Gravel Stabilisation Calculator

Q: How many gravel stabilisation grid panels do I need?

Divide your total area by the area of one panel. A typical gravel grid panel measures 600 x 400 mm (0.24 m2) or 500 x 500 mm (0.25 m2). For a 30 m2 driveway using 0.24 m2 panels: 30 / 0.24 = 125 panels. Add 5-10% for cutting at edges and around obstacles. Panels interlock and are usually sold in packs covering 4-10 m2 - check the pack coverage on the supplier's listing. The gravel infill typically requires 20-25 kg/m2 for a 50 mm grid depth.

Q: What gravel should I use to fill stabilisation grids?

Use angular or crushed stone aggregate (not smooth rounded pea gravel) for the best stability and load-bearing performance. The stone size should match the grid cell size - typically 10-20 mm aggregate for standard grids. Angular stone locks together and resists displacement better than smooth gravel. Popular choices include 10 mm or 20 mm crushed granite, limestone, or flint. Decorative coloured gravels can also be used. Avoid large stones (over 20 mm) that will sit proud of the grid surface and become a trip hazard.

Q: What sub-base do I need under a gravel grid?

For a pedestrian path or light-use area: 50-100 mm of compacted MOT Type 1 or Type 3 sub-base over a compacted subgrade, plus a geotextile membrane to prevent fines rising into the gravel. For a driveway with car traffic: 150 mm of compacted Type 1 sub-base. For heavy vehicles or frequent use: 200 mm Type 1. The sub-base must be thoroughly compacted before laying grids. A weed membrane over the sub-base (under the grids) prevents weed growth from below without blocking water drainage.

Q: Is a gravel grid driveway classed as a permeable surface?

Yes - a gravel stabilisation grid infilled with gravel is a permeable surface that allows rainwater to drain through to the sub-base and into the ground below. This means that under the Town and Country Planning (General Permitted Development) Order 2008, paving a front garden with a gravel grid system does not require planning permission, regardless of the area covered. This is a significant advantage over impermeable surfaces (solid concrete or tarmac) which require planning permission for front gardens over 5 m2. Gravel grids also qualify as a SuDS (Sustainable Drainage System) compliant surface.

Q: Can gravel grids be driven on by cars?

Most gravel stabilisation grid systems are rated for domestic vehicle loads (typically up to 3.5 tonnes per axle). Some heavy-duty grids are rated for HGV or commercial vehicle use. Always check the manufacturer's load rating before use. The key factors for driveway performance are the sub-base depth and compaction, the grid depth and cell wall height, and the gravel infill. A 50 mm deep grid on a 150 mm Type 1 sub-base is suitable for typical car use. A thinner grid or inadequate sub-base will allow the grids to flex and the gravel to migrate.

Q: How do I prevent gravel from spreading or migrating?

Gravel stabilisation grids are the most effective way to prevent gravel migration - the interlocking cells hold the aggregate in place under vehicle loads and foot traffic. At the perimeter, use a solid edging system (timber, metal, or concrete kerb) to contain the grids and prevent them from spreading outward. Rake the gravel back level periodically as it will gradually redistribute with use. Ensure the gravel is filled to the top of the grid to provide a stable, flush surface. Do not overfill - proud gravel that sits above the grid is unstable and will spread.

Gravel Stabilisation Calculator

Grid panels, gravel fill, membrane, edging, pegs, and sub-base - everything you need for a stable gravel surface.

Grid / cell type - select the panel you're using

Panel m²: -

Use custom panel size

Gravel infill material

Gravel fill depth (mm) Fill to grid depth or slightly proud (3-5 mm above). Typical grids: 30-50 mm depth.

Overage / Waste (%)

Include weed membrane Geotextile membrane under the grid. Add 10% for overlaps.

Include MOT Type 1 sub-base

Include perimeter edging Gravel edging restraint to contain the grid. Calculated from total perimeter.

Include ground anchor pegs Typically 1 peg per 0.5 m² - holds grid flat during fill.

Areas

Your areas

Area name Length (m) Width (m)

Job Costing (optional)

Grid panels per m²

Gravel per tonne

Membrane per m²

MOT sub-base per tonne

Edging per linear metre

Pegs each

Labour cost

Rate x total area

Delivery (flat fee)

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Results

Total Area
-
m²

Grid panels
-
panels

Gravel to order
-
tonnes

Perimeter

linear m

Area Breakdown

Area	Dimensions	Area (m²)	Panels	Gravel (t)	Perimeter (m)

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Frequently Asked Questions

How many gravel stabilisation grid panels do I need?

Divide area by the area of one panel. A typical panel is 600 x 400 mm (0.24 m²). A 30 m² driveway: 30 ÷ 0.24 = 125 panels + 5-10% cutting waste. Gravel infill: approximately 20-25 kg/m² for a 50 mm grid depth using 10-20 mm aggregate.

What gravel should I use to fill stabilisation grids?

Use angular or crushed stone (10-20 mm) - not smooth rounded pea gravel. Angular stone locks together and resists displacement. Popular: crushed granite, limestone, or flint. Decorative coloured gravels also work. Avoid stones over 20 mm - they sit proud of the grid and become a trip hazard.

What sub-base do I need under a gravel grid?

Pedestrian path: 50-100 mm compacted MOT Type 1 or Type 3 + geotextile membrane. Car driveway: 150 mm Type 1. Heavy vehicles: 200 mm Type 1. Lay a weed membrane over the sub-base (under the grids) to prevent weed growth from below without blocking drainage.

Is a gravel grid driveway classed as a permeable surface?

Yes - gravel grids are permeable surfaces so paving a front garden with them does not require planning permission regardless of area, under the 2008 GPDO. Solid impermeable surfaces (concrete, tarmac) require permission for front gardens over 5 m². Gravel grids are also SuDS-compliant.

Can gravel grids be driven on by cars?

Most standard grids are rated for domestic vehicles (up to 3.5 tonnes per axle). Heavy-duty grids are available for HGV/commercial use. Check the manufacturer's load rating. For car use: a 50 mm grid on 150 mm Type 1 sub-base is standard. A thinner grid or inadequate sub-base causes flex and gravel migration.

How do I prevent gravel from spreading or migrating?

Gravel grids are the best solution - cells hold aggregate in place under traffic. At the perimeter: use a solid edging (timber, metal, or concrete kerb) to contain the grids. Fill gravel to the top of the grid for a stable flush surface. Do not overfill - gravel proud of the grid is unstable and will spread. Rake level periodically.

Grid depth	Best for
30 mm	Light foot traffic, garden paths
40 mm	Standard driveways, parking (most popular)
50 mm	Heavy vehicles, commercial use
60 mm	HGV access, lorry parking

Grid depth

Best for

30 mm

Light foot traffic, garden paths

40 mm

Standard driveways, parking (most popular)

50 mm

Heavy vehicles, commercial use

60 mm

HGV access, lorry parking

Gravel Stabilisation Calculator

How many gravel grid panels do I need?

Gravel Stabilisation Calculator

Areas

Job Costing (optional)

Results

Area Breakdown

Cost Estimate

Frequently Asked Questions

Grid Selection Guide

Gravel Choice

Installation Tips

Reviews

Gravel Stabilisation Calculator

How many gravel grid panels do I need?

Gravel Stabilisation Calculator

Areas

Job Costing (optional)

Results

Area Breakdown

Cost Estimate

Frequently Asked Questions

Grid Selection Guide

Gravel Choice

Installation Tips

Reviews

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