What determines the right base thickness
Base depth is sized to handle water, weight, and movement. The goal is fast drainage and a stable, smooth platform that will not rut or wave.
- Soil type: Clay holds water and swells. Sand drains well. Poor soils need more depth and a geotextile separator.
- Rain and freeze cycles: More rain or freeze thaw needs more stone and better drainage paths.
- Use and traffic: Dogs, kids, sports, and carts load the surface. Heavier use needs more base.
- Slope and edges: Proper grade and solid edging lock the system in place.
Recommended base depths by use
Residential lawns and landscapes
Typical yards perform well with about 3 to 4 inches of compacted, well graded angular stone. This balances stability and drainage without overbuilding.
Pets and high foot traffic
Step up to roughly 4 to 6 inches, especially with active dogs or tight turns near gates. More depth reduces odor risk by moving water through faster.
Play areas and multi use spaces
Target 4 to 6 inches for playgrounds or training zones. If safety fall height is required, add an impact pad beneath the turf per the tested system.
Putting greens
Install about 4 inches of compacted base rock, then shape with 1 to 2 inches of finer aggregate for smooth contours. Compact each lift before shaping.
Over concrete or asphalt
No thick stone base is needed on solid slabs. Use a drainage tile or a 0.5 to 1 inch leveling layer to manage water and smooth irregularities.
Best base materials
- Angular crushed stone that compacts and interlocks. Common choices include 3/4 inch minus or 3/8 inch minus road base.
- A thin top layer of finer aggregate can help final grading for a tight, smooth finish.
- A non woven geotextile underlayment over clay or soft subgrade separates soil from stone and improves longevity.
Avoid rounded pea gravel as the primary base. It shifts under load and compacts poorly.
Drainage and slope
- Grade the subgrade at 1 to 2 percent away from structures.
- Keep the finished base flat and true while maintaining that overall flow.
- In wet zones or low pockets, add a trench drain or French drain tied to daylight or a proper outlet.
Regional adjustments
- Clay or high rainfall: Use closer to 5 to 6 inches, add geotextile, and consider a subdrain in known wet areas.
- Well draining sandy soils or arid climates: About 3 to 4 inches usually performs well.
- Freeze thaw regions: Use well graded angular stone and compact in thin lifts. Keep water moving with correct slope.
How to build a stable base
- Call 811 to locate utilities before digging.
- Excavate organic material to the required depth so finished turf matches desired grade.
- Correct the subgrade slope and proof roll to find soft spots. Stabilize any weak areas.
- Install geotextile if soils are clay, silty, or mixed.
- Place base stone in 2 inch lifts. Lightly moisten and compact each lift to 90 to 95 percent with a plate compactor.
- Fine grade with a thinner top layer for a smooth, even plane.
- Install edging that holds vertically and horizontally. Then place turf, seam, and infill per spec.
Common mistakes to avoid
- Too little base depth in clay or wet zones.
- Poor compaction or compacting only the top.
- Using rounded gravel that never locks.
- No geotextile over soft or expansive soils.
- Flat grade near structures that traps water.
Quick material calculator
- Depth in feet = base inches ÷ 12
- Cubic yards = area (sq ft) × depth (ft) ÷ 27
- Tons of stone ? cubic yards × 1.4 to 1.6
Example: 500 sq ft at 4 inches. Depth = 0.333 ft. Volume ? 500 × 0.333 ÷ 27 = 6.2 cubic yards. At 1.5 tons per cubic yard, order about 9.3 tons.
When to add drainage tile or pads
- Over concrete, balconies, or roof decks, use drainage tiles to create airflow and rapid evacuation.
- For safety surfacing or sports, use a rated pad per the system specification.
Want a spec built for your site
Send your square footage, soil type, and use case. We will give you a clear base depth, material spec, and install steps that perform in your climate.
