What does dishing or cupping mean?

Formation level conditions can be associated with a dish-shaped deformation in rubber granule tiles, in which the centre of a tile sits lower than its edges and corners. The edges do not need to lift; the shape may arise solely because the centre has dropped further.

This deformation commonly occurs where tiles made from rubber granules are installed directly on a bed of sand, chippings or gravel. During use, these materials may compact or move sideways, so that the rubber tiles no longer sit flat and follow the lowered substrate.

A defective tile design or manufacture can also cause this form of deformation, as can a central area that has been compacted less than the surrounding area.

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 filling. These grids are also called gravel grids and reduce uneven settlement.