How do I lay patio tiles on a bitumen membrane or roofing felt?

Patio tiles made from PU-bound rubber granules are laid as a floating installation on a bitumen membrane, roofing felt or flat-roof membranes: they are simply placed in position, without adhesive or screws. This keeps the waterproofing on a balcony, terrace, roof terrace, flat roof or carport intact and allows individual tiles to be lifted at any time. Damaged waterproofing must be repaired before installation.

For plastic flat-roof membranes, it must be established before installation whether they contain plasticiser; the membrane manufacturer or a roofing contractor can provide this information. Roofing felt and bitumen membranes contain no plasticiser, so the tiles may rest directly on them; EPDM flat-roof membranes are also plasticiser-free. PVC or FPO plastic membranes can contain plasticiser, which may migrate into the rubber tiles on direct contact and cause the membrane to become brittle over time. Where a plastic membrane contains plasticiser, a thin separation layer of polyester or glass fibres is placed between the membrane and the rubber-granule covering. Plasticiser migration does not harm the rubber tiles.

The water-permeable rubber-granule covering allows rainwater to pass through the tiles onto the waterproofing, where it follows the existing fall to the outlet. On most ranges, drainage channels on the underside of the tiles carry the water onwards. A fall of 1 to 2 % has proved effective. Before installation, check the waterproofing for irregularities or depressions where water may collect, and level these areas with accurately cut pieces of roofing felt during installation.