Suggested Specifications for Lifetime Slip Resistance of Flooring

When we’re buying new automobile tires we’d like to know not only that the tires are good at the time of purchase, but that they will have a reasonably long lifetime for us. Michelin, for instance, offers models with mileage warranties (within a time limit) from 36,000 to 80,000 miles.

When buying slip-resistant flooring, customers are usually forced to make a decision based on the reported slip resistance at the time of manufacture — not at the end of an economically reasonable lifetime. They might be hoping that the flooring will give safe service for a number of years, but find that it becomes slippery after only a matter of weeks in use.

The purpose in buying safe flooring should be not just to pass an initial inspection, but also to provide safe long-term usage.

There’s now a suggested way of specifying minimum flooring wet slip resistance after a standard wear test in order to come up with a reasonable requirement that will help ensure a reasonable economic lifetime for new flooring. We’ll tell you about that here.

Slip Resistance test results from the McDonald’s Restaurants Sustainable Slip Resistance Test are believed to indicate reasonably the slip resistance of a flooring sample after one or two years in the customer area of a busy McDonald’s Restaurant. This has helped McDonald’s and our clients to avoid expensive mistakes when specifying and purchasing flooring. In some cases flooring has good slip resistance when it’s delivered, but that slip resistance disappears after several weeks or months of use. The customer is stuck with a hazard to remediate somehow. The vendor will have moved on. McDonald’s requires a minimum wet Pendulum Test Value of 35 after 500 cycles of a standard specified abrasion technique. Some environments (outdoor stairs, etc.) might need more stringent requirements.

Recommended new-flooring slip resistance safety standards for many types of situations (commercial kitchen, pedestrian crossing, bathrooms in hospitals and aged care facilities, swimming pool decks, etc.) are shown elsewhere in this blog. These are based on pendulum DCOF tests applicable to the time of purchase. In establishing the minimum wet Pendulum Test Values (PTV_, Standards Australia allowed for some deterioration of the slip resistance over time. However, they gave no indication as to what the expected (or allowable) deterioration might be.

A recent thesis by Adoración Muñoz Lázaro at Universitat Jaume I [King James I], Castellón, Spain, looks in some detail at the slip resistance loss of many types of tiles in comparison with the number of persons actually visiting the areas, ranging up to 120,000 people. In many cases there was significant slip resistance loss after 50,000 pedestrian uses. This will of course vary with type and amount of mineral soil, type of flooring, hours of rainfall, and other variables. Many thriving businesses (like a busy McDonald’s) have over 1,000,000 visitors/customers a year, so that 50,000 people pass through in only 18 days! This is not an economically reasonable lifetime for ceramic tile, marble, limestone, etc. It seems obvious that ex-factory slip resistance data alone are of little use to the customer.

Richard Bowman of Intertile Research, Australia reviewed Muñoz’ work in May 2020: “A view of slip resistance and Accelerated Wear Conditioning (AWC) post Muñoz”.

Using the assumption that AWC procedures might cause wear that might not occur in the real world, Bowman posits that the results could represent the “worst case scenario.” If so, perhaps the wet PTV result at 500 cycles of wear in the McDonalds test represents a reasonable indication of long-term wear. He calls such values the maintenance value. They could be used (1) as a minimum value for specifications, and (2) as a critical checkpoint for on-site audits.

Table 1 shows Bowman’s proposal for specification. The “Class” column denotes the slip-resistance levels shown in our table of Australian standards, and the next column shows the corresponding “Minimum Slip Resistance Value” (SRV, or PTV) in our table. Bowman’s Maintenance Values are, for instance, a minimum mean PTV of 27 for an initial recommended PTV of 35. The “Individual” maintenance values (e.g. 22 for an initial recommended PTV of 35) are defined by the Australian standards and may involve wear-testing five or 10 or more new specimens from a lot.

after-wear slip resistance test criteria

Table 1. Bowman tentative suggestions for after-wear test criteria

Improper maintenance can rob a floor of its wet slip resistance much faster than foot traffic. Use of an abrasive rotary pad in an autoscrubber or floor machine is one culprit. If a rotary machine is used it should have a very soft brush, like a carpet brush. It’s necessary to police maintenance procedures to make sure they are followed consistently — otherwise they won’t be.

Cleaning a hard floor with a mop is similar to cleaning a carpet with a broom: it doesn’t effectively remove soil and may leave a hard floor slippery. Too often the mop and water are dirty too, and the soil is not efficiently removed though it might be distributed more evenly. More effective is use of an autoscrubber, which provides agitation (with a soft brush) with vacuum from an opposed pair of squeegees to remove the dirty water.

In the case of resilient flooring, where the properties might remain constant as the material wears away, or the actual walking surface is a floor finish (“wax”) that is periodically renewed, the ex-factory slip resistance might be more relevant and Accelerated Wear Conditioning might not be needed.

To specify safe tile, stone, etc. use the recommended minimum initial PTV from our standards table, which considers numerous conditions of use. Then refer to the “Minimum mean” in Table 1 above to get reasonable requirements for wet slip resistance projected into the future. Safety Direct America is here to conduct those tests for you. Our qualifications for testing are discussed elsewhere in this blog.

Our exclusive SparkleTuff™ transparent anti-slip coating has a wet PTV that only decreased from 63 to 61 in the McDonald’s Sustainable Slip Resistance test. That is in the highest category in Table 1, which has a highest “Minimum Mean” of 40, and it indicates a potentially long useful safe lifetime for SparkleTuff™ in use — many years in typical situations. When dry, SparkleTuff™ has the same slip resistance as an NBA basketball floor.

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