How water-permeable are rubber tiles?

Rubber tiles can be water-permeable at rates ranging from nearly zero to more than 1,100 litres per square metre per hour. Water permeability depends on the particle-size fraction of the rubber granules used and on the pressing pressure applied during manufacture. The tiles are made from PU-bound rubber granules and have an open-pored structure.

Within this porous structure, water does not pass through the rubber itself but through the voids between the bonded granules. The more tightly the granules are compacted, the less water a rubber tile allows through. At low pressing pressure, the irregularly shaped granules sit loosely beside one another, leaving interconnected pores and fine channels through which water flows vertically downwards. An accredited institute measured more than 1,100 litres per square metre per hour in accordance with BS EN 12616, even after four weeks of weathering.

The respective water permeability value is stated as a comparative value in the product description. Rubber tiles made under high pressing pressure have an almost void-free granule structure and allow hardly any water through. A newly laid area absorbs water more slowly during its first days than the measured value may suggest, because the granule surfaces initially resist wetting, much like a new rain jacket. After several days of use, the floor covering reaches its full water permeability; scrubbing it with a little washing-up liquid speeds up this process.

The test report can be submitted to building authorities as evidence of water permeability. How an area is classified depends on the overall system build-up: precipitation can drain through the floor covering into the ground only if the sub-base beneath the rubber tiles also absorbs water.