
[7] The Circular Staircase, Mary Roberts Rinehart
[8] Construction Drawings and Details, Rosemary Kilmer
[9] 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. "
[10] Mobile Home Inspections common defects unique to factory built housing, inspection methods
[11] 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
[12] 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 sales@lawyersandjudges.com and also from the InspectAPedia Bookstore (Amazon.com)
[13] Slips, Trips, Missteps and Their Consequences, Gary M. Bakken, H. Harvey Cohen, Jon R. Abele, Alvin S. Hyde, Cindy A. LaRue, Lawyers and Judges Publishing; ISBN-10: 1933264012 ISBN-13: 978-1933264011
[14] 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 ] -
[15] How to Clean Moldy Wood Framing & Sheathing How to clean/seal mold from/on exposed lumber or plywood subfloor or roof sheathing indoors - some suggestions based on our field and laboratory research
[16] 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.
[17] Steps and Stairways, Cleo Baldon & Ib Melchior, Rizzoli, 1989.
[18] The Staircase, Ann Rinaldi
[19] Common Sense Stairbuilding and Handrailing, Fred T. Hodgson
[20] The Art of Staircases, Pilar Chueca
[21] Building Stairs, by pros for pros, Andy Engel
[22] A Simplified Guide to Custom Stairbuilding, George R. Christina
[23] Basic Stairbuilding, Scott Schuttner
[24] The Staircase (two volumes), John Templar, Cambridge: the MIT Press, 1992
[25] The Staircase: History and Theories, John Templar, MIT Press 1995
[26] Steps and Stairways, Cleo Baldon & Ib Melchior, Rizzoli, 1989.
[27] "The Dimensions of Stairs", J. M. Fitch et al., Scientific American, October 1974.
[28] Stair & Walkway Standards for Slipperiness or Coefficient of Friction (COF) or Static Coefficient of Friction (SCOF)
- ANSI A1264.2
- ANSI B101
- 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)
[29] 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
[30] 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)
[31] 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
[32] 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
[33] 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.
[34] Jinjin Li, Yuhong Liu, Jianbin Luo, Pengxiao Liu, and Chenhui Zhang, "Excellent Lubricating Behavior of Brasenia schreberi Mucilage" Langmuir 2012 28 (20), 7797-7802
[35] 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
[36] "Coefficients of Friction for Ice", The Physics Factbook™, Glenn Elert, Ed., retrieved 8/29/12, original source: http://hypertextbook.com/facts/2004/GennaAbleman.shtml
[37] "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.
[38] Serway Physics for Scientists and Engineers 4th edition (p. 126.)
[39] "How Slippery Is It", retrieved 8/29/12, original source http://www.icebike.org/Articles/howslippery.htm
[40] 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.
[41] 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 ]
[42] 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
[43] 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]
[44] 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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