Dal-Tile Recommends Situation-Specific Minimum DCOF AcuTest Values

We have pointed out before that the ANSI A137.1 “DCOF AcuTest” and ANSI A326.3 minimum recommended wet dynamic coefficient of friction (DCOF) for level wet indoor areas of 0.42 is “one size fits all” and does not consider the use of the flooring — upstairs elevator lobby, commercial kitchen, pool deck, etc. The traction demands of different situations can vary widely.

Well-known U.S. tile manufacturer Dal-Tile recommends some additional DCOF slip rating minimums. These are not standards, as Dal-Tile points out, but it’s refreshing to see some recommendations. They go as high as ≥0.65 for ramps and stairs. For oily, greasy wet areas the suggestion is ≥0.60. This is also the suggested minimum for swimming pool decks, public showers, and locker rooms.

We take issue with the 0.42 minimum itself (which is in the ANSI standard). This was based partly on getting rough agreement with results of the obsolete ASTM C1028 static coefficient of friction (SCOF) and the traditional minimum of 0.60 static for level surfaces. It was not based primarily on safety research. What was based on human walking studies is the 0.43 minimum in ANSI B101.3. (B101.3 states a minimum of greater than 0.42, which of course means 0.43 or higher.)

The ANSI A137.1 slip test was “based on” the B101.3 test method, but the A137.1 method has some major differences that make it easier to “pass”. One main difference in the two tile slip test methods is that the amount of wetting agent (sodium lauryl sulfate, or “SLS”) in ANSI A137.1 is half that in B101.3. We would expect that this would cause a difference in the measured DCOF.

Based on a meager 8 data points on diverse surfaces, we found that ANSI B101.3 DCOF was on average 0.06 lower (range: 0.03–0.07) than the ANSI A137.1 DCOF. Although more data points are needed for a meaningful conclusion, this would imply at least that the ANSI A137.1 minimum for a level floor should be 0.43 + 0.07 = 0.50, rather than 0.42, in order to benefit from the walking studies that went into the B101.3 safety minimum. Better safe than sorry.

Our recommendation is to use pendulum testing to supplement the ANSI A137.1 slip rating test and adapt it to specific situations using detailed standards for wet Pendulum Test Value (PTV). This is discussed in an article in The Construction Specifier magazine. The main reasons are (1) the PTV standards are much more detailed, (2) they are supported by a respected consensus standard-setting body, and (3) they have been in use essentially unchanged since 1999 and were reaffirmed after 15 years of use.

Safety Direct America can conduct all the DCOF slip resistance tests discussed above. A combination of DCOF AcuTest and a pendulum DCOF test on a single sample costs $387.00 total and turnaround is usually less than three business days. Being able to show that flooring had good results in both tests can be a significant help in litigation.

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