Can I lay rubber tiles on stone chippings or gravel?

For most rubber tiles to stay level on stone chippings or gravel in the long term, the loose material must first be stabilised with plastic honeycomb grids. These are sold under various names, including gravel grids, grass grids and honeycomb gravel grids. In each case, the cells hold the chippings in place and stop them shifting.

Chippings are generally of a similar size, with no fine material to fill the gaps between them. They cannot therefore be compacted effectively and remain prone to movement. Walk across chippings or gravel and you can feel them shift underfoot and hear them crunch. Beneath a rigid concrete slab, that movement hardly matters. Beneath a rubber tile 2 to 5 cm thick, however, hollows develop in the bed and show through on the tile surface.

First, remove the topsoil and level the ground to the required formation level. Spread a thin layer of chippings over the prepared ground and screed it carefully to a flat finish. Lay the gravel grids on top and fill the cells flush with their upper edges. Use crushed chippings rather than rounded gravel, as their angular particles interlock much better. Then lay the rubber tiles on this bed. Where the ground has poor load-bearing capacity, or where the build-up needs to withstand frost, install and compact a sub-base beneath the laying course of chippings.

Certain WARCO ranges with a flat underside are approved for installation directly on a bed of chippings, without a gravel grid. These ranges always require a sub-base of compacted crushed stone (MOT Type 1). Over this, spread a 2 to 3 cm laying course of crushed sand and chippings graded 0/5, then screed it level and compact it with a plate compactor. Unlike chippings alone, this mix contains fine sand, which allows it to firm up.

The laying course must remain within that thickness range. Below 2 cm, it cannot be screeded and compacted properly; above 3 cm, too much loose material remains beneath the patio tiles. After compaction, check the surface with a three-metre straightedge: the gap beneath it should be no more than 0.5 cm anywhere.