Everything You Need to Know About CA6 Gravel: Selection, Quantity, Cost, and Installation

CA6 is useful when a project needs a compacted, load-spreading layer rather than loose, free-draining stone.

1. Driveway and parking-area base: CA6 can form part or all of a base section for a gravel driveway or beneath a finished driveway surface, provided the depth and drainage design suit the soil and vehicle loads.
2. Patio, paver, and walkway base: A compacted CA6 layer can create a stable platform below bedding material and pavers.
3. Road, pavement, and slab subbase: It may be specified beneath pavements or slabs to provide a firm, level working base. The complete slab or pavement section must suit the actual loads, soil, moisture conditions, and applicable design requirements; ordinary retail CA6 is not automatically appropriate beneath every slab.
4. Backfill and grading: It may be appropriate where plans or local specifications call for compactable aggregate backfill.
5. Bare aggregate surfaces: CA6 can be used as a finished utility surface, but its fines can track, dust, or soften if drainage and maintenance are poor.

Do not assume retail CA6 is suitable for concrete. Concrete aggregate and mix proportions must meet the concrete producer’s or engineer’s requirements; use CA6 in concrete only when that exact material has been approved for the mix.

• Compaction: Its range of particle sizes allows the aggregate to interlock into a firm layer.
• Load distribution: A properly compacted base spreads loads over the prepared subgrade instead of concentrating them in soft spots.
• Availability: CA6 or a comparable dense-graded base is widely sold in many areas, including recycled-concrete versions from some suppliers.
• Flexible use: It can serve as the compacted base itself; a separate coarse-stone layer is not automatically required.

Its limitations matter too. Because CA6 includes fines, compacted CA6 has less connected void space than open-graded stone. Do not rely on it alone to solve standing water, groundwater, French-drain, or retaining-wall drainage problems.

Proper CA6 Gravel Installation: A Step-by-Step Guide

Before ordering material, decide whether CA6 is the base layer, a finished gravel surface, or part of a larger paver, asphalt, or concrete section. Required depth depends on soil strength, drainage, slope, frost exposure, traffic, and the surface above it. Related guidance: Diy Guide: Installing a Ca6 Gravel Base for a Compact, Low-Maintenance Driveway.

Planning starting points only—confirm locally

The table below gives preliminary compacted CA6-layer depths for early DIY quantity planning, not universal design requirements. Weak or wet soil, freeze-thaw exposure, slopes, heavy vehicles, and the complete pavement assembly can require a different section. Confirm the final depth with local requirements, a qualified installer, or an engineer where performance matters.

For surface drainage, a 1–2% slope away from structures is a planning starting point, not a universal requirement. That is a drop of about 1–2 feet in 100 feet. Establish the actual slope with string lines, a level, or a laser, and direct runoff to an approved location without affecting adjacent property.

Call 811 before any excavation, wait for the required utility markings, and identify private lines that may not be included in public locating. Check local requirements for driveway entrances, culverts, grading, runoff, impervious-area limits, and permits. Wear gloves, sturdy footwear, eye protection, hearing protection when using a compactor, and a properly selected dust respirator when dry aggregate creates airborne dust. Lightly mist excessively dry material if needed to control dust; do not create muddy runoff or compact saturated aggregate.

• 1. Lay out and excavate: Mark the finished edges, elevations, and drainage direction with stakes and string. Remove vegetation, topsoil, roots, loose material, and soft organic soil. Excavate for the full planned base section and finished surface—not to a generic depth.
• 2. Shape and check the subgrade: Grade the exposed soil to the intended drainage path before aggregate goes down. Compact a stable subgrade. Do not work a saturated, muddy, or pumping subgrade. Small isolated soft spots should be excavated and corrected before proceeding; do not bury them under more aggregate.
• 3. Use separation fabric only when needed: A permeable geotextile separator can help keep weak or fine native soil from mixing into the aggregate. Its primary role is separation or stabilization, not dependable weed control. It does not replace correction of unstable soil or a drainage design. Use project-appropriate fabric rather than plastic sheeting that can trap water.
• 4. Choose the base arrangement: CA6 alone is often used as the compacted base where subgrade is stable and drainage is adequate. An open-graded drainage layer may be part of a designed system, but it needs separation and a place for water to exit. Do not add coarse stone beneath CA6 by default.
• 5. Place CA6 in lifts: Spread manageable loose lifts about 2–3 inches thick for small DIY work, then compact each lift before adding the next. This loose thickness is a practical starting point, not a substitute for the project specification or the compactor manufacturer’s capability. For thicker or wider base work, follow the specified lift thickness and equipment requirements.
• 6. Moisture-condition and compact: Lightly moisten very dry, dusty aggregate only as needed. Never compact saturated material. Use a plate compactor for many small paths and patios; wider or thicker driveway work may require a reversible plate compactor or roller. Make overlapping passes in more than one direction. For specified work, follow the required equipment, lift thickness, and density testing.
• 7. Finish-grade and contain the surface: Check elevation and slope with a level, string line, or straightedge. Install edging where it is needed to hold a bare gravel surface or define a paving area. The finished compacted layer should feel firm and show no rutting, rocking, pumping, or visible movement under equipment.

Inspect the area after the first heavy rain, snowmelt, or freeze-thaw cycle. Correct low spots and runoff paths early. For a bare CA6 surface, rake displaced material back into place and add material only after correcting the cause of erosion or settlement.

Preparing Your Site for CA6 Gravel Installation

Preparation determines whether the base stays level. Keep the excavation free of topsoil and roots, establish drainage before placing aggregate, and correct weak spots instead of burying them under more stone. Stop and seek professional help if excavation exposes utilities, groundwater, unstable soil, contaminated material, a steep or failing slope, retaining-wall risk, or drainage that affects a neighboring property.

Excavation: Preparing the Ground for CA6 Gravel Installation

Measure depth from the intended finished elevation, allowing for every layer in the assembly. Keep the excavation consistent, but do not create a flat basin that traps water. A compacted CA6 layer is only one part of the system: a failed subgrade, blocked outlet, or poor surface slope cannot be corrected simply by adding more CA6.

Using a Weed Barrier for a Low-Maintenance Gravel Surface

A permeable geotextile may be useful as a separation layer over weak soil, and it can limit some growth from below. It will not prevent windblown seeds from germinating in surface debris. Overlap and secure fabric according to the manufacturer’s instructions, keep it smooth, and avoid leaving it exposed where it can tear or become a tripping hazard.

Creating a Solid Foundation with a Base Layer for CA6 Gravel

CA6 is commonly the solid, compactable base layer. Use a separate open-graded aggregate layer only when the project design needs drainage, separation, or another function that CA6 cannot provide. Open-graded aggregate must be selected and detailed as a system; it is not interchangeable with CA6 simply because both are crushed aggregate.

Differences Between CA6 and CA7 Gravel

What Are the Size Specifications of CA6 Gravel?

Supplier descriptions sometimes summarize CA6 as aggregate ranging from larger crushed particles down to fines, including the shorthand “3/4 inch down to dust.” Treat that as a local description, not a universal specification. The maximum size, percentage of fines, source material, and recycled content can differ by location and project.

The fines fill spaces between larger particles during compaction and help create the dense, stable layer that makes CA6 useful as a base. They also mean the material is not the same as free-draining stone.

Installation Depth & Layering

Use the planning table above only to begin estimating. The required compacted depth for a driveway, patio, path, or pavement must account for soil, drainage, traffic, frost, slope, and the finished surface. Install the selected depth in compactable loose lifts, not as one deep loose layer.

Regional Variations & Comparison

Ask for a gradation sheet, product name, intended application, recycled-content disclosure if relevant, and the supplier’s bulk-density or tons-per-yard conversion. This is especially important when comparing CA6 with CA7, #57 stone, #89 stone, or other local names.

What Is the Pricing for CA6 Gravel?

CA6 is commonly quoted by the ton, cubic yard, or delivered load. Do not use a generic ton-to-yard conversion: aggregate density and moisture vary, so use the supplier’s current conversion factor.

For a planning estimate, calculate the compacted volume first:

• Area in square feet = length × width.
• Depth in feet = compacted depth in inches ÷ 12.
• Compacted cubic feet = area × depth.
• Compacted cubic yards = cubic feet ÷ 27.
• Convert yards to tons only with the supplier’s stated factor.
• Add a clearly labeled 10–20% planning allowance for grading loss, handling, and compaction unless the supplier or project specification provides a better allowance.

Worked quantity example

Example only: A 20-foot by 10-foot patio base is planned at a 4-inch compacted CA6 depth.

1. Area: 20 ft × 10 ft = 200 square feet.
2. Depth: 4 inches ÷ 12 = 0.333 foot.
3. Compacted volume: 200 sq ft × 0.333 ft = 66.7 cubic feet.
4. Convert to cubic yards: 66.7 ÷ 27 = 2.47 cubic yards.
5. If the supplier states that its CA6 weighs 1.5 tons per cubic yard, the compacted quantity is 2.47 × 1.5 = 3.71 tons. This factor is hypothetical; use the supplier’s factor for the actual material.
6. Add a planning allowance. With a 15% allowance, 3.71 × 1.15 = 4.27 tons. Round the order according to the supplier’s sale unit and minimum load—for example, 4.3 tons if partial-ton sales are available.

The 15% allowance in this example is a planning allowance, not a guaranteed compaction percentage. Actual yield varies with the aggregate, moisture, handling, lift thickness, and supplier measurement method.

Worked delivered-cost example

Hypothetical quote only: Using the 4.3-ton example order, assume a supplier quotes CA6 at $32 per ton, delivery at $95, a $15 fuel or minimum-load fee, and 8% tax on the material charge. The project total would be calculated as follows:

• Material: 4.3 tons × $32 = $137.60
• Delivery: $95.00
• Fuel or minimum-load fee: $15.00
• Tax, if applicable: 8% × $137.60 = $11.01
• Estimated delivered total: $258.61

This is a calculation example, not a price estimate. Request a written quote that identifies the exact material and gradation, price unit, whether the load is certified by weight or estimated by volume, delivery charge, minimum order, taxes, fuel or environmental fees, and whether spreading is included.

Where to Find CA6 Gravel Suppliers Near You

Contact local aggregate yards, quarries, landscape-material suppliers, or contractors familiar with your area’s specifications. Give each supplier the same project dimensions, intended use, and delivery location so quotes are comparable.

• Ask whether the material is CA6 under a local or state specification and request its gradation information.
• Confirm whether the material is virgin or recycled and whether that matters for project requirements.
• Ask for the supplier’s weight-per-yard conversion instead of estimating it yourself.
• Confirm truck access, delivery placement, and whether the driver can safely dump at the intended location.

If the project is a structural driveway, public-road connection, retaining wall, or major drainage installation, confirm the aggregate and complete base design with the responsible local authority, contractor, or engineer before delivery.

What Influences the Price of CA6 Gravel?

The material price is only part of the budget. Hauling distance, minimum-load charges, fuel surcharges, quantity, material source, taxes, site access, and placement service may have as much effect on a small project as the per-ton price. Compare delivered totals and matching material specifications—not just the lowest unit price.

Best Practices for Using and Maintaining CA6 Gravel

1. Keep water moving as designed: Maintain the planned grade, clean nearby drains or outlets, and investigate recurring puddles rather than adding fines-containing aggregate over them.
2. Repair failures at their source: Pumping, rutting, or repeated low spots usually indicate wet or weak subgrade, poor drainage, insufficient support, or inadequate edge restraint. Remove failed material, correct the underlying condition, and rebuild in compacted lifts.
3. Inspect after weather events: Check bare gravel surfaces after heavy rain, snowmelt, and freeze-thaw. Regrade displaced material and replenish only when the compacted layer or surface has genuinely been lost.
4. Keep edges supported: Repair damaged edging before aggregate spreads into lawns or planting beds.

Open-graded aggregate is generally used where a pavement system must pass water through connected voids; materials with more fines serve a different structural role. University of Nevada Extension’s porous-pavement guidance explains why aggregate gradation and the complete drainage design matter.

Conclusion

CA6 is a locally specified, dense-graded aggregate valued for compaction and base stability. It is a practical choice beneath driveways, paths, patios, and pavements when the subgrade, thickness, slope, and drainage are appropriate. Related guidance: How to Choose Between Ca6 and #57 Gravel for Your Driveway: a Practical Comparison and Decision Guide.

Confirm the local product specification, use a project-appropriate compacted depth, calculate quantity from compacted volume, place it in compacted lifts, and use open-graded stone only where a drainage design calls for it. Those steps matter more than relying on a generic material name.

FAQ

How can I improve drainage when using CA6 gravel?

Start with proper surface slope, stable subgrade, and a clear runoff path. CA6 is not free-draining drainage stone once compacted. If the project needs a French drain, retaining-wall drainage zone, or infiltration system, use the open-graded aggregate, filter separation, and outlet specified for that system.

What common mistakes should I avoid when installing CA6 gravel?

Avoid placing one deep loose lift; compacting saturated or pumping material; burying soft spots; assuming a coarse-stone layer is always needed; using CA6 as drainage stone; and converting tons to yards without the supplier’s factor.

Are there specific tools recommended for working with CA6 gravel?

Useful tools include stakes and string, a shovel, rake, wheelbarrow, level or straightedge, tape measure, water source for light moisture conditioning, and a plate compactor. Larger driveway work may need a reversible plate compactor, roller, skid steer, or contractor rather than hand tools.

How do I know if I need to replenish or replace my CA6 gravel?

Regrade or add material when erosion, traffic, or weather has removed the surface or created low spots. If the layer ruts, pumps, rocks, or repeatedly settles, remove the failed area and correct drainage or weak subgrade before replacing and compacting CA6.