Base Rock
Also known as: Class 2 base, road base, aggregate base, AB, 3/4 minus
Base rock is a blend of crushed angular stone and fine particles ("fines") that compacts into a hard, stable foundation. It is the layer that goes under pavers, concrete, driveways and pathways.
In simple terms
Base rock is crushed rock with the dust left in. The mix of chunky and fine pieces locks together when compacted, creating a solid, load-bearing base that won’t shift under what you build on top.
In depth
Often called Class 2 aggregate base or "3/4 minus," base rock is engineered with a graded particle distribution from 3/4 inch down to dust. The fines fill the gaps between larger stones so that, once moistened and compacted, the layer reaches high density and bearing strength. It is placed in compacted lifts of 2–4 inches. Unlike drain rock, base rock is meant to pack tight — it is not for drainage.
Why it matters
A properly compacted base prevents the cracking, settling and heaving that ruin patios, walkways and driveways — it is the single most important layer in a hardscape installation.
Common mistakes
- Using base rock where drainage is needed — its fines block water flow.
- Not compacting in thin lifts or skipping the plate compactor, leaving a soft base that settles later.
Examples & uses
- Sub-base under paver patios and walkways.
- Foundation layer for concrete slabs and footings.
- Driveway and parking-pad base.