The depth of crusher run is one of the most consequential decisions in any driveway, base layer, or patio project. Too shallow and the surface will rut, settle, or fail under load faster than it should. Too deep and you are paying for material that adds no practical benefit.
The correct depth depends on what the crusher run is being used for, what is going on top of it, and the bearing capacity of the native soil beneath it. This guide gives the standard depth recommendations for the most common residential applications, with a reference table for quick planning.
The Difference Between Loose Depth and Compacted Depth
Before getting to the numbers, one important clarification. Crusher run depth is almost always stated as a compacted depth, meaning the depth of the layer after compaction has been completed. Loose crusher run compacts by roughly 20 to 25 percent under a plate compactor.
This means that to achieve a 4-inch compacted depth, you need to spread approximately 5 to 6 inches of loose material. To achieve a 2-inch compacted surface layer, spread approximately 3 inches of loose material.
Always plan your excavation depth and material quantity based on the compacted target, then account for the loose-to-compacted ratio when calculating how much to dig out and how much to order. Our crusher run quantity guide walks through the full calculation including the compaction factor.
Depth for Driveway Use
A residential driveway built with crusher run performs best as a two-layer system: a compacted base layer that handles the structural load and a compacted surface layer that provides the finished driving surface.
Base layer: 4 inches of compacted crusher run is the standard minimum for a residential driveway on firm, well-draining native soil. On soft or clay soils, or for driveways that carry heavy vehicles such as trucks or RVs, increase the base layer to 6 inches of compacted depth.
Surface layer: 2 inches of compacted crusher run is sufficient as a surface layer over a correctly compacted base. This layer provides the tight, fine-finished surface that gives crusher run driveways their stability underfoot.
Total depth: 6 inches of compacted material is the standard residential minimum. 8 inches is recommended for soft soils or heavy vehicle use.
The full installation sequence for a two-layer driveway is covered in the crusher run driveway installation guide.
Depth for Patio Base Use
When crusher run is used as a base layer under a patio surface material such as pea gravel, flagstone, or pavers, depth requirements are slightly less than for a vehicle-traffic driveway because the load is lower.
Under pea gravel: 4 inches of compacted crusher run base is a solid foundation for a pea gravel patio on firm soil. If the soil is soft or the patio will have heavy outdoor furniture, 6 inches provides a more stable platform. For pea gravel patio depth requirements generally, the pea gravel patio guide covers the full installation approach.
Under flagstone: 4 inches of compacted crusher run is standard. The flagstones distribute load across the surface, so the base layer depth requirement is comparable to the pea gravel application.
Under pavers: Paver manufacturers typically specify a minimum compacted aggregate base depth. A common specification is 4 to 6 inches of compacted base, with 6 inches on softer soils. Crusher run performs well as a paver base because its fines compact into a level platform that supports the paver bedding layer above it. For paver-specific base guidance, the driveway base requirements guide covers the full layering sequence.
Depth for Shed Base Use
A crusher run shed base requires enough depth to distribute the shed’s weight evenly and prevent the corners and edges from sinking over time.
Standard shed on firm soil: 4 inches of compacted crusher run is adequate for a small to medium shed on firm, well-draining soil.
Larger shed or soft soil: Use 6 inches of compacted crusher run. This is particularly important for larger sheds where uneven settlement at the corners would cause structural problems for the building above.
The crusher run shed base guide covers the shed-specific installation in full, including whether a membrane and edging are required.
Depth for Sub-Base Under Concrete
When crusher run is used as a sub-base beneath a concrete slab, the depth is governed partly by the slab specification and partly by the soil conditions.
Light-use residential slab (garden shed, small outbuilding): 4 inches of compacted crusher run sub-base is standard on firm soil.
Vehicle-traffic slab (garage floor, parking pad): 6 inches of compacted sub-base is typically specified. On soft soils, a geotextile separator between the native soil and the crusher run helps prevent the sub-base from mixing into the ground below it over time.
Note that when crusher run is used under concrete, drainage behavior differs from its use as a standalone driveway surface. For a full discussion of how crusher run handles water in sub-base applications, the crusher run drainage guide covers the permeability considerations.
Quick Reference Depth Table
| Application | Compacted Base Depth | Compacted Surface Layer | Total Compacted Depth |
|---|---|---|---|
| Residential driveway, firm soil | 4 in | 2 in | 6 in |
| Residential driveway, soft/clay soil | 6 in | 2 in | 8 in |
| Heavy vehicle driveway | 6 in | 2 in | 8 in |
| Patio base under pea gravel | 4 in | n/a | 4 in |
| Patio base, soft soil | 6 in | n/a | 6 in |
| Paver base | 4 to 6 in | n/a | 4 to 6 in |
| Shed base, small shed | 4 in | n/a | 4 in |
| Shed base, large shed or soft soil | 6 in | n/a | 6 in |
| Sub-base under concrete, light use | 4 in | n/a | 4 in |
| Sub-base under concrete, vehicle traffic | 6 in | n/a | 6 in |
How Soil Type Affects Depth Decisions
The bearing capacity of the native soil is the variable that most often requires you to increase depth beyond the standard minimum. If the soil beneath your project compresses or moves easily, a thin base layer will not distribute the load across a wide enough area to prevent settlement.
The simple field test for soil bearing capacity is to push a standard screwdriver into the soil by hand. If it sinks easily to the full length of the blade, the soil is soft and the deeper end of the depth range applies. If it resists at 2 to 3 inches, the soil has reasonable bearing capacity and the standard minimum depth is appropriate.
Clay soils are particularly prone to volume change with moisture. In wet conditions clay expands; in dry conditions it contracts. A base layer of at least 6 inches of compacted crusher run over a geotextile membrane provides a more stable platform over clay than the standard 4-inch minimum.
Frequently Asked Questions
How deep should crusher run be for a driveway?
For a residential driveway, a total compacted depth of 6 to 8 inches is standard. This is typically a 4-inch compacted base layer plus a 2-inch compacted surface layer. Driveways on soft or clay soils, or those carrying heavy vehicles, should use the deeper end of this range.
How deep should crusher run be for a patio base?
For a patio base under pea gravel or flagstone, 4 inches of compacted crusher run is the standard minimum. On softer soils, 6 inches provides a more stable foundation. The patio surface material goes on top of the compacted crusher run layer.
How deep should crusher run be under concrete?
When used as a sub-base under a concrete slab, crusher run is typically placed at 4 to 6 inches of compacted depth. The correct depth depends on the slab thickness, the intended load, and the bearing capacity of the native soil.
Does crusher run depth change on soft or clay soil?
Yes. On soft, wet, or clay-heavy soils, add 2 inches to the base layer depth in all applications. Clay soils are more susceptible to movement and moisture-related settlement, and a deeper base layer provides better load distribution and reduces the risk of surface instability over time.