What actually determines base depth
Base depth is not one size fits all. The right build depends on how the area will be used, the soil you have, and how well the site drains. Get these factors right and your turf stays flat, fast draining, and long lasting.
- Use and load: Light foot traffic needs less than areas with frequent gatherings, play equipment, or workout rigs.
- Soil type: Clay and expansive soils need a thicker, more stable base than free draining sandy soils.
- Drainage: If water lingers after rain, plan on more depth or a drain system.
- Climate: Freeze thaw zones benefit from extra thickness and free draining aggregate to limit movement.
- Surface finish: Putting greens and bocce need a smoother, tighter base than general landscape turf.
Recommended base depth by scenario
- Most residential lawns and play areas: Plan in the 2 to 6 inch range of compacted aggregate, adjusted by soil and drainage.
- High traffic zones, dog runs, or equipment areas: Target the higher end of that range or add 1 to 2 inches for stability.
- Sports and training surfaces: Often 6 to 8 inches or more for consistent impact and planarity.
- Rooftops and balconies: Use modular drainage tiles or a thin aggregate layer paired with a pad when structural limits apply. Follow engineer guidance.
- Poor or expansive soils: Add 1 to 2 inches beyond your baseline and use a geotextile separator.
Materials that actually work
- Primary base: Angular, well graded crushed stone such as Class II road base or 3/4 inch minus. Angular particles lock and compact tight.
- Leveling course: A thin layer of fine crushed stone or decomposed granite to true the surface before turf goes down.
- Geotextile separator: Place over native soil to prevent fines migrating up and base sinking over time.
- Avoid rounded rock: Pea gravel and river rock do not interlock well and can shift.
Build sequence that holds up
- Excavate: Remove organics and dig to the planned base thickness plus turf and infill height. Call 811 before you dig.
- Rough grade: Shape the subgrade so water moves away from structures.
- Install geotextile: Lay fabric flat with overlaps per manufacturer guidance.
- Place base in lifts: Spread aggregate in thin lifts, typically about 2 inches at a time.
- Compact each lift: Use a plate compactor. Aim for firm, non yielding ground, equivalent to roughly 90 to 95 percent Proctor density.
- Fine grade: Add a thin leveling course, screed flat, and compact again.
- Edge restraint: Install bender board, concrete mow curb, or steel edging so the base and turf cannot creep.
- Proof test: Walk the area. If your heel leaves dents, compact again.
Drainage and slope
Keep water moving. Grade away from structures, tie low spots into drains where needed, and ensure the base surface sheds water evenly. In flat yards or heavy clay, add perforated drain lines or a strip drain routed to daylight or a sump.
Cold climates and expansive soils
- Freeze thaw: Favor free draining aggregate and increase thickness. Avoid trapping water beneath the base.
- Expansive clay: Use a geotextile and consider a thicker, open graded aggregate layer to reduce movement.
Quick material calculator
- Area: Length × width in feet.
- Volume: Area × planned base thickness (inches) ÷ 12 = cubic feet.
- Cubic yards: Cubic feet ÷ 27.
- Tonnage estimate: Cubic yards × 1.4 to 1.6 tons per cubic yard, depending on the aggregate.
Order a bit extra for waste and final truing rather than coming up short.
When to go beyond typical
- Vehicles or heavy loads: Treat like a light duty paving base and increase thickness accordingly.
- Precision surfaces: Putting greens and courts demand a tighter tolerance. Spend more time on fine grading and compaction.
- Chronic drainage issues: Combine a thicker base with drains and consider an open graded layer beneath the top course.
Get it done right
If you want a second set of eyes on soil, drainage, or depth choices, a certified FusionTurf pro can validate your plan and build a base that stays solid.
