How thick should paver base be?
At least 4 inches (100 mm) of compacted base for patios and walks and 6 inches (150 mm) for driveways, under 1 inch of sand.
The Concrete Masonry & Hardscapes Association (CMHA, which now includes the former ICPI) gives these minimums for interlocking concrete pavements over well-drained soil:[1]
| Use | Compacted base | Bedding sand |
|---|---|---|
| Patios, walks and other pedestrian areas | at least 4 in (100 mm) | 1 in (25 mm), uncompacted |
| Residential driveways | at least 6 in (150 mm) | 1 in (25 mm), uncompacted |
CMHA adds that colder climates and continually wet or weak soils need thicker bases.[1] For an unpaved gravel drive, see the driveway gravel calculator and the gravel depth guide. Oregon State's homeowner guide uses 4–6 inches of crushed rock such as ¾-minus, thicker on soft clay or where the paving will be driven on.[3]
Why order more base than the finished depth
Order about 17% more base than the compacted volume.
Base aggregate is delivered loose. The US Army's earthmoving tables give a loose-to-compacted factor of 0.86 for sand or gravel, which means about 1.17 loose cubic yards for every compacted cubic yard.[4] That 17% is the calculator's default compaction allowance. Penn State's dense-graded road aggregate compacts more under a heavy roller: 8 inches loose becomes about 6 inches.[5] Raise the allowance if your supplier or your own test says so.
CMHA calls for the base to be spread and compacted in lifts of 4–6 inches (100–150 mm) with a plate compactor, to at least 98% standard Proctor density.[1] Oregon State's guide compacts it in three thinner layers and notes that slightly moist base compacts more easily.[3]
What goes in each layer
- Base: dense-graded aggregate, with particles from 1½ in or ¾ in down to fines.[2] Bagged paver base is sold in 0.5 cu ft bags by at least one major manufacturer.[7]
- Bedding sand: a nominal 1 inch of sand meeting ASTM C33, screeded and not compacted until the pavers are compacted on top.[1]
- Permeable pavers: the bedding layer is about 2 inches of No. 8 stone instead of sand.[2] Use the gravel setting for that layer.
- More on sand weights, bulking and bag sizes is on the sand calculator page.
Worked example: 12 × 16 ft patio
A 12 × 16 ft patio needs about 2.8 loose cubic yards of base and 0.6 cubic yards of bedding sand.
| Layer | Finished depth | Volume to order | Approx. weight |
|---|---|---|---|
| Bedding sand | 1 in | 16 cu ft (0.59 yd³) | 0.77–0.86 tons |
| Base aggregate | 4 in compacted | 74.9 cu ft loose (2.77 yd³) | 3.5–4.5 tons |
Base weights vary (see how much a cubic yard weighs): a New Mexico state table gives base course as 1.25 tons per cubic yard,[6] and Penn State's ordering figure for its road aggregate is about 1.62 tons per loose cubic yard.[5] In 0.5 cu ft bags this patio would take 150 bags of base and 32 bags of sand. That is a lot to carry; at this size, compare the price of a bulk delivery.
How deep to dig
Dig to the base depth plus 1 inch of sand plus the paver thickness: about 7⅜ inches for 60 mm pavers on a 4 inch base.
excavation depth = compacted base + 1 in sand + paver thickness
For a 2⅜ in (60 mm) paver on a 4 in base, dig about 7⅜ inches. Oregon State also marks the outline about 8 inches outside the paved area,[3] so the base extends past the edge; add that margin to your measurements before calculating.
Pavers are a separate orderFor the pavers themselves, Oregon State's guide adds 5% for cuts, or 10% if the pattern has many cuts.[3] To count brick pavers, use the custom size option in the brick calculator with a joint of 0.
Frequently asked questions
How much paver base do I need?
Area × compacted depth, plus about 17% for compaction.[4] A 12 × 16 ft patio with 4 inches of base needs about 2.77 cubic yards of loose base.
How thick should paver base be for a patio?
At least 4 inches (100 mm) compacted over well-drained soil, and at least 6 inches (150 mm) for residential driveways.[1]
How much sand goes under pavers?
A nominal 1 inch (25 mm), screeded and left uncompacted until the pavers go down.[1]
How many bags of paver base per square foot?
At 4 inches compacted with 17% extra, each square foot takes about 0.39 cu ft of loose base, or 0.78 bags of 0.5 cu ft.
Sources
- Construction of Interlocking Concrete Pavements (PAV-TEC-002-22)
- Glossary of Terms for Segmental Concrete Pavement (PAV-TEC-001-23)
- 10-Step Guide to Installing Pavers
- FM 5-434 Earthmoving Operations, Tables 1-1 and 1-2 (material weights, swell and conversion factors)
- Driving Surface Aggregate (DSA) Handbook
- Conversion Factors for Construction Materials and Common Minerals (from BLM Handbook H-3890-1)
- Hardscapes product line