Quick answer
For a typical paver patio, dig out enough for about 4 to 6 inches of compacted crushed-stone base, 1 inch of bedding sand and the paver thickness. With standard 2 3/8 inch pavers and a 4 inch base, that is a dig of about 7 1/2 to 8 inches. Compact the base in lifts of 2 to 4 inches, slope it about 1/8 to 1/4 inch per foot away from the house, then screed 1 inch of sand on top.
Base depth by project
| Project | Compacted base | Bedding sand |
|---|---|---|
| Walkway, firm well-drained soil | 4 in | 1 in |
| Patio, average soil | 4 to 6 in | 1 in |
| Patio on clay or wet soil, or in frost areas | 6 to 8 in or more | 1 in |
| Driveway | 8 to 12 in | 1 in |
The base works by spreading load over the soil and draining water away. Soft clay, poor drainage and deep frost all call for the thicker end. When in doubt, add 2 inches; base stone is far cheaper than a rebuild.
Materials
- Base: crushed stone with fines, usually sold as 3/4 inch minus, crusher run, dense grade aggregate or "paver base." The mix of sizes and dust locks together when compacted. Rounded pea gravel does not lock and should not be used.
- Bedding sand: coarse washed concrete sand. Industry guidance generally advises against stone dust and fine mason sand for the bedding layer because they hold water and do not drain well.
- Geotextile fabric: optional over clay or soft soil. It keeps base stone from pushing down into the soil over time.
- Edge restraint: plastic, aluminum or concrete edging that holds the outer pavers in place.
The paver base calculator gives cubic yards and tons of base plus the bedding sand for your patio size.
Step by step
- Call 811 at least a few days before digging so buried utility lines are marked. It is free.
- Lay out the patio. Mark the outline with paint or stakes and string. Extend the excavation about 6 to 12 inches past the paver edge on all sides so the base supports the edge restraint.
- Set the slope. Run a string line from the high side (by the house) to the low side and lower it about 1/8 to 1/4 inch for every foot of run. A 12 ft patio drops roughly 1 1/2 to 3 inches. Measure down from this string to set dig depth.
- Excavate. Remove sod, roots and topsoil to the planned depth. Keep the bottom roughly parallel to your finished slope. Remove any soft pockets and replace them with base stone.
- Compact the subgrade. Run a plate compactor over the bare soil. If footprints stay deep or the soil pumps up water, dig deeper or add fabric.
- Lay fabric if you are using it, overlapping seams by about 12 inches.
- Add base in lifts. Spread 2 to 4 inches of base stone, lightly dampen it, and make two or more passes with the compactor. Repeat until you reach full depth. Thick single layers never compact fully in the middle.
- Check the surface. The top of the base should match your slope and be flat within about 3/8 inch under a 10 ft straightedge. Fix low spots with base stone, not sand.
- Install edge restraint on the compacted base, or wait until the first rows of pavers are laid, depending on the edging system.
- Screed the sand. Lay two 1 inch pipes on the base as rails, fill between them with sand and pull a straight board across. Remove the pipes and fill the grooves. Do not walk on screeded sand or compact it before laying pavers.
How much material for a 12 x 12 ft patio
Area is 144 sq ft. Add 6 inches on each side for the base overhang: 13 x 13 = 169 sq ft. A 4 inch compacted base is 169 x 4 / 12 = about 56 cu ft, or 2.1 cubic yards. Crushed base stone weighs about 1.4 to 1.5 tons per cubic yard loose, so plan on roughly 3 tons, and order 10 to 15 percent extra because it compacts. Bedding sand at 1 inch over 144 sq ft is 12 cu ft, about 0.44 cubic yards or 24 half-cubic-foot bags.
Tools you will need
- Plate compactor (rental is usually by the half day or day)
- Square shovel, wheelbarrow and hard rake
- String line, line level, stakes and a 4 ft level
- Two 1 inch screed pipes and a straight 2x4
- Tape measure and marking paint
Mistakes to avoid
- Using sand to level the base. Sand thicker than about 1 inch shifts and leaves dips. Fix the base itself.
- Skipping the slope. A dead-flat patio puddles and can send water toward the foundation.
- Compacting dry stone. Base compacts best slightly damp, not soaked.
- Cutting the overhang. Without base past the edge, outer pavers sink and spread.
Building a low wall or seat around the patio? The retaining wall block calculator counts blocks and base for it.