Paver patio base: how deep to dig and what to order
Most paver patios that sink, shift or grow weeds fail because of the base, not the pavers. Here's how to size each layer and how much to dig.
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The layers of a paver patio
| Layer (top to bottom) | Typical thickness | Material |
|---|---|---|
| Pavers | 2⅜ in (60 mm) is standard for patios | Concrete pavers, brick or stone |
| Bedding sand | About 1 in, screeded flat | Coarse, washed concrete sand |
| Base | 4–6 in compacted (more on clay or in cold climates) | Crushed stone or road base with fines, or clean open-graded stone |
| Subgrade | — | Native soil, stripped of topsoil and compacted |
The Interlocking Concrete Pavement Institute's guidance for pedestrian areas like patios and walkways is a compacted aggregate base of about 4 to 6 inches under roughly an inch of bedding sand; driveways need substantially more base.
How deep to dig
Example: standard 2⅜ in pavers on a 4 in base
- 2⅜ + 1 + 4 = about 7⅜ in below the finished patio surface
- With a 6 in base: about 9⅜ in
Measure from where you want the finished surface to be — typically flush with the lawn at the edges and at least an inch or so below any door threshold.
Extend the base past the edges
The edge restraint needs solid ground to be spiked into, and the edge pavers carry loads from feet and furniture right at the border. Dig and build the base 6 to 12 inches wider than the patio on every side that isn't against a wall. Include that extra width when you calculate the base with the gravel calculator — or let the 10% allowance in the paver calculator cover it on small patios.
Slope for drainage
A patio must shed water away from the house. A common target is a fall of about ⅛ to ¼ inch per foot (1–2%). Build the slope into the subgrade and base — not the sand — so every layer is an even thickness.
Example: a patio extending 12 ft from the house
- At ¼ in per foot: 12 × ¼ = 3 in lower at the far edge
- At ⅛ in per foot: 1½ in lower
Compacting the base
- Compact in lifts of about 2 to 4 inches with a plate compactor; a single thick layer only compacts on top.
- Moisten dense-graded base slightly so the fines bind; it compacts poorly when bone dry or soaking wet.
- Check flatness with a long straightedge and string lines before spreading sand. Fix low spots with base material, not extra sand.
What to order for a 12 × 16 ft patio
| Material | Quantity (incl. extra) |
|---|---|
| 6 × 9 in pavers | about 564 (192 sq ft + 10%) |
| Base, 4 in (+10%) | about 2.6 yd³ — roughly 3.9 tons of road base |
| Bedding sand, 1 in (+10%) | about 0.65 yd³ — or 36 bags of 50 lb |
| Edge restraint | 40 ft if one 16 ft side is against the house |
Frequently asked questions
Can I use sand instead of gravel as the base?
No — sand alone shifts and washes out. Sand is only the thin bedding layer; the load-bearing base is compacted crushed stone.
Do I need landscape fabric under the base?
On clay or wet soils, a geotextile between the soil and the base keeps them from mixing and is often recommended. Weeds in the joints come from seeds blown in on top, which polymeric joint sand helps prevent.
How long does the base take?
Longer than laying the pavers. Excavation and compaction are most of the work — budget your time accordingly and consider renting a small excavator for large patios.
Sources
- Interlocking Concrete Pavement Institute (ICPI) — base and bedding layer guidance.