What Is a Sub-Base?
Written by James Walker · Last reviewed 15 August 2026
James Walker has 2 degrees in construction (BSc (Hons) Building Surveying · MSc Environmental Design of Buildings) and an extensive background in issue resolution, resolving over £4 billion of consumer issues.
A sub-base is the layer of compacted crushed stone laid beneath a driveway, patio or path. It spreads load and provides the stable foundation that the visible surface sits on.
Why it matters more than the surface
Because it determines how long the surface lasts.
A driveway on an adequate, properly compacted sub-base survives years of vehicle loading. The same surface on a thin or poorly compacted one cracks, sinks and ruts, usually within a few years, and always after the contractor has been paid.
The problem with it
It is completely invisible once the surface goes down.
That makes it the easiest thing in home improvement to skimp on without detection, and it is the main reason a very cheap driveway quote is cheap. Less excavation, less stone, less compaction, a lower price and a shorter life.
How to protect yourself
Ask what depth is being laid and how it is compacted. Then build a payment stage at sub-base complete, and ask for it to be photographed before surfacing.
That single stage is the only opportunity to verify the part you are actually paying for.
How it works
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