Roadbase for a Driveway
Calculate the roadbase needed for a solid driveway foundation.
Calculate Your Road Base
Recommended depth: 100-150mm for driveways
Total Volume
Building a Solid Driveway Foundation
A well-constructed driveway starts with a properly prepared roadbase foundation. Whether you're finishing with concrete, asphalt, pavers, or even leaving the roadbase as the final surface, this compacted base layer is what gives your driveway its structural integrity. For a standard single-car driveway of 10 metres by 3 metres at 150mm depth, you'll need approximately 4.5 cubic metres of DGB20 roadbase. This weighs around 8.1 tonnes, a substantial delivery that requires proper truck access to your property.
The 150mm depth provides adequate support for regular passenger vehicles on most soil types. Driveways on soft clay soils or those expecting heavier vehicles like caravans or trailers may benefit from 200mm depth. On stable, well-compacted subsoils, 100mm can be sufficient, though the additional cost of going thicker is usually worthwhile insurance against future problems.
Why DGB20 Is the Standard Choice
DGB20, or Dense Graded Base with 20mm maximum particle size, is the most commonly specified roadbase for residential driveways. The blend of particle sizes from dust through to 20mm stones allows the material to compact into a dense, interlocking mass. When properly compacted with a vibrating plate or roller, DGB20 creates a stable surface that distributes vehicle weight effectively and resists rutting and erosion.
Compaction Is Critical
The weight and volume calculated above assumes loose material as delivered. During compaction, roadbase reduces in thickness by roughly 20 to 25 percent. This is accounted for by specifying your target compacted depth when ordering. If you want a finished depth of 150mm after compaction, the material is spread somewhat thicker and compacted down. A plate compactor is adequate for residential driveways, with multiple passes at optimal moisture content achieving the density needed for long-term performance.
For gravel as the final surface, see our gravel driveway calculator. Use our main roadbase calculator for custom dimensions.