Almost every failed paver patio failed underneath. The pavers themselves are close to indestructible; what sinks, tilts and opens up joints is the layer nobody sees. And the single most common cause is a base that was built to whatever depth the homeowner ran out of patience at, rather than to a depth the soil and climate actually require.
The standard answer is 4 inches of compacted crusher run under a 1-inch sand setting bed. That number is correct, but it is a minimum for light foot traffic on decent draining soil. Treat it as the floor of the range, not the recommendation, and then add depth for clay, for frost, and for anything heavier than people walking.
Buying tip: Ask the yard for crusher run, road base or dense-graded aggregate — a mix of angular stone and fines that locks up hard. Clean washed stone with no fines will never compact into a rigid base for a sand-set patio, no matter how thick you make it.
Base Depth by Use and Soil
Base thickness is a function of two things: how much load the surface carries, and how poorly the soil beneath drains. Sandy or gravelly subgrade sheds water and supports load well, so you can stay near the minimum. Clay holds water, swells, softens and heaves, so it needs more stone above it to spread the load and more drainage capacity to keep water moving.
| Situation | Compacted base | Total excavation |
|---|---|---|
| Foot-traffic patio, sandy soil | 4 in | 7–8 in |
| Foot-traffic patio, clay soil | 6 in | 9–10 in |
| Patio in a hard-freeze climate | 8–10 in | 11–13 in |
| Walkway or garden path | 4 in | 7 in |
| Driveway or parking pad | 8–12 in | 11–15 in |
| Hot tub or heavy structure | Engineered slab | Consult local code |
Total excavation is base depth plus 1 inch of sand plus the thickness of your paver, which is usually 2 3/8 inches for standard concrete units and 2 3/4 to 3 inches for thicker ones. Measure your actual paver before you dig; a half-inch error across a whole patio is a lot of wasted material and a finished height that no longer meets the door threshold.
Why 4 Inches Is the Floor
A compacted aggregate base does one job: it spreads a concentrated point load out over a wider area of subgrade so the soil never sees pressure it cannot carry. That load spreads outward at roughly a 45-degree cone. Under 4 inches of base, a footstep on one paver is distributed across several times its footprint by the time it reaches soil. Under 2 inches, it barely spreads at all, and the soil deflects.
There is a practical reason too. A plate compactor densifies aggregate in lifts of about 3 to 4 inches. Below roughly 4 inches total you cannot get a uniform, fully compacted layer — you get a thin skin of dense stone over loose material, which settles unevenly during the first year. Depth is what makes proper compaction physically possible.
Whatever depth you choose, build it in lifts. Spread 3 to 4 inches, compact it in two directions, then spread and compact the next. Compacting 8 inches in one pass leaves the bottom half loose, which is functionally the same as never having installed it. Our paver base preparation guide walks through the full sequence.
Frost Depth Changes the Math
Frost heave is not caused by cold. It is caused by water in fine-grained soil freezing, expanding and lifting whatever sits on top — then dropping it back somewhere slightly different in spring. Do that for five winters and a patio that started flat is a wave. The defence is not to dig below the frost line, which for a patio would be absurd, but to remove the water and the frost-susceptible fines from the layer that matters.
In climates with a frost depth of 30 inches or more, go to 8 to 10 inches of base and consider an open-graded system instead of a sand-set one: clean angular stone all the way up, chips instead of sand for the bedding layer, and permeable joint material. Water drains straight through and never sits where it can freeze. It is the standard build in Canada and the northern US for a reason.
Whichever system you use, the surface must still shed water. Slope the finished patio 1 inch per 8 feet away from the house, and pitch the compacted base to the same grade before you screed sand — base slope, not sand thickness, is what creates drainage. Getting that wrong is the leading cause of standing water on a patio.
The Excavation Math
Once you know your depth, the volume calculation is straightforward. Work in feet: length times width times depth-in-inches divided by 12, then divided by 27 to get cubic yards. Crusher run weighs about 1.55 US tons per cubic yard, so multiply your yards by 1.55 if the yard sells by weight.
- Measure the finished patio. A 12 by 16 foot patio is 192 square feet. Add 6 inches of base beyond each edge for the perimeter shelf that supports the edge restraint.
- Pick your compacted depth. Say 6 inches for clay soil. That is 192 × 0.5 ft = 96 cubic feet, or 3.6 cubic yards.
- Add a compaction allowance. Dense-graded aggregate loses roughly 20 to 25 percent of loose volume when compacted, so order about 4.5 cubic yards — near 7 tons.
- Add the sand bed. 1 inch over 192 square feet is 16 cubic feet, or 0.6 cubic yards. Do not round this one up and spread it thicker.
- Dig to total depth. 6 in base + 1 in sand + 2 3/8 in paver = 9 3/8 inches below finished grade.
Rather than doing this by hand, put your dimensions into the paver base calculator, which handles the compaction allowance, and the paver sand calculator for the bedding layer. If you are buying dense-graded aggregate by the ton, the crusher run calculator converts volume to tonnage directly.
The One Inch of Sand Rule
The sand bedding layer is exactly 1 inch, screeded flat and never compacted before the pavers go down. Homeowners routinely use 2 or 3 inches because it makes leveling easier — and it does, for about a month. Thick sand is not a structural layer; it migrates, washes and rutts under load, and the pavers ride it down into dips that no amount of re-sanding will fix.
If your base is uneven, the fix is more base and another pass with the compactor, not more sand. Use coarse concrete sand, not mason sand or play sand. And do not confuse the bedding sand with the joint filler: joints get polymeric sand, which covers 50 to 75 square feet per 50-pound bag depending on joint width.
Bottom Line
Use 4 inches of compacted crusher run as an absolute minimum on well-drained soil, 6 inches on clay, and 8 to 10 inches where the ground freezes hard. Add 1 inch of concrete sand, never more. Compact in 3 to 4 inch lifts, slope the base itself at 1 inch per 8 feet, and extend the base 6 inches past the paver edge.
Base stone is the cheapest material on the job and the only one you cannot add later without tearing everything out. Two extra inches of crusher run on a 200 square foot patio costs well under $100 and is the best money you will spend on the entire project.
