Patio base: the short answer
For a pedestrian patio under ideal conditions, CMHA identifies 4 inches (100 mm) of aggregate base as a minimum starting point. The same source defines ideal conditions narrowly: a strong, structurally sound, well-draining subgrade in a stable climate. Weak soil, drainage problems and freezing can require a thicker or different section.
Do not turn a minimum into a universal recipe.
A patio may carry foot traffic instead of vehicles, but it can still settle when placed over disturbed fill, wet clay or poorly prepared subgrade.
Keep four layers visible
| Layer | Planning role | Decision owner |
|---|---|---|
| Paver | Finished surface and thickness | Selected product |
| Bedding course | Uniform setting layer | Paver system/specification |
| Aggregate base | Load distribution and stable platform | Site design/specification |
| Soil subgrade | Foundation below all imported material | Actual site condition |
The excavation calculator adds the paver, bedding and base thicknesses. The main material calculator sizes gravel and sand separately so their densities and allowances do not get mixed.
Five patio checks before choosing depth
1. Was the soil recently disturbed?
Backfilled utility trenches, new construction and recently graded areas can behave differently from long-undisturbed soil. A calculator cannot identify hidden fill.
2. Where does water leave?
Confirm the intended surface grade, the path away from buildings and whether the base could trap water. Permeable and conventional paver systems use different layer assemblies.
3. Does the ground freeze?
Freeze-thaw exposure changes the design problem. Local experience, manufacturer requirements and professional advice should override a generic minimum.
4. What loads will reach the patio?
Foot traffic, grills and furniture differ from vehicle traffic, hot tubs, masonry kitchens or retaining structures. Heavy point loads need specific review.
5. What does the selected paver system require?
Use its bedding material, thickness, edge restraint and joint instructions. Do not combine guidance from incompatible systems.
12 × 16 ft patio example
A 192 sq ft rectangle with a 4 in compacted base, 1 in bedding course, 2.375 in paver, 15% base order allowance and 5% waste produces this preliminary takeoff with the site defaults:
- Base gravel: about 2.86 yd³ or 4.29 US short tons at 1.50 ton/yd³
- Bedding sand: about 0.62 yd³ or 0.84 short tons at 1.35 ton/yd³
- Arithmetic layer stack: 7.375 in before any extra site correction
These numbers are a reproducible example, not a supplier promise. Enter the actual product density, selling unit and planned section.
Patio planning sequence
- Measure the finished patio and any base extension beyond the edge.
- Confirm finish elevation, drainage direction and transitions to doors or walks.
- Select a base and bedding assembly that matches the site and paver system.
- Use the calculators for excavation, gravel and sand arithmetic.
- Ask the supplier to confirm density, package yield, minimum order and delivery access.
- Have a qualified installer or designer review uncertain soil, drainage, frost or heavy-load conditions.
References
- CMHA — Proper Concrete Paver Base and Depth
- CMHA PAV-TEC-002 — Construction of Interlocking Concrete Pavements
- QUIKRETE Patio Paver Sands data sheet
Scope
This is preliminary planning information, not a site inspection, structural design, drainage plan, permit review or warranty.