Slip Resistance of Ceramic Tiles

What is Slip Resistance?

Of all the characteristics of premium porcelain tile, the one that causes the most confusion by far is that of slip resistance. There are a number of reasons for this:

1. Consumers, and indeed many builders and architects, do not realise that ceramic tiles which have had their slip resistance tested are awarded a grade, score or rating. In the absence of this knowledge, it is therefore presumed by many people that a floor tile is simply either anti-slip or not, when in reality this is not a binary situation. Different tiles have different degrees of resistance, and this will be reflected in their rating. From that perspective, there is no such thing as an “anti-slip” tile, as every tile will fall into one of the rating categories.

2. While most other properties of a ceramic floor tile, such as abrasion resistance or strength, have an internationally agreed upon method of testing, none exist with regards to slip resistance. All that does exist are national standards, and within the EU, some guidelines. This has resulted in different countries using different rating scales from each other, and the testing procedures themselves bear little similarity to each other. The results from one set of tests do not correlate directly with those from another.

This might seem like an easy problem to solve. However, it's complicated somewhat by representatives of other flooring industries, such as wood or vinyl, weighing in to any discussions with their own concerns and opinions, in an attempt to homogenise all building regulations.

And of course, the number and nature of accidents involving slipping mean this is a much more important and widespread area of concern than the likes of chemical resistance, for example. This makes it even more difficult to achieve consensus. To date, there is no single, universal, and internationally accepted slip resistance test.

3. The terms “anti - slip”, or “slip resistance”, can be quite subjective.

There is, for starters, a difference between actual slipperiness, and perceived slipperiness. A consumer or member of the public will modify their behaviour, for example, walking up an incline, or downwards on a wet surface.

If a floor is continuously wet, it could be argued that a dry test rating is rather meaningless.

A floor that is almost always exposed to dirt, abrasive material or other contaminants will perform differently in real life to its rating (which was assigned when tested perfectly clean) would suggest.

There are other variables that interact with each other to determine whether a surface is “safe” or not. The speed of an individual walking or running; whether footwear is likely to be involved; the material from which the sole of any footwear might be made; whether a person is likely to be applying lateral pressure whilst turning.

All told, the situation is quite the mess, despite decades of discussions between various flooring industries. Depending on what country a tile is being installed in, it’s important to understand which guidelines to adhere to. Anyone specifying or considering a floor tile for a certain application should be well informed, and should err on the side of caution. Most countries have health executive arms of government which will stipulate the relevant guidelines.

The Tests for Slip Resistant Floor Tiles

The main slip resistance tests that are carried out on floor tiles are the ramp test and the pendulum test, which we discuss below. Other tests include the tortus test, a micro-roughness test, and a sled test. In the interest of practicality, we shall only touch on the tests that are by far the most prevalent in the ceramic flooring industry.

The Ramp Test

This is by far the most common slip resistance test performed. The majority of European ceramic tile manufacturers are based in Spain and Italy. The slip resistance test that most of them prefer is the ramp test. One of the advantages of this test is that, described in conjunction with it, there's a distinct list of recommended applications that relate to each resistance score. This in turn leads to architects and other tile specifiers within the construction industry to favour the ramp test.

The method itself involves a subject walking across the tiles under scrutiny, which are in turn fixed to an adjustable ramp. The subject wears specified safety footwear, and the surface of the tiles are covered in an oil. The angle of the ramp is increased until the subject can no longer maintain balance, and at this point the angle of the ramp is recorded.

The steeper the angle, the higher the slip resistance, and the higher the score. The tile is awarded an “R – rating” between 9 and 13 inclusive, with the higher rating indicative of higher resistance. There is a table at the bottom of this article showing possible suggested applications for tiles in each rating. Note that the lowest score possible is 9.

One of the disadvantages of this procedure over any other is that it needs to be carried out in a laboratory. Often situations arise, perhaps where there's been an accident or a claim, where measurements need to be taken after installation. Clearly this ramp test is of no benefit in these circumstances.

The small number of different scores is often criticised as a weakness, with each rating covering a relatively wide spectrum of resistance. Also, it’s maintained that the controlled laboratory environment can be very different to that in which tiles may eventually be installed, and thus the results may be somewhat misleading. It’s also an expensive test to carry out. Having said that, the ramp test results are extremely consistent and are therefore very reliable.