Slip resistance R ratings: Can the results be trusted?

Slip resistance R ratings: Can the results be trusted?

March 2019

David Talbot from Craven Dunnill & Co Ltd considers some key issues relating to slip resistance of flooring materials.  Talbot is a TTA Technical Committee member, UKSRG Technical Committee member, and Chairman of BSI committee B539.

As the HSE document on Assessing the Slip Resistance of Flooring make clear; “Slips and trips are the most common cause of injury in the workplace and cover over a third of all major injuries and over 40% of all reported injuries to members of the public”.

The slip resistance, or coefficient of friction, of flooring materials has for many years been a greatly misunderstood subject.
Numerous test procedures are used around the world and can be put into three main categories:

  • Tribometers or Sled type
    Portable machines that effectively drag themselves
    over a surface, for example the Tortus or BOT 3000
  • Ramp Tests
    Adjustable laboratory test rigs subject to contamination with oil (DIN51130 – R ratings) or soapy water (DIN51097 – A/B/C ratings)
  • Pendulum machines


Portable test machines that replicate the action/movement of the human foot
For years some specifiers have been relying on the DIN51130 R ratings to give a guide to the slip resistance of a material: whether ceramic, wood, resilient flooring, carpet, or any other flooring material.

However the preferred slip resistance test method for the HSE (Health & Safety Executive), the UKSRG (UK Slip Resistance Group) ,and TTA (The Tile Association) has been the Pendulum Machine.

BS5385 Part 3:2014 (Design and Installation of Internal and External Ceramic and Mosaic Floor Tiling in Normal Conditions) and BS5385 Part 4:2015 (Design and Installation of Ceramic and Mosaic Tiling in Specific Conditions) also refer to the Pendulum Test as the preferred test method.

Since 2003 the harmonised European standard – EN 14231 – specifies only the Pendulum for testing the slip resistance of natural stone flooring.

Pendulum Test Values (PTV) are placed into three categories:

  • PTV <25: High Slip Risk
  • PTV 25 to 35: Moderate Slip Risk
  • PTV 36+: Low Slip Risk

The PTV values and categories were created from thousands of pieces of data collated by the HSE for various slipping accidents over many decades, for example:

  • PTV18 – risk of 1 person in 2 slipping
  • PTV24 – risk of 1 person in 20 slipping
  • PTV29 – risk of 1 person in 10,000 slipping
  • PTV34 – risk of 1 person in 100,000 slipping
  • PTV36 – risk of 1 person in 1 million slipping

It must be noted that, in general, all ceramic and stone floor tiles are PTV36+ when in a clean and dry state.  It is the effect of a contaminant that changes the PTV value of a flooring installation, the most common contaminants being water, or general dust/dirt.  PTV Values are, therefore, commonly noted as PTV Wet, for example PTV36+ (Wet).

Correct specification and cleaning/maintenance programmes should be in place for all flooring materials. For example, a textured flooring may offer higher initial PTV values when installed, but it may be difficult to maintain in its original state, because it is difficult to clean.

The floor’s PTV value (coefficient of friction) will, therefore, reduce quickly, leaving a floor with a lower (much lower in most instances) PTV value than a “smoother” correctly specified product which is easier to maintain. Correct and relevant specification of an area’s slip resistance needs is therefore extremely important.

For areas that do not have a foreseeable risk of contamination and have a suitable cleaning and maintenance regime the floor will effectively be in a clean and dry state.

DIN51130 R ratings – for shod traffic floors
For many years some specifiers have been using the R values as a rating system to a product’s slip resistance. R ratings range from R9 to R13. Because the ratings start at R9 there is a misunderstanding that R9 is slip resistant because there must be an R8, R7 and so on. This is a misconception - R9 is the lowest value for DIN51130.

R values fit into very broad categories, with the lubricant for the test being oil.  This means that this test method is not representative of general in-service shod traffic conditions.  The test procedure is also a laboratory test, meaning that it is not possible to carry out tests on installed products.

Recent analysis of published data for over 350 products (ceramics, stone, resilient flooring, laminates, etc) was undertaken to see if there is a correlation between R ratings and PTV.  The results will be very surprising to most specifiers:

9% of products rated as R9 had a PTV of 36+ (Wet) with 72% of products in the High Slip Risk Category PTV <25 (Wet).

32% of products rated as R10 had a PTV of 36+ (Wet) with 35% of products in the High Slip Risk Category PTV <25 (Wet).

78% of products rated as R11 had a PTV of 36+ (Wet) with 5% of products in the High Slip Risk Category PTV <25 (Wet).

From this analysis we can see that the R rating (whether R9, R10, or R11) does not give an accurate guide to the slip resistance of a material.

The biggest problem area is the assumption that R10 is a slip resistant product when only 32% of R10 rated products achieve PTV36+ (Wet).

It is important that to specify a reliable and predictable slip resistance value supported by HSE, TTA, UKSRG, and BSI, so the Pendulum Test Results should be used.

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