How water-permeable are rubber tiles?
Rubber tiles can be water-permeable at rates ranging from almost zero to over 1,100 litres per square metre per hour. Water permeability depends on the particle size of the rubber granules used and on the pressure applied during manufacture.
The tiles consist of rubber granules bound with PU and have a porous structure. Water does not pass through the rubber itself, but through the voids between the bonded granules: the more densely the granule structure is compacted, the less water can pass through it. At low pressure, the irregularly shaped granules lie loosely alongside 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, including after four weeks of weathering. Rubber tiles manufactured under high pressure have an almost gap-free granule structure and allow very little water to pass through. The relevant value is stated as a reference value in the product description.
A newly laid area allows water to pass through more slowly during its first few days than the test value may suggest because the granule surfaces are initially difficult to wet. After several days of use, the rubber tile covering reaches its full water permeability; scrubbing with a little washing-up liquid accelerates this process. The test report can be submitted to building authorities as evidence of water permeability. How an area is classified depends on the complete construction: rainfall can infiltrate through the covering into the ground only if the sub-base beneath the rubber tiles also absorbs water.