Coefficient of friction (COF) is a measurement of how slip-resistant a floor surface is, expressed as a number that compares the force needed to slide an object across the floor to the force pressing it down.
Understanding Coefficient of Friction in Flooring
Coefficient of friction, often shortened to COF, is the measurement used to describe how likely a floor surface is to cause a slip. It is expressed as a ratio between the horizontal force needed to move an object across a surface and the vertical force pressing that object down. A higher number means more traction, and a lower number means a slicker, higher-risk surface.
Static vs. Dynamic COF
Static coefficient of friction measures resistance to the start of movement, while dynamic coefficient of friction measures resistance once an object is already sliding. Most modern testing standards, including the ANSI A326.3 test method used in the flooring industry, focus on the dynamic value since it better reflects real-world walking conditions, especially on wet surfaces.
What COF Numbers Mean for a Coating Job
A dynamic coefficient of friction at or above 0.42 is generally considered acceptable for level interior floors under the ANSI A326.3 standard, while wet or high-risk areas like commercial kitchens, pool decks, and loading docks typically call for a higher value. Contractors control COF by adding slip-resistant additives, texture, or specific aggregate broadcast rates into the top coat of a system.
Balancing Slip Resistance and Cleanability
More texture means more traction, but it also means more surface area for dirt and grime to collect, which can make a floor harder to clean. Choosing the right slip-resistant additive and broadcast rate for the specific environment, rather than defaulting to the roughest option available, keeps the floor both safe and practical to maintain.
Also Called
COF, Slip Resistance Rating
