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Slip resistance can be tricky to evaluate. Because there are numerous factors that can affect the slip resistance of a surface, properly evaluating it requires the right testing methods, controlled testing environments, numerous tries and of course, a standard rating by which slip resistance can be measured.

Naturally due to the many factors that affect slip resistance and the different test methods available today, there are also a number of different slip resistance ratings in existence. To get a better grasp of what these ratings are, where they apply and what they signify, we’re breaking them down to the basics.

Australian Slip Resistance Ratings

Current slip resistance testing in Sydney and throughout Australia can be very broadly classified into two: the testing of new pedestrian surfaces and of existing pedestrian surfaces. Slip resistance testing of new pedestrian surfaces is done in accordance with AS 4586, which is the most current National Association of Testing Authorities (NATA) approved slip resistance rating; while slip resistance testing of existing pedestrian surfaces is done in accordance with AS 4663.

When determining the slip resistance of new pedestrian surfaces, there are also two major classifications of slip resistance test methods. There are methods for measuring slip resistance in dry conditions, and for measuring it in wet conditions. When measuring slip resistance of dry surfaces, a floor friction tester is used, whereas wet surfaces can be tested through a Wet Pendulum Test, Wet Barefoot Ramp and Oil Wet Ramp.

Slip ratings can be categorised in the following manner:

  • R ratings are for the oil wet ramp test
  • P ratings are for the wet pendulum slip test
  • D ratings are for the dry Floor Friction Test
  • A, B & C ratings are for the wet barefoot ramp test

What Do All These Letters Signify?

As you can see, slip resistance ratings involve more than just a few letters, not to mention those that you’ll see on flooring materials like tiles. Floor tile slip resistance ratings can often be readily seen on tile boxes; letters like DS and NPD. What is slip resistance rating DS and NPD? What do all these letters mean?

First, let us take a look at the measurement of dry slip resistance. This is measured using a Floor Friction Tester or FFT, also popularly known as the Tortus. It is a portable, self-powered device which measures the dynamic coefficient of friction between the surface and a standard rubber slider as it moves across the surface.

If the coefficient of friction is greater than or equal to 0.4 this is classified as class D0, and if the coefficient of friction is measured at less than 0.4 this is classified as class D1 and must be improved to achieve a D0.

With the Wet Pendulum Test, there are two sets of standards corresponding to the two types of rubber sliders that can be attached to the Pendulum Friction Tester. Slider 96 is often used for testing polished to moderately textured surfaces, whereas the Slider 55 is used to test more coarsely textured surfaces. Slider 96 is relatively harder and simulates a standard shoe sole, while Slider 55 is made of a softer rubber compound much like tyre rubber, and can be used to simulate soft rubber shoe soles or even bare feet.

The slip rating from the Wet Pendulum Test is derived from a minimum of five specimens tested, and the average of these five values then becomes the Slip Resistance Value or SRV. The classification then is as follows: