Paver Patio Base Depth: How Much Gravel and Sand You Actually Need

#tutorial #diymath

Every paver patio that rocks, sinks or grows weeds between the joints has the same root cause: a base that was too thin or poorly compacted. The pavers you see are the easy part. The gravel and sand underneath do the real work, so it pays to get the quantities right before the delivery truck shows up.

How deep should the base be?

Patios and walkways (foot traffic): 4 to 6 inches of compacted crushed-stone base.
Driveways (vehicle traffic): 8 to 12 inches of compacted base.
Bedding layer: about 1 inch of coarse concrete sand screeded on top of the base.

Go toward the deeper end if you have clay soil, poor drainage or a freeze-thaw climate. Crushed stone with fines (often sold as 3/4-inch minus, road base or paver base) locks together far better than round pea gravel.

Don't forget compaction

Loose gravel shrinks when you run a plate compactor over it. Plan on ordering 10 to 15 percent more than the compacted volume you calculate. Compact in 2-inch lifts so the whole depth gets dense, not just the top.

The formula

area (sq ft)  = length x width
volume (cu ft) = area x depth (in) / 12
cubic yards    = cubic feet / 27

Worked example: 12 x 16 ft patio

Gravel base (6 inches):

Area: 12 x 16 = 192 sq ft
Volume: 192 x 0.5 ft = 96 cu ft
Cubic yards: 96 / 27 = about 3.6 cu yd compacted
With a 15% allowance: about 4.1 cu yd to order

Bedding sand (1 inch):

192 x (1/12) = 16 cu ft
16 / 27 = about 0.6 cu yd

Most suppliers sell by the ton, and crushed stone runs roughly 1.4 to 1.5 tons per cubic yard, so this patio needs close to 6 tons of base.

Quick JavaScript check

const yards = (l, w, depthIn, allowance = 0.15) =>
  +((l * w * (depthIn / 12)) / 27 * (1 + allowance)).toFixed(2);

console.log(yards(12, 16, 6)); // 4.09 (base)
console.log(yards(12, 16, 1, 0)); // 0.59 (sand)

Skip the arithmetic

If you would rather plug in dimensions and get base and sand quantities in one step, the free paver base calculator on CalcQuarry handles depth, compaction and both layers. For converting cubic yards into tons for your supplier, use the gravel tonnage tool.

Final tips

Excavate 6 to 12 inches beyond the patio edges so edge restraints sit on base.
Slope the base about 1/8 inch per foot away from the house.
Lay geotextile fabric over soft soil before adding stone.

Get the base right and the pavers on top will stay flat for decades.

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