Driveway base: the short answer
For a residential driveway under ideal conditions, CMHA identifies 6 inches (150 mm) of aggregate base as a minimum starting point. Parking areas and residential streets move to an 8 in ideal-condition minimum, while streets and heavy-duty pavements require professional design. Weak soil, repeated heavy vehicles, drainage problems and freezing can require more.
Vehicle traffic changes the failure mode.
Wheel paths repeatedly load the same zones. Settlement, rutting and edge movement can appear even when the arithmetic quantity is correct but the pavement section or compaction is not.
Define the actual load
- Passenger cars only, or pickups, vans, trailers and delivery trucks?
- Occasional crossing, daily parking or repeated turning and braking?
- Any RV, service vehicle, dumpster or construction access?
- Will loads travel close to an unsupported edge?
- Does the paver thickness and pattern suit the intended traffic?
When the maximum load is uncertain, do not pick a preset from the average vehicle. Review the heaviest credible use.
Driveway layer decisions
| Decision | Why it matters | Calculator treatment |
|---|---|---|
| Subgrade preparation | Supports the full system | Not designed |
| Base material and thickness | Distributes vehicle loads | Quantity only |
| Bedding course | Supports and aligns pavers | Separate quantity |
| Paver product/thickness | Carries surface stress | Excavation thickness only |
| Edge restraint | Resists lateral movement | Not calculated |
Compaction is a field requirement, not just 15%
The calculator’s default 15% is a loose-order planning allowance. It is not a proof of achieved field density. CMHA’s application guidance states that aggregate base under pedestrian and residential driveway pavements should reach at least 98% of standard Proctor density under the referenced specification. Project specifications, test methods and equipment determine how that is verified.
Read the dedicated paver base compaction guide before using the order allowance as if it were an installation instruction.
20 × 40 ft planning example
An 800 sq ft driveway with a 6 in compacted base, 1 in bedding course, 3.125 in pavers, 15% base order allowance and 5% waste produces a large material and excavation task:
- Base order volume: about 17.89 yd³ before replacing the default density
- At 1.50 short ton/yd³: about 26.83 short tons
- Bedding sand: about 2.59 yd³ at a 1 in layer with 5% waste
- Uniform excavation stack: 10.125 in before any site correction
Large quantities amplify small assumption errors. Confirm the base width, finished grades, supplied density, truck capacity and minimum loads.
Stop and get project-specific help when
- The driveway carries commercial, emergency, RV or repeated heavy-truck traffic.
- Subgrade contains organic soil, soft clay, uncontrolled fill or wet zones.
- Water has no clear outlet or a permeable system is being considered.
- The project is in a severe freeze-thaw climate.
- Retaining walls, slopes, utilities, garage thresholds or public right-of-way work affect the section.
- Local permit, code or manufacturer documents require a different design.
References
- CMHA — Proper Concrete Paver Base and Depth
- CMHA PAV-TEC-010 — Application Guide for Interlocking Concrete Pavements
- Unilock — How to Build a Paver Driveway
Scope
This guide supports preliminary material planning. It does not replace pavement design, geotechnical review, drainage design, code review or installer responsibility.