What is the best sub-base for a patio?

Crusher run (also called processed gravel or road base) is the best general-purpose sub-base material for patios. It combines angular crushed stone particles with fine material that compacts tightly, provides stable load distribution, and drains well. It is suitable under gravel, pavers, flagstone, and concrete surfaces.

Can I use sand as a patio base?

Sharp sand (coarse sand) can be used as a bedding layer directly beneath pavers or flagstones, but it should not be used as the primary sub-base layer. Sand does not compact well enough to provide stable load distribution and is prone to washing out under heavy rain.

What crushed stone size is best for a patio sub-base?

3/4-inch crushed stone (also known as #57 stone) is the most widely recommended sub-base aggregate for patios. It provides good drainage, compacts well with a plate compactor, and interlocks effectively to resist lateral movement.

Best Base Material for a Patio

The sub-base material used in a patio base layer determines how well the patio drains, how stable it is under load, and how well it performs through freeze-thaw cycles. Choosing the right material for your specific surface type and site conditions is one of the most impactful decisions in the entire installation process.

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What Makes a Good Sub-Base Material

An effective patio sub-base material must do three things well: compact tightly to resist settling and lateral movement under load; drain freely so that water does not accumulate beneath the surface; and resist frost heave by not retaining moisture that would freeze and expand in winter.

Angular crushed stone consistently outperforms rounded aggregate for sub-base use because angular particles interlock when compacted, while rounded particles tend to roll and shift under load. This interlocking behavior is the reason that crusher run, which contains both angular stone particles and fine material, is the most widely specified sub-base aggregate for patios and driveways alike.

For a detailed guide to crushed stone grades and how they are classified by size, our crushed stone size chart explains the grading system used by suppliers, which directly informs sub-base aggregate selection.

Sub-Base Materials Compared

Crusher Run (Processed Gravel / Road Base)

Crusher run is the most versatile and widely available patio sub-base material. It consists of crushed stone particles in a range of sizes from 3/4-inch down to fine stone dust, all of which interlock and compact tightly when a plate compactor is used. Crusher run is suitable as a sub-base under all patio surface types and on all but the most difficult soil conditions.

Cost: typically $25 to $45 per ton. Coverage: approximately 100 square feet at 3-inch depth per ton, depending on compaction ratio.

Best used under: pavers (dry laid), flagstone (dry laid), concrete, and as a sub-base layer under gravel patios on clay soils.

3/4-Inch Crushed Stone (#57 Stone)

Clean 3/4-inch crushed stone (also called #57 or washed stone) compacts well and drains excellently. Unlike crusher run, it contains no fines, which means drainage is faster but compaction is slightly less tight. It is an excellent choice for sites with drainage problems or high water tables, where the sub-base needs to act as a drainage reservoir rather than just a structural layer.

Cost: typically $30 to $50 per ton. Best used under: gravel patios on clay or poorly draining soil; paver and flagstone patios on sites with drainage concerns.

Stone Dust (Decomposed Granite Fines)

Stone dust is used as a bedding layer directly beneath pavers and flagstones, not as a primary sub-base material. Its very fine particle size creates a dense, smooth bed that allows individual paver units to be adjusted and set precisely. However, stone dust compacts poorly when wet and can wash out of the joint area over time. It should always be placed on top of a compacted crushed stone sub-base, never as a replacement for it.

Best used as: a 1 to 2-inch bedding layer directly under dry-laid pavers or flagstone.

Sharp Sand (Coarse Sand)

Sharp sand is an acceptable bedding layer alternative to stone dust for paver installation. It is easier to source in most areas and slightly more forgiving to work with during the leveling process. It has the same limitations as stone dust — it should not be used as a primary sub-base material and must be placed on a compacted crushed stone sub-base layer.

Best used as: a 1-inch bedding layer directly under pavers. Not suitable as a primary sub-base.

Recycled Crushed Concrete

Recycled crushed concrete (also called Class II aggregate or recycled base) performs similarly to virgin crusher run in compaction and drainage behavior, and it is often available at lower cost. It is suitable for use as a primary sub-base under any patio surface type. One consideration: recycled concrete can have variable particle size depending on the crushing process — confirm with the supplier that the material is processed to a consistent grade before ordering.

Choosing by Surface Type

Surface	Primary Sub-Base	Bedding Layer
Pea gravel / loose gravel	3/4-inch crushed stone or crusher run	None
Concrete pavers (dry laid)	Crusher run or 3/4-inch crushed stone	1 in. sharp sand or stone dust
Flagstone (dry laid)	Crusher run or 3/4-inch crushed stone	1-2 in. stone dust
Concrete slab	Crusher run or 3/4-inch crushed stone	None
Flagstone (wet laid / mortared)	Crusher run sub-base + poured concrete	0.5 in. mortar

Calculating How Much Sub-Base You Need

To calculate the quantity of sub-base material required: multiply the patio length in feet by the width in feet by the sub-base depth in feet, then divide by 27 to get cubic yards. Multiply by 1.4 to convert cubic yards to tons (approximate conversion for crushed stone). Add 10% for compaction and spillage.

For example: a 12 x 16-foot patio with a 4-inch (0.33-foot) sub-base layer requires 12 x 16 x 0.33 = 63.4 cubic feet, divided by 27 = 2.35 cubic yards. Multiplied by 1.4 = approximately 3.3 tons. With 10% overage = 3.6 tons to order.