What Type of Gravel Should Be Used for Patio Stones?

Small Gravel

• Small gravel contains crushed rocks that are about 3/8-inch large and mixed with stone dust. The advantage of small gravel is that it compacts into a firm, almost solid surface. A 4-to-6-inch layer of small compacted gravel can support a stone patio with a high volume of foot traffic and heavy furniture. Use small gravel only if drainage is not a concern. Water runoff does not drain well through this type of base. Poor drainage creates small pools beneath the stones, which causes them to buckle or heave.

Medium Gravel

• Medium gravel measures from 1/2 to 3/4 inch. It contains irregularly shaped crushed rocks with sharp edges that can pack tightly together. The larger rocks create narrow gaps that allow underground water to escape. A 6-to-8-inch layer of medium gravel is strong enough to support even the heavy loads of driveway pavers. Plan to cover the gravel with a 1-inch layer of sand to create a flat, smooth base for the patio stones.

Large Gravel

• Rocks crushed into 1 1/2-inch pieces and larger are typically used to pave driveways, parking lots and surfaces that must support a high volume of traffic. The large rocks compact but not as solidly as medium gravel. If the patio site is in an area with poor drainage, dig a 10-inch-deep foundation and lay a 4-inch layer of large gravel beneath the medium gravel base to improve the site's drainage.

Recycled Concrete

• Recycled concrete is affordable, and using it conserves natural resources. Concrete from old driveways, sidewalks and buildings is separated from steel and other materials and crushed into gravel. It breaks down into irregular shapes of different sizes that compact as tightly as medium gravel. The smallest pieces break down into a powder but do not compact as solidly as small gravel, allowing water to escape.