Garden guide
Patio Sub-Base: How Deep and What Material?
The short version
Patios need 10cm of compacted MOT type 1 under the bedding layer; driveways need 15cm. Skip it or skimp it and you'll be re-laying rocking slabs within a couple of years — almost every failed patio traces back to the sub-base.
What MOT type 1 actually is
Crushed limestone (or granite) graded from 40mm down to dust. The mix of sizes is the point: it compacts into a near-solid, load-spreading layer that still drains. Crusher run and scalpings are the cheaper cousins — fine under patios on firm ground.
Compaction is everything
Loose-tipped hardcore settles for years. Lay it in 5cm layers and run a wacker plate over each until the surface stops moving — a day of wacker hire is the best money in the whole project. Check your levels and drainage fall as you build up, not after.
How much to order
Area (m²) × depth (cm) × 10 = litres, and MOT type 1 runs about 2 tonnes per cubic metre. A 12m² patio at 10cm needs 1.2m³ — roughly two bulk bags. Order 10% extra: compacted material takes up less room than loose.
Then the bedding layer
On top of the sub-base goes 5cm of sharp sand (or a full mortar bed) for the slabs to sit on. Our sand calculator works out the bedding quantity from your patio area.