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# Understanding Dynamic Coefficient of Friction (DCOF) – Updated (2022)

Floor slip resistance is an important safety measure that all tile specifiers must be aware of when specifying flooring materials. We are concerned about slip resistance in areas where ceramic tile floors can become slippery in both residential and commercial applications. The measurement that relates to traction and slipperiness on wet, level floors when walked upon is called the dynamic coefficient of friction (DCOF). DCOF testing helps determine the likelihood of whether or not a tile surface could contribute to someone slipping or falling. When it comes to choosing the right tile for an area, DCOF is a major consideration, especially when selecting tiles for areas that may be subjected to water, oil, or grease exposure.

If you are confused about the DCOF, you’re not alone. This measurement evokes questions about the methods for measuring it, what a DCOF measurement actually means, how to compare DCOF values and what the DCOF requirements are. DCOF is now the primary product performance measure used by the North American tile industry, so it’s important to understand what it actually means.

### A Short History of DCOF

Prior to 2012, slip resistance, or the coefficient of friction for ceramic tile, was tested using the method specified in ASTM C1028, which provided the Static Coefficient of Friction (SCOF). But a new and better method for determining COF emerged, allowing project specifiers to choose the right tile for the job more easily. The new measurement, developed by the Tile Council of North America (TCNA), is referred to as Dynamic Coefficient of Friction or DCOF.

### What’s the difference between SCOF and DCOF test methods?

While the old test method determined the static coefficient of friction or SCOF, the new testing standard determines the dynamic coefficient of friction. In the context of people walking on floors, static friction is the frictional resistance one pushes against when starting in motion. Dynamic friction, on the other hand, is the frictional resistance one pushes against when already in motion. With both types of friction, a slip can occur when you push with more force than the surface can resist. The DCOF test relates better to slips occurring while a person is walking.  Additionally, the newer test method uses a slightly soapy solution (water with .05% Sodium Lauryl Sulfate, or SLS) that is more slippery than the de-ionized water used with the old test.

### What is the required minimum DCOF value?

The American National Standard Test Method for Measuring Dynamic Coefficient of Friction of Hard Surface Flooring Materials, ANSI A326.3, requires tile flooring products to have a DCOF of  0.42 or greater if recommended for use in a level interior space intended to be walked upon when wet. Keep in mind that not all tiles with a wet DCOF of 0.42 or greater are necessarily suitable for all projects and that this is a minimum level of slip resistance for level interior floors that are wet with water. Other situations, such as standing water, oil, grease, or other slippery substances, may require higher DCOF numbers. Specifiers must also consider the type of use, traffic, expected contaminants, expected maintenance, expected wear, and manufacturer’s guidelines. The ANSI A326.3 standard for measuring the DCOF is now the only ANSI standard for measuring floor traction.

In addition to describing DCOF test methods of hard surface flooring materials in the laboratory and in the field, the ANSI A326.3 standard includes DCOF specifications, product use classifications*, and guidance on specifying hard surface flooring materials. This standard is intended to serve as a guide to the general public, manufacturers, distributors, specifiers, architects, contractors, testing laboratories, building owners, and other businesses and professionals.

*Earlier this year, the TCNA announced the addition of a five-category “product use classification system” in ANSI A326.3. For the first time in the tile industry’s history, the TNCA, in collaboration with the American National Standards Institute, now requires tile manufacturers (as well as other hard surface flooring manufacturers) to provide “product use classifications” based on the properties of slip resistance.

GIO Architectural Tile + Stone is committed to the simplification of tile and stone specifications. Our products are marked with DCOF ratings presented in a clear fashion so you can easily identify the technical characteristics you require.

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