What does dishing or cupping mean?

Dishing or cupping in rubber tiles describes a bowl-shaped deformation in which the centre of the tile sits lower than its edges and corners. The edges do not have to rise for this shape to occur; it can result simply from the centre settling more than the rest of the tile.

Such settling is typically associated with the direct installation of tiles made from rubber granules on a layer of sand, chippings or gravel. During use, these materials can compact or shift sideways, leaving the rubber tiles without a flat bearing surface and causing them to follow the lowered substrate.

A defect in the tile’s design or manufacture can also cause cupping, as can a less densely compacted area in the centre of the tile.

Accordingly, rubber granule tiles should not be installed directly on sand, chippings or gravel. In a permeable construction, plastic honeycomb grids filled with chippings limit sideways movement of the chippings. These grids are also known as gravel grids and reduce uneven settlement.