“Slip resistance is a fixed value, if I lay a 43PTV tile, or improve an existing floor to 43PTV, it will still be 43PTV in a year...”
This was the line of thought held by a Client I visited this week, and it is by no means uncommon. If slip resistance really were a constant I would be out of a job. Luckily for me, and sadly for those responsible, flooring products will inevitably change over time. If you consider a car tyre as an analogy, it may be rated for very good grip from the factory, however it will perform differently depending on whether it is installed properly, whether it is wet or dry, whether it is clean or dirty, the type of road (shoe sole) surface and how worn the profile is. It is only necessary for the tyre/floor to provide less than adequate grip in one condition/situation and an accident or near miss will occur.
Dry values may actually increase over time, as the surface is worn smooth (think slick tyre), however it is still important to clean the surface to prevent marbling underfoot. Almost all surfaces present comfortably safe grip levels in clean and dry conditions, for the lifetime of the product. If you can maintain a surface in a clean and dry condition reliably in end use, you probably don’t need to worry about slip accidents.
Slip accidents generally happen in the wet and the wet slip resistance of flooring surfaces typically decline over time, reaching an equilibrium point when cleaning removes as much dirt as has accumulated between cleans, until wear eventually destroys the profile. It is important to note that declines occur in the short, medium and longer term.
In the short term between cleans, the surface will accumulate dirt which smoothes the profile, reducing wet slip resistance. Regular cleaning will reduce the extent of this decline, ensuring the surface remains safe in the wet.
In the medium term the effectiveness of cleaning at removing all of the ingrained dirt comes in to play. In a commercial environment ‘perfect’ cleaning is unusual if not impractical. A small amount of dirt will typically remain in the surface after cleaning. The effectiveness of cleaning will determine how much dirt is left behind after each clean, and how quickly the dirt will have clogged enough of the floor profile to make it slippery when wet. This may occur in days, weeks or months, dependent on traffic levels, contamination types and cleaning regime. A safe surface can be maintained in the long term by ensuring the surface is rough enough to allow ‘imperfect’ commercial cleaning, with residual dirt left in the profile, and accumulated dirt from a period between cleaning, whilst still presenting sufficient profile depth to disperse a fluid film and offer safe wet grip.
In the long term the abrasive action of pedestrians crossing the surface will wear down the floor profile, in much the same way as a tyre profile is worn with use. This will again smooth the surface, impacting wet slip resistance performance. This mechanic will depend on the floor surface and traffic type/volume, but will typically occur over a period of years or tens of years.
At this point you’d be forgiven for thinking that if initial PTV’s are temporary, surely they are meaningless. Despite the movable nature of slip resistance, it is actually straightforward to provide a safe surface in the long term. First, you must ensure the flooring product offers safe grip levels. This can be achieved through manufacturer data, or an in situ test. You are looking for 36PTV or greater in the conditions of end use (wet or dry, shod or barefoot). Ideally, look for a small margin above 36PTV, to permit a small decline from the mechanics outlined above. In situ tests are useful because they reflect the real condition of the floor, with existing cleaning and re-contamination rates. If the flooring is not compliant, improve it (we can impartially advise how). If the flooring is compliant, certify it (our certificates are regularly used in court). Depending on environment and results achieved, the floor should be tested again, typically in 3, 6 or 12 months time. This is crucial in maintaining both a safe surface and a continuous record of compliance for the surface. If the surface is not compliant, improve it, armed with the knowledge that a compliant value can be achieved and that cleaning regimes are likely a quick and easy fix. If the surface is compliant you now have a period covered by two independent test certificates showing the surface achieved a safe (if not consistent) level of grip. Any slip accident claims arising for the period between tests (typically you may not know about them until 3 years after the ‘alleged’ slip), can be defended effectively, saving time money and expense.
It is worth noting that some flooring manufacturers and anti-slip contractors offer a “guaranteed slip resistance for the life of the product”. Whilst it is certainly the case that there are some great anti-slip products out there, I would be very wary of slip performance guarantees, unless they are supported by regular (expert and independent) monitoring. Unscrupulous suppliers have been seen to dupe customers with misleading marketing, and whilst reputable suppliers may be able to accurately predict results with wear tests, the unpredictable process of cleaning/contamination also plays a significant role. Where cleaning regimes are (sensibly) specified by suppliers any variation may result in both a slippery surface and a voided guarantee. As mentioned above, ‘perfect’ cleaning is unusual if not impractical in a commercial setting.
In short, if you aren't monitoring the slip resistance of you floor regularly, you can't know if it is safe.