Gravel Grid Calculator

Gravel grids (also called ground grids, cellular paving, or geocells) are interlocking plastic panels with a honeycomb or cell structure. You lay them on a prepared sub-base and fill the cells with gravel. The grid walls hold the gravel in place, preventing it from spreading, rutting, or migrating under foot or vehicle traffic. This creates a firm, stable surface while maintaining the natural look and drainage benefits of loose gravel.

The most common UK gravel grid panel is 500mm × 500mm (0.25m²), typically 30mm or 40mm deep. Panels interlock on all four sides and can be cut with a saw to fit irregular shapes. Some manufacturers offer larger 1m × 1m panels, but the 500mm format is dominant in the UK market because it's easier to handle and wastes less material when cutting to shape.

Gravel grids typically reduce the amount of gravel needed by around 15–20% compared to laying gravel without grids. The cells hold the gravel at a consistent depth and prevent it spreading outwards, which means you don't need to over-fill to compensate for migration. Our calculator uses an 85% fill factor — meaning you need 85% of the gravel you'd use for the same area without grids.

Yes — most gravel grids are rated for vehicle traffic. Standard 30mm grids handle regular car traffic on residential driveways. Heavy-duty 40mm or 50mm grids are available for commercial applications or areas with frequent heavy vehicle access. Always check the manufacturer's load rating, but a typical 30mm residential grid supports loads of 250+ tonnes per square metre when properly installed on a compacted sub-base.

Yes — gravel grids are not a substitute for a proper sub-base. You need a compacted layer of MOT Type 1 underneath (typically 100mm for foot traffic, 150mm for cars). The grid sits on top of the sub-base and contains the surface gravel layer. Without a sub-base, the grid will sink and deform under load, especially on soft ground.

Angular gravel in the 10–20mm range works best because the sharp edges interlock within the cells. Golden gravel, grey granite, and limestone chippings are popular choices. Avoid very round stones like pea gravel, which tend to sit above the grid cells rather than bedding into them. The gravel size should be smaller than the grid cell depth — don't use 40mm stone in a 30mm grid.

Prepare the sub-base (excavate, lay membrane, add and compact MOT Type 1). Lay the grid panels on the compacted sub-base, interlocking them as you go and cutting edge pieces to fit with a handsaw. Fill the cells with gravel, slightly overfilling by 5–10mm to allow for initial settlement. Compact lightly with a plate compactor or tamp flat by hand. Top up any low spots after a week of use.

For driveways and parking areas, absolutely. Grids typically cost £3–£6 per m² and prevent the most common gravel driveway problems: rutting, spreading, and migration. Over 5–10 years, you'll save money by not needing to top up displaced gravel. Grids also make gravel surfaces wheelchair and pushchair accessible, which is increasingly important for front garden parking areas. For purely decorative areas with no traffic, grids are less critical.