Non-slip flooring is an important safety issue, but it’s plagued by confusing standards and complicating factors. Barbour Index and Scott Brownrigg can put you on a firmer footing
Statistics show many thousands of people have accidents by slipping on floors. What’s more, some aspects of slip resistance and wear can frequently cause problems within a short time of a building’s completion. Therefore the ability of any flooring to provide a reasonable level of grip is fundamental. This is particularly important for commercial buildings, especially in the entrance area. However it is not always easy to specify non-slip flooring as the trade bombards specifiers with misleading and often completely inaccurate literature, and there are several methods of assessing the slip resistance of flooring.
1.What makes flooring non-slip?
It is important to understand several principles. The ability of a surface to provide grip is provided by its surface roughness on a microscopic level. The second fundamental is the coefficient of friction. Finishes that are polished, inherently smooth or hard and lacking texture will not resist the shear forces of a shoe moving obliquely over the surface, causing it to slip.
Additionally, if the surface is soiled with anything such as water – or, worst of all, oil – any slip resistance that the floor did have will be lost.
Any changes in the surface can also result in a problem – for example the metal frame to an inset manhole or a separator strip. This is enough to unbalance a person and cause an accident.
Several competing methods of testing are used by the industry. The most consistent, and the one recommended by the Health and Safety Executive, is the pendulum. This measures the ability of a flooring material to slow down a standard pendulum as it is swung across the surface at a standard rate. A scale measures the amount of up swing remaining after contact between the two surfaces. A higher level of up swing will result in a smaller slip resistance value. Pendulum values of 25 and below should be regarded as poor, 26-36 medium and above 40 good. Samples are tested dry.
Additionally the surface roughness of the material should be established in microns. It can be measured using a surface roughness meter which will drag a probe over the surface of the material and measure the peak to trough value. This will establish the ability of the material to maintain some resistance even when contaminated.
A surface roughness (Rz) of 10 or below is poor, 10-20 is medium, 20-30 is good, and above 30 is extremely good.
The published literature across the industry quotes all types of tests and standards that in some cases may be highly misleading. The often-quoted DIN 51097:1992 and DIN 51130:1992 tests result in a scale of values starting at R9 for the lowest and R13 for the highest. These relate to a test used widely in Europe called the ramp test. It relies on establishing the point where a person will slip using standard soled shoes or bare feet on a ramp that steadily increases in elevation. It is not as consistent as the pendulum test.
3. Slip resistance vs cleanliness
Cleanliness is important, particularly in healthcare facilities. However there is a perception that a clean floor is a shiny floor, which is not necessarily the case. In fact most of the time a shiny floor is dangerously slippery, especially if wet. Flooring companies are working on cleaning techniques that clean but leave the surface matt.
It is possible that the floor could be contaminated by spilled liquids, resulting significant loss of resistance. Surface roughness can be tabulated against the potential contaminate with a view to maintaining some slip resistance even after a spillage. Typically any water will require a surface roughness of at least 20 microns, soap 45 microns and oil at least 70 microns.
It is tempting to specify a vast area of smooth flooring in entrance areas to create a good impression. However when these get wet from moisture dragged in from the outside they become slippery, and invariably have to be covered in additional matting.
This of course detracts from the intended appearance and a better solution is to specify an appropriate material throughout from the beginning.
5. The Disability Discrimination Act
It is also important to realise that a shiny surface produced during polishing could be confusing to the visually impaired and therefore in conflict with BS 8300 and possibly the Disability Discrimination Act. Both these standards call for visual contrast so the specifier needs to consider the colour, the context and surface reflectance together. It is also part of the specifier’s responsibility under CDM to ensure that the method of cleaning and maintenance to ensure continued performance is included in the health and safety file.
Designers and specifiers should consider from the outset the volume of traffic across the floor and the likely degree of soiling. This is particularly important in entrances and areas such as kitchens. Consideration must be given to the ability of the finish to resist wear and to be cleaned easily and adequately. Look carefully at the manufacturer’s information and insist on looking at a similar installation that has had at least five years’ use. Also review the recommended cleaning regime and consider the implications for the user. It is also important to understand if the floor will be subject to traffic other than footfalls.
BS 7967, parts 1-3, 2002: Pendulum Testers The Measurement of Floor Slip Resistance: Guidelines recommended by the UK Slip Resistance Group 2000.
DIN 51097:1992 Testing of Floor Coverings; Determination of Anti-Slip Properties; Walking Method
DIN 5110:1992 Testing of Floor Coverings; Determination of Anti-Slip Properties; Work Rooms and Work Areas. The Workplace 1992 HMSO