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29 April 2014

Excuse me, but your slip is showing!

I don't know how this issue has escaped me for nearly forty years, but I'm not alone. In that time, I have occasionally talked about coefficient of friction for floors, but I just discovered there has been no widely accepted standard for slip resistance. Not only that, but neither the IBC nor ADA define slip resistance, even though both require slip resistant floors and walkways.

How the heck is that possible? Think of all the very specific requirements in the building code. How did they miss this one? And think of ADA, with its Byzantine combination of Spock-like precision in some areas, and a "Take a guess and we'll see you in court" approach to other requirements. How can it be that the good folks who write the ADA requirements know exactly what so many dimensions must be, but they have no idea what they mean by slip-resistant? It seems to me that not falling on your arse is a lot more important than a quarter inch difference in the location of a water closet, but this apparently - no, this obviously important performance characteristic has had no definition.
The IBC, in 1003.4, requires that "Walking surfaces of the means of egress shall have a slip-resistant surface and be securely attached" but does not define what slip resistance is. Apparently, the IBC doesn't care about floors not in an egress path.

According to the US Access Guide:
Accessible surfaces must be slip resistant ... However, the standards do not specify a minimum level of slip resistance … because a consensus method for rating slip resistance remains elusive. While different measurement devices and protocols have been developed … a widely accepted method has not emerged. Compliance with the standards requires specifying surface materials, textures, or finishes that prevent or minimize slipperiness under the conditions likely to be found on the surface. Standard practices for minimizing floor or ground slipperiness will likely satisfy compliance with the standards … [my emphasis].
Makes you feel all warm and fuzzy, doesn't it?

It's not that there are no standards related to slip resistance. We have:
  • ASTM C1028 Standard Test Method for Determining the Static Coefficient of Friction of Ceramic Tile and Other Like Surfaces by the Horizontal Dynamometer Pull-Meter Method.
  • ASTM D2047 Standard Test Method for Static Coefficient of Friction of Polish-Coated Floor Surfaces as Measured by the James Machine
  • ASTM D5859 Standard Test Method for Determining the Traction of Footwear on Painted Surfaces Using the Variable Incidence Tester.
  • ASTM F462 Standard Consumer Safety Specification for Slip-Resistant Bathing Facilities.
  • ASTM F489 Standard Test Method for Using a James Machine (measures slip resistance). Withdrawn 2005.
  • ASTM F609. Standard Test Method for Using a Horizontal Pull Slipmeter.
  • ASTM F695 Standard Practice for Ranking of Test Data Obtained for Measurement of Slip Resistance of Footwear Sole, Heel, and Related Materials.
  • ASTM F802 Standard Guide for Selection of Certain Walkway Surfaces When Considering Footwear Traction. Withdrawn 2012.
  • ASTM F1679 Standard Test Method for Using a Variable Incidence Tribometer. Withdrawn 2006.
  • ASTM F1637 Standard Practice for Safe Walking Surfaces.
  • UL410 Slip Resistance of Floor Surface Materials (similar to ASTM D2047).
  • NFSI/ANSI B101.1 Test Method for Measuring Wet SCOF of Common Hard-Surface Floor Materials.
Surely, with all those standards - and there are many more! - determining what slip-resistance means should be easy. Well, not quite. As noted, some of the standards have been withdrawn, and, with a couple of exceptions, most are test methods or discussions of slip resistance only that do not set minimum standards.

To make things more interesting, there is strong disagreement about the validity of various test methods and equipment. For example, the Ceramic Tile Institute of America (CTIOA) objects to the use of ASTM C1028, claiming it is "widely recognized as being inappropriate for assessing pedestrian safety" and that it "can give 'safe' ratings to very slippery materials." CTIOA and others argue that ASTM C1028, which measures static coefficient of friction, has little to do with real-world slip resistance. Furthermore, the ASTM C1028 test method is limited to the laboratory, which makes it useless for testing in-place conditions.

Some of the standards specify a coefficient of friction, but do not indicate if it is for wet or dry conditions, or do not specify the test method. Given the different materials and methods used for testing, those standards mean nothing. An additional complication is inherent in the nature of the products: we walk on them, so normal wear reduces their slip resistance. Unless there is a maintenance program to replace flooring as the coefficient of friction changes, does it make sense to specify a property that may be valid only for a couple of years?

Another contentious issue is the test condition; most tests are done dry. Even if a test is performed under wet conditions, there is little agreement about what those conditions should be. How wet is wet? Should the tests be performed with deionized water? Or with a soap solution? What about oil? Or, for that matter, banana peels?

The test methods themselves present more variables; the flooring itself is only one of the materials used in a test. Many of the older tests use leather, presumably because that was a common material for shoe soles. Being a natural material, leather is not consistent from one sample to the next. Today, many shoes use something other than leather for soles, and it's likely that the coefficients of friction vary from one material to another. It is clear that no single test will be applicable in all situations, or that it will accurately replicate even one real-world condition.

One of the more recent standards is ANSI B101, which is unique in its extent. Much more than a test method, it includes a discussion of slip-and-fall dynamics and factors that affect slip resistance of all walkway surfaces. It sets three traction levels: High, with a static coefficient of friction (SCOF) greater than 0.6, Moderate, at 0.40 to 0.60, and Low, at less than 0.40.

It doesn't look like this issue will be resolved anytime soon. Perhaps it's just too slippery.


  1. And you can add ASTM E303 - 93(2013) 'Standard Test Method for Measuring Surface Frictional Properties Using the British Pendulum Tester' which is what the ASTM F2772 'Indoor Sports Flooring Standard' references

  2. Funny you should mention that; we just had a lunch & learn about sports flooring.

  3. Sheldon, don't feel so bad. I just came to this same realization myself. You would think that after 30+ years in the profession I would have known that the COF for floors was just a rule of thumb. Maybe that's why it's called "practicing" architecture. I still don't have it right!

    I ran across this issue when one of our interior designers asked me where to find documentation on the required COF because she was having a debate about it with a client relative to a specific application on their project. After scouring the building code, ADAAG, ANSI A117.1, TCNA, MasterSpec supporting documents, and other related information, I was surprised to find that there in fact is no requirement.

    If you had discovered and posted your find a couple of months ago you would have saved me a lot of frustration! But perhaps your post will save someone else the effort. Thanks for a succinct, yet thorough, summary of the issue.

    1. This one was frustrating.When I started, I thought I would be able to get to a useful conclusion, but the more I read and the more people I talked with, the worse it got.

  4. howard i. littman - forensic architect29 April, 2014 20:04

    Sheldon, don't overlooking the 'tested by means of tandem team 3-year-old 14-hand Draft horses pulling a loaded 240-bushel corn sled' standard. It is as useful as others listed.

    This is what keeps the game interesting. The standard is the one the court agrees with after litigation comprising testimony of opposing flooring experts. It's anybody's guess.

  5. Sheldon, Another great article.. BTW here they go again ASTM C 1028(Withdrawn 2014). Watch you specs. Current Masterspec includes reference to ASTMC1028 in the "Tiling" section and i believe some Masterspec documents.

    ASTM C1028-07e1 Standard Test Method for Determining the Static Coefficient of Friction of Ceramic Tile and Other Like Surfaces by the Horizontal Dynamometer Pull-Meter Method (Withdrawn 2014) WITHDRAWN, NO REPLACEMENT

    Justin Lane, Conspectus inc.

    1. Thanks for the update, Justin. We need someone like Jim Hojnacki (Hojo) again. He published a monthly column titled "ASTM Standards That are Modified", in which he summarized many of the changes related to construction.

  6. Sheldon - You should do an article for the Specifier on this subject.
    Bob Johnson

  7. ASTM C1028 was withdrawn, but is still supported by the Marble Institute of America. The ASTM C1028 committee is now controlled by the Tile Council of North America staff which is why the TCNA withdrew ASTM C1028 and is promoting the DCOF Acutest which is now recognized by ANSI A137.1 Section 9.6 along with page 5 in the 2013 & 2014 TCNA Handbook for Ceramic, Glass & Stone Tile Installation. I am sure you already know this history. I did author and article on Coefficient of Friction published in the Spring 2104 Issue in Proinstaller. Greg Mowat

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  9. Louis Medcalf28 May, 2014 07:55

    Thanks for the excellent info, Sheldon! Slip resistance is also complicated by factors outside the control of designers, namely choice of footwear. The higher and smaller contact surface of the heel, the more vulnerable the wearer is to slipping and tripping. See "Are Clothes Modern?" by architect Bernard Rudofsky for a detailed analysis of the practical and spiritual implications of wearing high-heel shoes.

  10. Great info Sheldon, I am so glad we don't suffer the same confusion "Downunder". Here I use a ASM825 for on the fly comparisons in domestic settings, but if the client is commercial or Industrial and is looking to improve or meet his "duty of care" compliance particularly with water contamination then we always deffer to the British Pendulum to meet our AS4568 2013 Slip Resistance standards.

    Having said that however even the Pendulum struggles with textured surfaces and is of course subject to operator setup variables like a "big night" out with the boys of the late Friday test:)

    I would also like to apologize for my overzealous SEO for the comment on the 22nd

  11. Very timely for us - we were prepared for a project using ASTM C1028. Can anyone recommend a coating with minimal effect on appearance (color) other than lowering the gloss for porcelain floor tile? And thank you for being so thorough.

    1. Many years ago I saw a demonstration of an anti-slip treatment; unfortunately, I don't remember the name of the product. The amazing thing was that the ceramic tile with the treatment had greater slip resistance when wet than it did when dry! A few years ago I asked several tile reps if they knew of any treatments. One I remember is Slip Tech, but there are others. I have had no experience with any of them, so I can't recommend any.

  12. Hi Mitch, we have had good results with a product from Anti Slip Protection USA. It is a surface coating however the developer claims it will hold the SCOF for 3 years in light commercial environments. IWe have some job completed job images here

  13. Our passion for this business grows out of the fact that slip-and-fall injuries can be devastating, life-changing events, particularly for our older and most vulnerable citizens. Slip Doctors has developed several methods for improving traction on tiles, stone, VCT, porcelain, concrete, ceramic, acrylic, fiberglass and most other surfaces commonly found on walking surfaces, boat decks, porcelain and fiberglass bathtubs, showers, wood – even synthetic surfaces. The application of our products non slip, anti slip floor treatment, non slip flooring, non slip floor treatment and slippery floors are easy and will result in marked improvement in surface traction.