Floor coefficient of friction (COF) testing is the measuring of the slip resistance of a flooring surface. The static coefficient of friction (SCOF) is the force required to start an object moving relative to the surface, divided by the weight of the object on the floor. It is a measure of the resistance to sliding of a stationary object, or rather, a measure of how slippery a floor is to someone standing still on it. Sound irrelevant? You bet! It’s absolutely irrelevant, but using SCOF test results proved to be a great way to fool unsuspecting flooring consumers into buying slippery floors for decades in the USA.

Slip and fall accident on polished floor

Slip and fall accidents happen 100% of the time when someone is walking across the floor, so dynamic coefficient of friction (DCOF) testing is needed to accurately assess a floor’s slip risk. Slip and fall accidents never happen while someone is simply standing still on a floor.

The validity of floor SCOF testing was completely debunked in the international floor slip resistance testing community many years ago, and almost all SCOF floor test methods in the USA have now been withdrawn. The rest of the world never used these irrelevant tests, and never will. In this blog post, we will discuss the irrelevance of floor SCOF testing and the reasons why almost all those old, outdated and misleading floor SCOF test methods have now been withdrawn.

Tile SCOF testing was widely used to help sell slippery flooring in the USA for many years, and the ASTM C1028 SCOF test was mostly promoted by the Tile Council of America (TCNA), as representatives of Daltile and other major American tile manufacturers, to help make Americans feel like they had some “scientific proof” that their slippery tiles and polished floors weren’t slippery. However, the reliability and validity of SCOF testing was questioned for many years by everyone who ever performed this SCOF test or witnessed the test being done.

Withdrawn ASTM C1028 SCOF Test

The ASTM C1028 SCOF floor test was finally withdrawn by the ASTM in 2014 because it was getting people killed and horribly injured by giving “passing” slip resistance ratings (0.60 or greater) to the most slippery of floors. One of the main problems with wet SCOF floor testing is that it does not take into account stiction, which is where the rubber used in the test sticks (using suction) to the most slippery of floors (polished and very slippery-when-wet floors), giving false and misleading slip test results. As a result, SCOF testing does not accurately reflect the slip resistance of a floor in real-world conditions.

NFSI/ANSI B101.1 (National Floor Safety Institute/American National Standards Institute) was published in 2009 to mimic ASTM C1028 readings. The B101.1 floor SCOF test utilized the BOT-3000E tribometer, which made the readings digital and left less room for the person doing the testing to “massage” the test to get a favorable reading for his or her client, which was just one of MANY major problems with ASTM C1028 before it was withdrawn. But NFSI/ANSI B101.1 was still measuring SCOF, which is totally irrelevant and misleading.

The B101.1 SCOF test was allowed to expire (notice the link shows it as an “historical” standard) shortly after ASTM C1028 was withdrawn because the cat now was out of the bag – SCOF testing was and is irrelevant. The manufacturer of the BOT-3000E acknowledged that SCOF testing is irrelevant and no longer endorses using SCOF testing to assess floor safety. Many years later, the NFSI re-published their own version of this horrible SCOF test – NFSI B101.1. They’ve been pushing irrelevant and dangerous floor SCOF testing nonsense for so long now that they had to keep up the charade, apparently. Members of the NFSI (with their bogus B101.1 test) and the Underwriter’s Laboratories (responsible for the highly misleading and bogus UL 410 SCOF test for “polished floors”) must be the last people on earth still pushing SCOF testing as an accurate assessment of floor slip risk. SCOF testing is dangerous. Plain and simple.

The ASM 825A SCOF Tester

The ASM 825A is another device that was created many years ago to mimic the ASTM C1028 floor SCOF test. (The name ASM was likely an attempt to sound like “ASTM”, which stands for American Society for Testing and Materials.) It allowed building owners to have their security guards or maintenance staff do SCOF tests on site with a little device costing only a few hundred bucks that they’d yank across the floor to get a SCOF reading.

Most floors were easily capable of obtaining a 0.60 or greater (even the most slippery-when-wet polished floors) using this cheap little device, which allowed building owners to pretend they were doing their due diligence by testing their floors for slip resistance regularly, which could help them from being held negligent when the slip and fall lawsuits came in. And in many cases they did come in … because SCOF testing was just providing a false sense of security. There was no verifiable science behind any of these tests or test devices.

Another test method which utilizes a combination of SCOF and something expert court liars call “slip index” was withdrawn due to concerns about its reliability and validity. The English XL tribometer (and its test method ASTM F1679), which has been widely used in USA courtrooms, was withdrawn in 2006 after OSHA and the ASTM gave up on receiving a reasonable precision statement from it’s users.

Similarly, the Brungraber Mark II slip tester (also known as the PIAST) and ASTM F1677, which has been used almost entirely in USA courtrooms to create favorable courtroom “data” for lawyers, was also withdrawn in 2006 after it was found to be highly sensitive to what kind of result the user was getting paid to get (whether he was working for a plaintiff personal injury attorney or the building owner’s defense attorney), although these “expert liars for hire” mainly specialize in testifying that slippery floors aren’t slippery. And they make a great living doing so!

The James Machine and it’s test method ASTM F489 is another floor SCOF test that was created to help fool people into a false sense of security when purchasing and maintaining very slippery floors. ASTM F489 was withdrawn years ago, but UL 410 and the vinyl flooring industry (using ASTM F2047) still use this fraudulent and flawed floor SCOF test to mislead flooring consumers. F2407 is supposed to only be for testing “polish-coated flooring surfaces”, but flooring manufacturers of all types love to ignore this fact and use this poor and unreliable SCOF test to say their slippery floor isn’t slippery.

Old James Machine SCOF Tester

The James Machine SCOF test used in UL 410, ASTM F489, and ASTM F2047 measures how slippery a floor is to someone standing still on a clean and dry floor. Can you imagine someone claiming they suffered a slip and fall accident while standing still waving to a friend on a clean and dry floor? (Try finding a lawyer to take THAT case!) To use this test to assess real-world floor slip resistance is nothing short of fraud.

You either have to be profoundly ignorant or incredibly lacking in integrity to use an SCOF test like this to say a floor is slip resistant. Slip and fall accidents happen when someone is walking across a wet or otherwise lubricated floor. Dust can be a very slippery contaminant on its own (drywall dust, especially). Therefore, reliable floor slip resistance tests must be done using DCOF test methods in contaminated conditions to determine real-world slip resistance. No floor will always be kept perfectly clean and dry, and every floor will have someone walk across it at some point. Therefore, dry SCOF test methods are completely irrelevant.

Given the problems with SCOF testing, experts with integrity agree that it is not a reliable or valid way to assess the slip resistance of a floor. Instead, they recommend using a holistic approach that takes into account all of the factors that can affect slip resistance, such as surface texture, surface contaminants, footwear, environmental conditions, and reliable DCOF testing methods. This approach may include visual inspection, regular walkway auditing, and slip resistance testing using the pendulum tester.

Pendulum Floor Slip Resistance Tester

The most widely-accepted DCOF floor slip resistance test method in the world today that has been gaining popularity in the USA in recent years is the pendulum test. The pendulum test accurately measures the coefficient of friction (COF) of a floor by swinging a weighted pendulum arm with a standardized rubber foot across the surface and measuring the distance it travels before coming to a stop. The pendulum test has been shown to be more reliable and valid than SCOF test methods and is widely used in Europe, the UK, Israel, Singapore, China, India, and Australia, to name a few countries that have been relying on pendulum test data for several decades to help stop preventable slip and fall injuries in the workplace, homes, and public places.

In fact, there are at least 50 nations around the world that have a published, peer-reviewed test method for use of the pendulum to assess the real-world slip resistance of a floor. In the USA, the test method is called ASTM E303-22, which was updated in 2022. In Europe, it’s EN 16165:2021, which was just updated in 2021. In Australia and New Zealand, they use AS 4586 (new flooring) or AS 4663 (existing floors), which was last updated in 2013.