COF (Coefficient of Friction) is a numeric value that represents the amount of friction between two objects.
DCOF (Dynamic Coefficient of Friction) specifically tests the friction of an object that is already in motion (kinetic).
SCOF (Static Coefficient of Friction) specifically tests the friction of an object that is moved from a standing position (break away point).
The BOT-3000 (Binary Output Tribometer) is a machine about the size of a shoe box that runs approximately 8” across a surface, measures the DCOF of the tile and provides a digital reading with the results. Because the machine is automated it is able to objectively measure the slip resistance and most importantly provide repeatable results. A BOT3000 can also measure SCOF and comes with various sensors (neolite, rubber, etc.) for various surfaces and surface conditions. The BOT3000 is endorsed by the National Floor Safety Institute and is ANSI compliant.
ASTM C1028 is a method used to measure SCOF. This method was withdrawn as a recommendation a number of years ago as some of the results could be skewed due to human error. The method involved a 50lb. weight being placed on a sled that was then pulled across a surface by using a force spring. The spring balance is connected to the sled and the force is increased until the block begins to move. The reading on the spring balance scale when the load begins to slide is a measure for the static friction. Different individuals conducting this test could potentially yield different results. The tile industry continued using this method simply because there was no new standard to replace it.
We highly recommend that a reputable lab or a trained certified user conduct DCOF testing. The test is very specific according to ANSI standards and requires that the following parameters be met to ensure consistency and accuracy between tests and also between users:
There are currently no mandatory requirements by either organization. The most up to date recommendation is the ANSI A137.1-2012 Version 1 Section 220.127.116.11.10.
OSHA RECOMMENDATION- OSHA does not have any standards that mandate a particular COF for walking/working surfaces. While there are devices to measure the COF, no OSHA standard specifically requires that employers use or have them. The non-mandatory appendix (Appendix A to Subpart D), in the Notice of Proposed Rulemaking for Walking Working Surfaces for general industry, discusses COF and states (at section A4.5) the following: "The Occupational Safety and Health Administration recommends that walking surfaces have a static coefficient of friction of 0.5 SCOF.”
ADA RECOMMENDATION- According to the 2003 edition of ADA advisory on surface conditions; The ADA's position on slip resistance is that a surface must be “firm, stable and slip resistant”. In 2003 the ADA had also retracted its guideline number s of .60 on horizontal surfaces and .80 on ramps. The reason for their retraction was that the tile industry lacked a standard testing method. The previous representation of the ADA .60 SCOF guideline is NOT a current standard for specifiers. Should an architect or designer seek to specify a surface as “slip resistant” they must follow the new ANSI guidelines (ANSI A137.1-2012 Section 18.104.22.168.10).
TCNA/ANSI RECOMMENDATION- In March 2012 TCNA/ANSI completed and passed the first ever industry standard for measuring COF with a minimum threshold value, called the ANSI 137.1 2012 DCOF Standard. This new industry standard defines a method (BOT3000) and a measure (≥.42) for wet DCOF testing.
NO. ANSI A137.1 Section 22.214.171.124.10 specifically says:
“COF shall not be the only factor in determining the appropriateness of a tile for a particular application.”
“The specifier shall determine tiles appropriate for specific project conditions, considering by way of example, but not limitation, type of use, traffic, expected contaminants, expected maintenance, expected wear and manufacturers’ guidelines and recommendations.”
“Tiles with a wet DCOF of <.42 (including by way of example, but not in limitation, polished tiles, shall only be installed when the surface will be kept dry when walked upon and proper safety procedures will be followed when cleaning the tiles.”
You cannot compare the numeric values of SCOF and DCOF side by side because they are two completely different test methods that yield completely different results. However, when testing the same tile with both methods, a .38DCOF wet result was closest to a .60SCOF wet result.
NO. COF ratings are only meant to show a relative comparison between products. A benchmark of ≥.42 was set to identify what is considered “slip resistant” but the results are not meant to identify if a product will be “slip proof”.
YES. The DCOF of installed tiles can change over time as a result of wear, surface contaminants and cleaners. Surfaces should be cleaned regularly and deep cleaned periodically. Traction-Enhancing maintenance may be needed periodically to maintain DCOF values in commercial applications.
According to ANSI A137.1-2012 Version1 Section 126.96.36.199.10, there are many factors that affect the possibility of a slip occurring on a tile surface including by way of example, but not in limitation, the following: