The following summary is from the TCNA, and directely linked with the article title
Changes to coefficient of friction (COF) standards for ceramic tile
Many manufacturers have stopped reporting coefficient of friction (COF) per the C1028 method. Why? The standard for COF for ceramic tile floors has changed! And there is now a ≥0.42 requirement, measured per the DCOF AcuTestSM, for level interior tiles that will be walked on when wet.
To meet the new DCOF AcuTest criteria, you cannot use old COF values from C1028 measurements. As the methodology is different, there is no direct correlation from C1028 values to DCOF AcuTest values.
Whether you're manufacturing, specifying, selling, installing, or maintaining ceramic tile floors, it's important to know the DCOF AcuTest value. Need help? Our lab not only runs this test, we helped develop the protocol. Send us your tiles today, and be sure you're meeting this new and very important safety standard.
For an in-depth look at this issue, it is recommended that you read the TCNA Tecnical Bulletin, linked below.