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FctryRep 11-15-2012 12:42 PM

Slip Resistance of Ceramic Tile
New DCOF Standard in ANSI

Perhaps this topic has already been posted, if so I apologize. The 2012 version of the ANSI standard for tile includes a new concept for coefficient of friction that is worth knowing about for anyone that deals with tile installations in wet areas.

For years, manufacturers have published COF results as an indicator of how slip resistant a tile is. Typically they read something like "Wet COF 0.6, Dry COF 0.8" somewhere in the technical characteristics of a tile. Also for years, the tile industry has used the 0.6 wet COF number when selecting tiles for commercial or residential wet applications. This threshold has been called "ADA compliant" or "Commercial" even though there really wasn't any official standard anywhere. The ADA did at one point publish a 0.6 suggested wet COF number but never said how it should be tested (there are dozens of different ways that give completely different numbers) and it was retracted in 2004.

The numbers above are what are called Static Coefficient of Friction number (SCOF). They are measured with a tile industry test that uses a 50 lb weight sitting on some shoe sole material. The amount of force required to start the assembly moving is measured, and the ratio of the force to move the assembly over the weight of the assembly is the coefficient of friction. It is not a very reproducible number, different operators get very different results. But, it was the best we had for decades, so we used the test.

Starting about 10 years ago, but really in earnest the last 5 years, the tile industry has been working on a better test. The Dynamic Coefficient of Friction (DCOF) test measures the amount of resistance a square of shoe sole material encounters as it moves across the tile surface (or really the surface of any flooring material). This better replicates what is going on when you walk across a floor, and there is an automated device called the BOT 3000 that gives a quick and easy measurement of this force. This measurement is called the DCOF Acutest and is now part of the ANSI standard.

In 2012, the industry voted to begin using the new DCOF test for measuring coefficient of friction. Instead of 0.6 SCOF, the new threshold for DCOF is 0.42 for tiles that will be used in areas expected to be walked upon wet. While you can't directly compare DCOF and SCOF results, a rule of thumb is that a 0.6 SCOF tile is around 0.38 DCOF, so there is a small safety margin built into the new requirement. An area expected to be walked upon when wet can be the entryway to a mall or the entryway to a house, anywhere that the tile is likely to have water present when people are walking on it should meet this threshold. Manufacturers have started reporting the DCOF value and at the end of next year will stop reporting the old SCOF value.

The takeaway here is if you are used to looking for the 0.6 wet COF value, start looking for the 0.42 wet DCOF Acutest value. Most tile magazines have had articles on this topic and it has been widely presented at Coverings and other trade shows.

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