Can gravel be compacted before laying rubber patio tiles?

Gravel can be compacted with a plate compactor to form a laying course beneath patio tiles. The rubber patio tiles are then laid loose without mortar or adhesive (dry-laid) on top. For the laying course to compact, the aggregate must contain fines, as in 0/5 grit sand: the fine sand fills the gaps between larger particles and firms up the layer. Single-sized chippings without fines, such as 2/5 or 2/8, remain loose even after compaction and do not provide a stable laying course for elastic patio tiles made from PU-bound rubber granules. The laying course directly beneath the rubber tiles must also be level to a tight tolerance.

Over a sub-base of compacted crushed stone (MOT Type 1), the 0/5 grit sand is screeded to a thickness of 2 to 3 cm, then compacted with a plate compactor until the gap beneath a 3 m straightedge is no more than 0.5 cm at any point. This method may be used only with product ranges that have a flat underside: an elastic rubber tile settles into hollows in the bed, whereas a rigid slab would span them.

The recommended build-up uses gravel grids: plastic honeycomb grids that hold the chippings in their cells. The grids are laid over the compacted formation, with a thin layer of chippings beneath them used only to level out variations in height. The cells are filled with crushed stone chippings flush with their top edges, as angular crushed stone interlocks better than rounded gravel. Held in the cells, the chippings cannot shift, so the bed stays level and the rubber tiles sit flat.