Coefficient of Friction (COF) and “SCOF” Versus “DCOF”
The Coefficient of Friction (COF) of a tile is a measure of its “slip resistance.” For example, the dry cement patio around a public pool is very slip resistant (so it would get a high rating) and the ice on hockey rink is VERY slippery (so it would get a low rating). For tiles, it is important because ratings above a certain number comply with the Americans with Disabilities Act (ADA) and can be used in commercial areas or public areas.
Two different ratings: STATIC COF (SCOF) and DYNAMIC COF (DCOF)
SCOF: This is the force required to START something moving. If you are standing still, this is the force between your shoe and the floor to get you from stopped to moving. If you apply a LOT of force, you slip. This test shows the amount of force needed JUST BEFORE you slip. To pass ADA the test must be done on a WET tile and the result rating must be greater than 0.6.
DCOF: This is the force required when something is in motion. If you are walking, the more pressure you apply, the faster you will go. This test shows the amount of force needed just before you slip WHILE you are already in motion. To pass ADA the test must be done on WET tile and the result rating must be greater than 0.42.
As this is a rating system used only in the USA, many factories throughout the world do not test their tiles for COF. Tiles with COF ratings are harder to identify since COF certifications (or lack of) are not generally displayed with the tile. COF information is also not always immediately accessible to tile showroom salespersons without some research.
No tile is “slip-proof.” Proper maintenance is critical. Improper maintenance and maintenance products can result in a build-up on the surface of the tile causing the tile to be slippery.
Most of the largest tile manufacturers (such as Marazzi, American Olean and Crossville) offer several lines with COF certifications along with a host of matching trims such as a “cove base,” that may be required for the intended commercial application. Crossville even offers several customized surface textures (Crossdot, Cross-Grip, and Cross-Tread) which help meet specific industrial application needs such as food services. Along with appropriate footwear, prompt removal of contaminants, effective drainage, and proper maintenance, in floor applications with consistent surface presence of water, oil, or grease, ceramic and porcelain tiles (unless quarry tile) should not be used unless the tile is “treaded,” or has a special surface treatment.
In use for decades, American Olean’s quarry tile offers additional surface options such as “abrasive” and “double abrasive.” Suitable for pool deck use, quarry tile is generally found in three earthy colorways: tan, red, brown and “flashed” variations of each (American Olean) and in a vast array of decorative shapes and sizes within Arto Brick’s unglazed “Monrovia Tile” series.