How are gravel stabilisation grids installed to form a sub-base?

Gravel stabilisation grids can be installed as a sub-base in three ways: directly on in-situ ground, on a grit laying course over the formation, or on a crushed-stone sub-base.

The grid cells are filled with crushed, angular grit. The cells are filled to the top, and the grit is levelled flush with their upper edges.

Where the ground has sufficient bearing capacity and is only lightly loaded, installation directly on in-situ ground is sufficient. Topsoil must first be removed, and the formation must be carefully prepared. The grids are laid directly on the natural ground, allowing the 4 cm ground spikes to penetrate the soil.

A thin grit layer can be laid over the formation to even out irregularities. The ground spikes extend through this grit layer and into the formation.

Where the ground has a low bearing capacity, protection from frost effects is required, or high loads are expected, a crushed-stone sub-base must first be installed and compacted. The ground spikes cannot penetrate the compacted crushed stone. A grit layer is therefore laid over the sub-base so that the spikes are fully embedded. This grit layer must be at least 6 cm thick, and the grids must sit firmly on it.

Gravel grids are also sold as grass grids or plastic cellular grids. The grids are set into the thin grit layer, which is about 2 to 5 cm thick when used to even out irregularities.