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Slippery Stair & Walk Surface Hazards Coefficients of Friction or Slipperiness of Various Walking Surfaces       Slippery stairs or walks: Algae, Ice, Fungus, Wet Surfaces & Other Stair Slip, Trip & Fall Hazards Causes of slippery walking surfaces on exterior ramps, stairs, or walks - Photos of unsafe steps & other walking surfaces due to algae, ice, water, snow Algae on Stair Treads vs Recommended Coefficient of Friction (COF) and Static Coefficient of Friction (SCOF) Comparing the Slipperiness of Algae with that of Ice & Other Slippery Walking Surfaces Table Comparing Coefficients of Friction for Various Walking or Driving Surfaces & Materials Definitions of COF - coefficient of friction and SCOF - static coefficient of friction; Recommended coefficient of friction on walking surfaces Algae Appears on Other Building & Surrounding Surfaces: Concrete, Brick, Roofs, Siding How to Reduce the Hazard of Algae Growth on Stairs or Other Walking Surfaces Snow & (ice on Walking Surfaces - Slip Trip Fall Hazards - Building code & other standards that try to address slippery walking surfaces SLIP TRIP & FALL HAZARD LIST, STAIRS - separate article SLIPS , TRIPS & FALLS, EXTERIOR STAIRS - separate article SLIPPERY STAIRS, WALKS Questions & Answers about Algae, Ice, Fungus, Wet Surfaces & Other Stair Slip, Trip & Fall Hazards References

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This article describes and includes illustrations of common causes of slippery walking surfaces on stairs and walkways. We provide citations of recommended anti-slip or anti-skid steps or other walking surfaces, we define COF - coefficient of friction and SCOF - static coefficient of friction, and we cite recommended COF or SCOF for stairs and walkways. We provide a table that compares the slipperiness of different walking surfaces & surfaces such as dry versus wet concrete, steel or wood, and algae, snow, ice or water coated walking surfaces. We also provide some stair and walkway maintenance suggestions to reduce slip, trip and fall hazards due to water, algae, snow, ice, etc. Because a slip, trip or fall on stairs or walkways may involve more hazards than just the slipperiness of the walking surface, also see Exterior Stair Falls and STAIR TREAD DIMENSIONS and Codes for Stairs as well as other stairway construction, code, & inspection articles in the links listed at Related Topics .

Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.

Algae, Ice, Fungus, Wet Surfaces & Other Stair Slip, Trip & Fall Hazards

Daniel Friedman

Algae on steps & other walking surfaces - trip hazard Algae growth on steps or decks: green or sometimes black algae grows readily on wood, concrete, or stone surfaces in most climates, particularly where those surfaces are repeatedly wet and especially if the surface is also shaded. Algae makes these walking surfaces dangerously slippery, particularly when wet - a slip, trip and fall hazard which is widely recognized. [29][30][31][32]

The green algae-covered deck shown at left was inspected by the author who in fact nearly had a bad fall due to wet algae on the deck where the ladder was placed. You can see the scrape marks of the ladder feet (where my pen is pointing in the photo, above right) and the good luck that the ladder slippage was stopped by the chimney base. Algae, when wet, is one of the slipperiest substances known.

It is readily observed that algae growth on wood surfaces may seem harmless when the steps are dry, but when any stair surface, stone, brick, wood, or other, is covered with algae and becomes wet, the surface is extremely slippery, adding significantly to the risk of a serious fall and injury.

Also see ALGAE, FUNGUS, LICHENS, MOSS for images of algae under the microscope.

Algae on Stair Treads vs Recommended Coefficient of Friction (COF) and Static Coefficient of Friction (SCOF)

Our photo (left) illustrates that multiple hazards may combine at an individual stairway leading to a fall even by people who have used the stairs many times before. The stair we show has treads that are too narrow, rise too high, uneven step riser heights, no tread nose, and no stair handrailing. But notice that at the time of our inspection the stair tread surfaces were also wet, adding to the fall hazard.

Stair Tread Anti-Slip or Coefficient of Friction Requirement for Safe Walking Surfaces

Various industry, ANSI, ASTM, OSHA, ADA standards recommend a static coefficient of friction (SCOF) of 0.5 or higher (ADA 0.6 or above) and define surfaces with SCOF of 0.4 or lower as "low traction", i.e. "slippery". [28]

Model building codes attempt to address the effects of algae, ice, snow, and water on stairs and walkways.

But because building codes & standards cannot anticipate every possible physical cause of slipperiness on walking surfaces or stairways, codes generally do not attempt to address every possible slippery substance that might be present such as algae, ice, snow, water, even spilled oil or food or wet paint on steps.

Since building codes cannot anticipate every possible slip trip and fall hazard, instead codes and standards typically state something like the text shown below.

1009.5.2 Outdoor conditions. Outdoor stairways and outdoor approaches to stairways shall be designed so that water will not accumulate on walking surfaces. In other than occupancies in Group R-3, and occupancies in Group U that are accessory to an occupancy in Group R-3, treads, platforms and landings that are part of exterior stairways in climates subject to snow or ice shall be protected to prevent the accumulation of same. - IBC (International Building Code) [43]

or

Slippery conditions on stairways must be corrected. - OSHA standard on temporary workplace stairways [42]

1003.4 Floor surface. Walking surfaces of the means of egress shall have a slip-resistant surface and be securely attached. - ICC and as adopted by various states throughout the U.S. [44] (Similar provisions are made for ramps in 1010.7.1 and 1010.7.2)

Comparing the Slipperiness of Algae with that of Ice & Other Slippery Walking Surfaces

Algal growth (green, brown, black) on a wood walking surface such as a stair, ramp, or deck may feel and look pretty harmless when it's dry (photo at left). But when there is even a modest level of dew, or water the surface can become more slippery than teflon. Watch out: Wet algae may be in fact more slippery than ice: The COF of kinetic (moving) rubber (say a car tire) on ice is standardized at 0.15.and depending on the material contacting the ice, the COF of ice may appear as low as 0.017 - less than Teflon. [36][37] Gourdon et als. showed that algae can have a coefficient of friction (COF) as low as 0.015 - enormously slippery.[32]

How Slippery are Various Stair & Walkway Surfaces?

Table Comparing Coefficients of Friction for Various Walking or Driving Surfaces & Materials Note 1
Materials / Surface Alphabetic Order	Static Coefficient of Friction (SCOF) Friction before movement	Coefficient of Friction (COF) Sliding friction
Algae	0.015 [32]
Asphalt paving (frost covered) [39][40]		0.53 - 0.63
Asphalt paving (dry) [39][40]		0.72
Ice: Glare ice on asphalt paving Smoothest ice, similar to wet ice, water not observed (note for icy surfaces the nature of the material below is probably irrelevant in measuring friction)		0.19
Ice on asphalt paving with sun exposure, not melted [39][40] Ice, wet, on asphalt paving [39][40]		0.24
Ice on Steel	0.03	0.03
Ice on Ice	0.05 - 0.5	0.02 - 0.09
Leather on Metal (e.g. a shoe sole on a dry steel stair tread)	0.4 - 0.56
Leather on metal, wet or greased [41]	0.2
Leather on Oak (shoe sole on an oak stair tread, presumably unfinished and unpolished tread surface)	0.27 - 0.38
Masonry on Brick (a brick set on concrete)	0.60 - 0.7
Recommended Minimum SCOF for walking surfaces (OSHA etc).	0.5
Recommended Minimum SCOF for walking surfaces (ADA) [28]	0.6
Rubber on Ice (tennis shoe on icy step or car tire on icy pavement) [37]		0.15
Rubber on wet concrete [41]	0.45 - 0.75
Rubber (car tire or tennis shoe sole) on concrete (all surfaces dry, no loose sand, etc)	0.6 - 0.85 [41]	0.8 [38] - 1.02
Rubber Car tire on wet road [presumably asphalt] [41]	0.2
Rubber (tennis shoe or car tire) on dry asphalt [41]		0.9
Rubber (car tire or tennis shoe sole) on grass (presumably dry) Packed (car driven over) snow or fresh unpacked snow		0.35
Skin (bare foot) on metal surface (presumably dry)	0.8 -1.0
Snow on waxed hickory (similar to snow on a waxed or perhaps poly or painted stair tread) [28] Snow or ice on asphalt [39][40]	0.04 - 0.4	0.04 - 0.4
Snow, wet [41]	0.14
Teflon	0.04
Wood, clean [41]	0.25 - 0.5
Wood, wet [41]	0.2
Wood, waxed [41]	0.04
Notes: 1. Table adapted & expanded from "Friction", the Physics Hypertextbook, retrieved 8/29/12, original source: http://physics.info/friction/ 2. Friction measures the force between two surfaces that are in contact and measures the resistance to their slipping or tangential motion. There are two coefficients of friction, static friction (nothing is already moving) (SCOF or Us) and kinetic friction (moving or sliding) (COF or uK). The measure of friction is independent of the surface area, speed (as long as speed is more than zero), and temperature. The amount of friction depends on the nature of the surfaces in contact with one another and the force between them (such as the weight of a person whose shoe sole is in contact with a stair tread surface. The "roughness" of a surface has a minor impact on friction, and friction can be higher between smooth surfaces. 3. The Ice on Ice example in the table above illustrates the reduced amount of friction when movement is present

Algae Appears on Other Building & Surrounding Surfaces: Concrete, Brick, Roofs, Siding

Green or black stains due to algae: green stains also appear on buildings including on roof shingles, tiles, slates, on building siding, and even on masonry walls, sidewalks, planters, and retaining walls: stone, concrete block, and concrete. If you see flat green stain on a building exterior and that is not producing any plant-like raised growth it is likely to be an algae. In our photo at left both the green on the concrete grate-surround and the black on the sidewalk may be species of algae. Why are they different? Perhaps different genera/species prefer different nutrients in the two pours of concrete, or perhaps because of moisture or other surface differences.

Watch out: on walks, decks, ramps and stairs, algae makes for a dangerously slippery surface, particularly when it is wet.

At above right our photo illustrates that bricks used in a stair or walkway may be quite uneven in their ability to host slippery algal growth. Two bricks in the foreground (above the 2012) have appear to have a modest algae growth while others did not show algae. But of course there are other trip hazards here - loose bricks.

Algae under the microscope has a distinctive appearance that easily distinguishes it from moss, lichens, and mold, as we show here. This microphotograph of algae was made in our lab while examining a sample sent to us from our friend and mold lab expert Sue Flappan. The original algae sample was collected from a concrete sidewalk using simple adhesive tape.

How to Reduce the Hazard of Algae Growth on Stairs or Other Walking Surfaces

• Slippery Algae-coated stair tread hazard reduction.
  The cedar wood steps shown at left were located at a home in the northeastern U.S. in an area of shade and dampness. The presence of lichens as well as algae illustrate that even rot-resistant cedar decking and steps are not immune to these slippery conditions.
• Clean and remove algae growth. Algae on steps is often green, sometimes black in color.
  
  Algal growth can be removed from outdoor steps using a power washer with or without deck cleaners such as the products described at STONE CLEANING METHODS
  
• Do not direct roof runoff, downspouts, nor surface runoff onto stair surfaces. Such water promotes algae or fungus growth on the stair surface and in freezing climates, ice formation.
• Use anti-slip additive in paint on outdoor stair treads, landings, and entry porches, such as a fine-ground sand powder which is mixed in with the paint. Anti-slip stick-on plastic tread covers are also available.

• Masonry stair treads and entry platforms should be slightly pitched away from the riser (or away from the building for platforms) in order to drain water away from the riser side of the step - you don't need much pitch to drain, 1" in 45" of run is sufficient and won't violate building code. Good drainage on a masonry stair (or walk) also reduces damage from frost-related surface spalling and cracking. (Also see STONE CLEANING METHODS and for more algae images and data about algae on buildings see ALGAE STAINS ON ASPHALT ROOF SHINGLES)
• Masonry stairs should be protected from frost heaves by proper gravel, backfill, drainage, and other construction details
• Regular stair safety inspections performed by someone familiar with stair, railing, and safety requirements should discover hazards due to poor maintenance, stair or step or handrail deterioration, loose or worn stair treads or railings, or even bad original design that has gone unattended. The steps shown in our photograph above are improperly constructed with too-narrow treads, loose components, and a flimsy "handrail" placed too low, just 24" above the step tread surface.

More examples of exterior stair slip fall hazards are at Exterior Stair Falls and at Exterior stairs.

Ice, Snow or Even Plain Water on Steps Means Very Slippery Surfaces

Water means slippery stairs and walks, icy or not. In our table of surface slip coefficients of friction (above) we indicated that water on a walking surface significantly reduces the COF or increases the surface slip hazard. Water atop ice and "black ice" are still more slippery (lower SCOF or COF) than water alone or ice alone on most surfaces. The ice-covered exterior steps shown just below were pointed out to us by Paul Galow.   In our photo (below-left) water is running over these stone stairs, combining water, possibly thin algal coatings on some stones, and debris to add to a serious slip hazard.

At above right the author tries out stone surfaced stairs in Girona, Spain. Early morning mist left a thin wet coating that made these steps actually more treacherous than the running stone steps on the hiking trail at above left. When water is visibly running down the steps on a hiking trail the walker might expect trouble and may walk with more care than a casual stroller or worse, a runner up the Spanish steps shown at above right.

Difficult-to-maintain snow and ice fall on decks, porches, steps, walks

We liked the photo at left because it shows both green algal growth down the brick building wall and typical snow and ice conditions at a masonry walk and stair in the Northeastern U.S. Notice that in recognition that the steps will experience snow melt and then ice re-freezing during the daily temperature cycle, the site maintenance crew have left a bag of ice-melting crystals by the entry door.   In our photo at below left, even before construction had been completed we wondered about future ice hazards on the deck shown in our photo at left. Ice and snow melting and dripping off of roof eaves onto a deck or porch where the water re-freezes can lead to a surprise trip hazard.

At above right you can just make out a stone and gravel walkway along side of the building. Because shoveling snow off of combined surfaces (flat stones surrounded by gravel) can be difficult these walks may not be adequately cleared and may present a fall hazard more often than other surfaces exposed to winter and freezing weather.

Watch out: using a power snow-blower where loose gravel is present can throw a stone through a window or into an eye. The owners cleared this walk by hand but later later decided to reduce the risk and hassle of this hard-to-clear stone walkway by installing a roof over the entire walkway.

Frequently Asked Questions (FAQs) about Slippery Walking Surfaces & Stairways

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Technical Reviewers & References

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

• 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
• 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:
  • Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
  • Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
  • Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
    Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
  • The Home Reference Book, a reference & inspection report product for building owners & inspectors.
    Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
  • The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
    Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
  • The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
    Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
  • The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
• 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.
• Paul Galow - technical consultant on networking, LAN design, applications support. Galow Consulting Services, 914-204-1749, email: paulgalow@galowconsulting.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

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author. Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

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