A very common question we are asked is: Are porcelain pavers slippery when wet? And can they be used safely around swimming pools?
The rather simplistic answer typically given is that no, porcelain pavers are not slippery when wet. But the more realistic answer is that it depends on a large number of factors. Also, looking at the strict definition of slip resistance, and the official tests that are used to define this concept, what a homeowner might regard as ‘slippery’, does not always mesh with the rather clinical definition of slip resistance.
How is slip resistance tested?
All porcelain and ceramic tile manufacturers subject their products to a series of tests which enables them to quote figures for slip resistance. For example, there is a pendulum test which mimics the way a heel makes contact with a floor. And there are ramp tests (including DIN 51130, DIN 51097 (barefoot), BS 4592) where the data from each one is presented somewhat differently. As everyone knows, the sole on every shoe is different, with some materials being very good in dry weather, but rather poor in wet weather on a smooth surface. All standard tests are done under very strict standard conditions which cannot hope to replicate the full range of conditions the homeowner is likely to face when stepping out onto a wet porcelain paver. Which is why American National Standards Institute (ANSI) published some standards that attempt to classify, depending on the value of the dynamic coefficient of friction, there is a “lower probability of slipping” potential, an “increased probability …” and a “higher probability” of slipping on a specific surface.
What is the Dynamic Coefficient of Friction (DCOF)?
Without wishing to get too technical in this discussion, USA porcelain paver manufactures normally subject their pavers to testing for slip resistance under ANSI A326.3 American National Standard Test Method for Measuring Dynamic Coefficient of Friction (DCOF) of Hard Surface Flooring Materials. This test requires pavers to achieve a rating of >0.40 on DM236/89 B.C.R.A. DCOF. It is useful to note that even in this document it mentions there are many factors that affect the possibility of a slip occurring on a surface, including the material of the sole of the shoe, it’s degree of wear, the type and presence of surface contaminants on the paver, the speed and length of stride a person is taking at the time of the slip, whether the paved surface is flat or inclined and how effective the drainage is on the surface of the paver, amongst other factors.
The ANSI test is only based on using an SBR rubber test ‘foot’ and does not claim to have any correlation between actual footwear or how a movement is made on the surface by a person. It essentially involves dragging the rubber foot along a surface which has been wetted with water for a specified distance measuring the resistance.
Why do porcelain pavers often not drain as completely as concrete pavers?
Because porcelain pavers are essentially impervious to ingress of water, the surface is subject to a meniscus effect, just like glass where water tends to hang as a bead along the outside edges of a paver, which restricts surface water from completely draining. Under such circumstances, there can quite easily be a thin layer of water lying on the top of a porcelain paver until it evaporates or the edge meniscus is broken.
How important is surface texture on slip resistance of a porcelain paver?
Porcelain pavers are not manufactured with a smooth gloss finish like interior ceramic or porcelain patio tiles, but are normally produced with a textured surface which is molded or pressed into the surface of the paver before firing. The relative roughness or smoothness of this textured surface really just depends on the particular style of paver that the manufacturer is attempting to create and can vary quite widely across a manufacturer’s product range.
The problem for consumers is that looking at the paver manufacturer’s specifications is generally not likely to give you much indication of the relative slip resistance between one paver and another. Most manufacturers generally just state that a specific paver passes the particular slip resistance test, and don’t quote any absolute figure.
What are the pros and cons of using porcelain pavers in external wet areas?
There are of course advantages and disadvantages of using porcelain pavers in any application, but because they are much thicker than conventional interior tiles, porcelain pavers are specifically intended for outdoor use. Their extra thickness ensures that they do not crack or break easily, and they can even be used for elevated rooftop decks, supported only at each corner by adjustable height pedestals. So for most applications, they are perfectly good for outdoors use. That’s not to say there are no issues to be considered with using porcelain paving in every possible exterior application, since with any product, the design parameters and technical specifications of the product always need to be considered in relation to the intended use.
Are there products which can be applied to porcelain pavers to avoid them being at all slippery?
If you’re worried about possibly sliding or aquaplaning on a porcelain paver after a shower of rain and maybe injuring yourself, there are products that can be applied to the surface of pavers which increase traction and slip resistance. The most commonly used products are mildly acidic anti-slip solutions such as CoverTec’s ‘GripTreat’ that slightly etches the surface, allowing for an increased suction effect between the paver and the bottom of shoes. This treatment can be effective for increasing the slip resistance coefficient of dry and wet porcelain pavers, but as may be expected, is ineffective when the pavers are covered with snow or ice. Under such conditions, porcelain pavers can indeed be slippery underfoot, irrespective on any surface treatment.
Which is best around a pool, porcelain pavers or travertine?
if you’re planning to use porcelain pavers around a swimming pool, it’s best to use pavers which have a more textured surface. If you’re considering limestone, sandstone or travertine pavers, natural travertine is certainly more water absorbent than porcelain pavers, but the downside is that it will stain more easily and be more subject to moss and mold. But the upside is that it will probably be more slip resistant. If those disadvantages of travertine are a concern, be aware that travertine look porcelain pavers are also available in styles and colors that very realistically replicate the look of natural travertine, but are totally stain resistant and also resistant to build up of moss and mold.