How do I lay rubber tiles over natural stone paving?

Rubber tiles can be laid directly over natural stone paving where the substrate is firm, level and load-bearing. Outdoors, the substrate must have sufficient gradient leading to a free edge or drainage outlet. Sawn or ground natural stone slabs are generally suitable, including granite, marble, sandstone, travertine and slate. The tiles are not bonded to the natural stone; depending on the range, they are joined with interlocking puzzle joints or plastic connectors. Water passing through the tile covering or its joints must be able to drain freely over the natural stone slabs.

Natural stone paving made from stone setts, split-faced slabs or polygonally laid slabs is often too uneven. Domed or unevenly raised stones, wide joints, and sunken, tilted or loose elements prevent full bearing contact. Loose or sunken stones must be reset to the correct level, while wide or washed-out joints require permanent filling and remaining irregularities must be levelled. Where settlement or deformation affects a larger area, levelling the bedding alone is insufficient.

After the natural stone covering has been removed, the exposed bedding, underlying sub-base and formation level must be checked for load-bearing capacity and drainage, then repaired where required. An even levelling layer is formed over a load-bearing base compacted to the required profile, followed by fillable plastic honeycomb grids, which are also sold as gravel or grass grids. Their cells are completely filled with washed, angular, frost-resistant chippings and levelled flush with the surface. The grids prevent lateral movement of the chippings and provide a dimensionally stable, level bearing surface for the rubber tiles. Drainage must be maintained throughout the entire base construction.

Where the natural stone was laid in a mortar bed over concrete, any loose or protruding mortar residues must be removed. The exposed concrete must be load-bearing, level and adequately drained.