How should safety tiles be laid on sand, gravel or chippings?

Impact-absorbing safety tiles must not be laid directly on sand, gravel or chippings.

Loose aggregate beneath the elastic tiles does not provide sufficient positional stability. Plastic honeycomb grids address this issue. They are also known as gravel grids, grass grids or ground grids. The grids divide the area into numerous small cells, which retain the infill laterally and protect it against displacement and washout. This creates a permanently stable, level and water-permeable sub-base for the impact-absorbing safety tiles.

Without the cells, sand, gravel and chippings remain mobile under load. Over time, the heavily profiled underside of the impact-absorbing safety tiles can press into the loose aggregate. Material may move from the centre of the tile towards its edges, creating hollows in the bedding. The elastic impact-absorbing safety tile follows these hollows, sinking in the middle and potentially lifting at the edges. This pattern of damage is known as dishing or cupping.

When preparing the substrate, a level formation level with adequate load-bearing capacity must be formed. Layers that are not load-bearing or are easily deformed must be excavated to the extent required by local ground conditions and the intended load. This applies particularly to loose play sand. Where the substrate has limited bearing capacity, is cohesive or is susceptible to frost, the excavation is filled in layers with suitable crushed stone and carefully compacted. On firm ground with low to medium loading, an additional crushed-stone sub-base may not be necessary, depending on the installation conditions.

Depending on the substrate, the plastic honeycomb grids are laid either directly on the prepared formation level or on a thin, levelled layer of chippings. The thickness of the chippings layer depends on the selected construction and local conditions. The earth spikes on the underside of the grids are about four centimetres long. They engage with the underlying layer and assist in anchoring the grids. A general minimum chippings-layer thickness of 6 cm is not required.

The cells are then filled to their upper edge with suitable chippings or gravel. Crushed, angular aggregate is advantageous because it interlocks well. The infill is carefully brushed in, topped up where necessary and levelled flush with the upper edge of the grids. The impact-absorbing safety tiles then rest across the filled honeycomb structure rather than only on the grid ribs. This provides a stable, water-permeable sub-base formed by plastic honeycomb grids.

The impact-absorbing safety tiles are laid and connected in accordance with the relevant installation instructions. Whether edge restraint is required depends on the product range, the connection system and the installation conditions. Some product ranges are expressly approved for installation on a thin layer of chippings.