Are outdoor rubber tiles non-slip when wet or in the rain?
Floor coverings made from polyurethane-bound rubber granules are tested for slip resistance and achieve class R10 under BS EN 16165. During the test, an operator wearing standardised test footwear walks on an inclined plane with lubricant applied to its surface. Depending on the product range, the mean angle of acceptance is between 12 and 17 degrees. For dry conditions, class DS to BS EN 14041 is also declared. Slip-resistant is the technically accurate term, as no surface can provide grip in every condition.
Grip comes from the granular surface and its open pore structure. The shoe sole spans individual granules and deforms around them. This deformation accounts for most of the friction. As the floor covering itself also yields under load, the contact area between the sole and the surface increases.
In rain, water permeability is also relevant. Testing by an accredited laboratory to BS EN 12616 recorded more than 1,100 litres per square metre per hour. Rainwater therefore passes through the tiles instead of remaining on the surface, then drains away through channels on the underside. Provided the pores remain clear, a continuous film of water does not form between the sole and the surface.
Moisture alone is not the same as a layer covering the surface. Wet leaves, snow, ice and a thin film of algae after a mild winter can lie between the sole and the surface, so the texture of the tile can no longer provide grip. Keeping the area clear of leaves, sweeping it regularly and removing oil or grease promptly helps retain grip over the years.