How Much Gravel for a 20×20 Area?
A 20×20 area at a depth of 3 inches requires 4.25 cubic yards of aggregate (~6.38 tons compacted). This is equal to approximately 1 standard 10-yard tri-axle dump truck load.
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Material Spec & Excavation Profile
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Takeoff Schedule Summary
| Item | Quantity | Unit | Est. Cost |
|---|---|---|---|
| Compacted Volume | 4.25 | yd³ | $191 |
| ↳ Loose quarry measure | 3.7 | yd³ | (settles 15%) |
| Hauling Weight (Wet) | 6.38 | tons | ~5.95 dry |
| Tri-Axle Truckloads | 1 | trip(s) | $125 |
| Geotextile Underlayment | 460 | sq ft | $69 |
Material Takeoff & Accessory Checklist
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| Item / Specification | Category | Quantity | Unit Price | Total Est. | Supplier / Order |
|---|---|---|---|---|---|
Washed Pea Gravel (3/8") Bulk delivery, compacted depth of 3" over 400 sq ft (includes 15% compaction factor) | primary | 4.25 cu yds | $230 | Local Supplier | |
Heavy-Duty Non-Woven Geotextile Driveway Underlayment (4ft x 100ft) Separates sub-grade soil from aggregate, prevents rutting and weed growth | accessory | 1 rolls (400 sq ft) | $68 | Home Depot | |
6" Steel Landscape Staples / Anchor Pins (Box of 200) For pinning fabric to soil before aggregate placement | fastener | 1 boxes (200 pcs) | $25 | Amazon | |
Bulk Dump Truck Hauling & Delivery (1 trip) Standard local quarry/supplier drop fee (within 15-20 mile radius) | accessory | 1 trips | $85 | Local Supplier |
Calculation Mechanics: Aggregate & Tonnage
Formulas adhere to ASTM standards, ACI 318 guidelines, and standard construction estimating practice.
Step-by-Step Derivation Breakdown:
- 1Surface area: 20 ft × 20 ft = 400 square feet.
- 2Raw cubic feet: 400 sq ft × 0.250 ft = 100.00 cu ft.
- 3Divide by 27: 100.00 ÷ 27 = 3.7 loose cubic yards.
- 4Apply 15% compaction settling factor = 4.25 compacted cubic yards.
- 5Calculate tonnage based on 2800 lbs/yd³ density: (4.25 × 2800) ÷ 2,000 lbs = 6.38 tons.
- 6Dump truck trips: Tri-axle dump trucks can legally haul ~10-12 yards or 15 tons max per highway axle weight limits = 1 load(s).
Field Inspection & Trade Best Practices
- Subgrade preparation: Excavate topsoil down to solid subsoil clay/rock before placing base aggregate.
- Geotextile fabric: Never skip geotextile underlayment on driveways or heavy parking; stone will migrate downward without it.
- Lifts and tamping: Place crusher run in maximum 3-inch to 4-inch lifts and compact each lift with a vibratory roller.
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Frequently Asked Questions for 20×20 Areas
How many tons of gravel are in a cubic yard?
Crushed stone and gravel typically weigh between 2,700 and 2,950 lbs per cubic yard, which converts to approximately 1.35 to 1.48 tons per cubic yard.
Why do I need a compaction factor?
Loose gravel settles and locks together when rolled or driven on by heavy vehicles. Adding 15% to 20% ensures your finished gravel depth meets grade after compaction.
Do I need geotextile fabric under the gravel?
Yes, installing a non-woven geotextile underlayment fabric prevents crushed rock from sinking into the subsoil mud and blocks persistent weed growth.