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Guide
How to lay a sub-base for a patio or driveway
How deep to dig, which sub-base to use, and how to compact it for patios, paths and driveways that stay level.
Why the sub-base matters
Most sinking and rocking paving comes from a weak base, not from the slabs or blocks. A well-compacted sub-base spreads the load and drains water away, so the surface stays level.
How deep to go
Depths depend on the ground and the use. As a rough guide, patios and paths often use around 100 mm of compacted sub-base, while driveways that take cars need considerably more. Allow for the sub-base, the bedding layer and the paving itself when you dig out.
Choosing and laying the material
MOT Type 1, a crushed stone with fines, is the usual sub-base because it compacts into a solid layer. Lay it in layers rather than all at once and compact each layer with a plate compactor, working across the area more than once.
Finish with a bedding layer of sharp sand for block paving, or a mortar bed for patio slabs, then lay the surface with a slight fall so water runs off.
Frequently asked questions
What is MOT Type 1?
A graded crushed stone sub-base that includes fine material, so it compacts into a firm, load-bearing layer.
Do I need a membrane under the sub-base?
A geotextile membrane is often laid on soft or clay ground to stop the sub-base mixing into the soil below and to help keep weeds down.
How do I stop a patio sinking?
Dig to firm ground, use enough sub-base for the load, compact it thoroughly in layers, and bed the paving properly.