A compactable angular aggregate is a common parking-pad base choice, but the surface and thickness need to match the actual ground and loads. American Rock Supply recommends road base with a clean #57 cap; Hello Gravel describes a fines-bearing road-base system.1, 2 Those supplier recipes are not a universal design. A pickup, trailer or RV label alone does not establish adequate support, and gravel quantity does not prove capacity.
Material choices by role
| Role | Possible material | Check before ordering |
|---|---|---|
| Base | Specified dense-graded road base or crusher run. | Full gradation, source material, quality and required installed condition. |
| Exposed surface | A selected fines-bearing mix or another specified finish. | Traffic, walking comfort, movement and maintenance needs. |
| Clean aggregate layer | A clean/angular product such as supplier #57 where the system calls for it. | Not automatically interchangeable with a fines-bearing driving mix. |
| Separation or stabilization | A specified geotextile, grid or confinement system when needed. | Structural function, drainage compatibility and installation requirements. |
| Jack/support locations | Ground and support system suitable for the actual concentrated loads. | Vehicle/support manufacturer requirements and site bearing capacity. |
Supplier names vary. Ozinga lists CA6 in limestone and recycled-concrete variants, with several regional labels.3 A similar name or color does not prove an identical product. Ask for current gradation and quality documentation rather than choosing only a nominal size.
Ground, water and loads decide the plan
- Inspect soft/wet ground, existing fill, slope and drainage outlets. FHWA links gravel-road performance to subgrade strength, aggregate depth, loading, material quality and drainage.4 Its road context is a planning reference, not a pad design.
- Identify loaded vehicle weights, axle loads, turning frequency and long-term parking conditions. Do not interpret a vehicle class name as a structural specification.
- Plan concentrated jack, landing-gear or stabilizer locations separately. A surface that supports tires does not automatically approve every support footprint.
- Check boundaries, setbacks, drainage easements and local permits before construction. Hello Gravel explicitly tells readers to check municipal requirements.2
- Before excavation in the U.S., contact 811, wait the required time, confirm all responses and dig carefully around the marks.5 Determine whether private lines require separate locating.
RVs and trailers: support ratings are not soil ratings
Use the actual vehicle and support-system instructions for leveling, chocking and support. As one manufacturer example, Andersen publishes different ratings for its 4-inch and 8-inch jack blocks and lower limits when stacked.6 That illustrates why neither a generic block name nor a pad-depth chart establishes a safe setup. A block rating also does not establish the bearing capacity of the gravel and soil below it. This guide does not select jack blocks, certify a support footprint or approve lifting a vehicle.
Do not copy a vehicle-depth chart as a design
American Rock Supply gives selected base depths by vehicle category and describes 2-inch placement lifts. Hello Gravel gives a 6-8-inch total-depth recipe for its pad product.1, 2 Those are supplier suggestions with different assumptions, not a verified design for your loaded RV or weak clay ground. Have the project establish layer thickness, compaction equipment, lift thickness, moisture and acceptance requirements. Heavy or concentrated loads, soft ground and drainage changes need qualified site assessment.
Geotextile may serve separation or filtration in a designed system. It is not a universal weed-fabric requirement or a promise to repair unsuitable ground. Keep surface runoff, internal drainage and support requirements distinct. More gravel or more slope is not automatically the right fix.
Accessibility when the pad serves a covered facility
Do not assume gravel exempts a parking area from applicable accessibility rules. The U.S. Access Board says unpaved parking facilities still need compliant accessible spaces and access aisles. Required surfaces must be firm, stable and slip resistant; most loose gravel needs suitable treatment and continued maintenance to meet those properties.7, 8 This is a U.S. ADA planning flag, not a claim that every private residential pad has the same obligations. Determine the facility’s scope and local requirements before choosing the finish.
Quantity formula and selected-depth chart
Net cu ft = area (sq ft) × selected thickness (in) ÷ 12.
Net cu yd = area × thickness ÷ 324. Calculate base and finish separately. Identify whether the measured target is loose or finished/compacted volume before converting it into an order.
| Selected footprint | Area (sq ft) | 4-in net layer (cu yd) | 6-in net layer (cu yd) | 8-in net layer (cu yd) |
|---|---|---|---|---|
| 10 × 20 ft | 200 | 2.469 | 3.704 | 4.938 |
| 12 × 24 ft | 288 | 3.556 | 5.333 | 7.111 |
| 20 × 20 ft | 400 | 4.938 | 7.407 | 9.877 |
| 12 × 40 ft | 480 | 5.926 | 8.889 | 11.852 |
These depths are arithmetic inputs, not recommendations by vehicle type. Displayed values are rounded to three decimals. No volume conversion, density, handling reserve or supplier sales rounding is included. A geometric total does not approve pad dimensions, drainage or load capacity.
Three checked examples
1. A 12 × 24-foot layered estimate
Area = 288 sq ft. A selected 5-inch finished base contains 120 cu ft = 4.444444 finished cu yd. A selected 2-inch finished finish layer contains 48 cu ft = 1.777778 finished cu yd. Their geometric sum is 6.222222 cu yd. Do not turn that sum into a one-product order using a generic density.
2. A 10 × 20-foot layer with a defined conversion
At a selected 6-inch finished depth, net volume is 100 cu ft = 3.703704 finished cu yd. Suppose a hypothetical verified material retains 80% of its loose volume at the required installed condition. Loose target = (100 ÷ 27) ÷ 0.80 = 4.629630 cu yd. At quarter-yard sales increments, round up to 4.75 loose cu yd. Adding 20% instead would give 4.444444, a different relationship. No separate reserve is included.
3. A 12 × 40-foot layer and a weight example
At a selected 8-inch finished depth, geometry is 320 cu ft = 11.851852 finished cu yd. With a hypothetical verified factor of 1.15 loose yards per finished yard, target volume is 13.629630 loose cu yd. At half-yard sales increments, round to 14 loose cu yd. If a matching hypothetical density is 2,800 lb per loose yard, that order weighs 39,200 lb = 19.6 US short tons. Inputs are examples, not an RV design, density range or safe truck payload.
Confirm the final order
- Use a defined loose-to-finished relationship for each product. An undefined “10% extra for settling” hides the volume basis.
- Convert to weight only with a matching supplier density, moisture/volume state and ton unit. One US short ton is 2,000 lb.
- State any separately chosen reserve and actual sales increment; do not round the chart display before calculating.
- Confirm minimum delivery, taxes, fees, access and unload location. Have the carrier establish actual legal payload and route limits.
Maintenance: use the condition, not a guarantee
American Rock Supply suggests a 10-15-year interval before a fresh surface layer for a properly built pad.1 That is a supplier estimate, not a promise for this site. Inspect for rutting, displaced stone, ponding, edge erosion and support settlement. FHWA describes traffic displacing and separating aggregate.4 Diagnose recurring trouble rather than simply ordering another layer; keep any required accessible surfaces and routes working.
FAQ
Is a two-inch #57 cap always best?
No. It appears in one supplier recipe, while another promotes a fines-bearing road-base approach.1, 2 The actual layer requirements determine the finish.
Does an RV always need eleven inches?
No universal thickness is established here. Ground, loaded axle/support forces and construction requirements matter more than the vehicle label.
Is fabric mandatory?
Choose a specified separation/stabilization system when the design needs it. Generic landscape fabric does not establish ground support.
Can I skip local approval because the surface is gravel?
Do not assume that. Check municipal rules, boundaries and drainage requirements before excavation.2
Related tools and guides
Gravel calculator | Parking lot planning | CA6, CA7, #53 and #73 | Yards and US short tons converter
Sources
- American Rock Supply: Gravel Parking Pad (September 2026 supplier recipe and maintenance estimate)
- Hello Gravel: Parking Pad Road Base (supplier product and local-approval advice)
- Ozinga: CA6 Base Stone (supplier regional names and material variants)
- FHWA: Gravel Roads Construction and Maintenance Guide (road context: support, loads, drainage and displacement)
- 811: Before You Dig (utility response/waiting and safe digging)
- Andersen Hitches: Trailer Jack Blocks (manufacturer ratings vary by product and stacking configuration)
- U.S. Access Board: ADA Parking Spaces (unpaved-lot applicability and accessible surfaces)
- U.S. Access Board: ADA Floor and Ground Surfaces (loose-material treatment and maintenance caution)