How water-permeable are rubber tiles?
Rubber tiles made from polyurethane-bound rubber granules have an open-pored structure. Water travels through the interconnected voids between the bonded granules, not through the rubber itself. How much water a tile lets through depends on how densely the granules are pressed together. The key factors are particle size distribution and moulding pressure.
At low moulding pressure, irregularly shaped granules lie loosely together, so interconnected pores and fine channels remain open. Water then flows vertically down through the tile. In testing to BS EN 12616, an accredited institute measured more than 1,100 litres per square metre per hour, even after four weeks of weathering. At high moulding pressure, the granules lie with almost no gaps between them, so very little water gets through. The figure for each product is given in its description as a comparative value.
A freshly laid surface may allow water through more slowly during the first few days than its test figure would suggest. At first, the granule surfaces do not wet readily, much like the surface of a new raincoat. After several days of use, the rubber flooring reaches its full water permeability. Scrubbing the surface with a little washing-up liquid can speed up this process.
The test report may be submitted to the building control authority as evidence of water permeability. Classification of the finished area depends on the complete build-up. Rainwater can infiltrate through the rubber flooring into the ground only if the sub-base beneath it is permeable as well.