How high-performance turf drainage works

Drainage hinges on void space, interlock, and controlled slope. Clean, angular aggregate creates large, connected voids that move water quickly while staying stable under load. A non-woven geotextile keeps soil fines from migrating up into the base so those voids stay open. A steady 1 to 2 percent surface slope tells water where to go.

Void space drives flow

Washed, angular stone has high permeability because there are no binding fines to clog pathways. Angular faces lock under compaction so the base stays tight without crushing the voids that handle runoff and rinses.

Separation fabric protects the base

Install a non-woven geotextile over prepared subgrade. It stops soil pumping, improves load distribution, and extends system life in wet cycles.

Slope controls direction

Shape the subgrade and finished base to 1 to 2 percent slope away from structures and toward approved discharge points. Even on permeable builds, slope prevents nuisance ponding after extreme events.

Recommended base specification

Materials

  • Primary base: washed, angular open-graded stone conforming to ASTM No. 57 or No. 89.
  • Optional top dressing for smoothness: a thin layer of smaller open-graded chip rock such as No. 8 or No. 9, not fines.
  • Separation layer: non-woven geotextile, 4 to 8 oz per square yard, puncture resistant.
  • Edge restraint: composite bender board, concrete curb, or paver edge secured to subgrade or base.

Depth by application

  • Residential lawns and play areas: 3 to 4 inches of open-graded stone.
  • Pets, high-traffic patios, or heavy rainfall zones: 4 to 5 inches.
  • Driveways, carts, or sports: 5 to 6 inches, plus underdrains as needed.

Compaction and tolerances

  • Place stone in 2 inch lifts and compact with a vibratory plate or roller until stable and unyielding under foot traffic, while maintaining permeability.
  • Target flatness within 3/8 inch over 10 feet. Confirm final slope with a level or laser.
  • Do not add stone dust or soil fines to tighten the surface. Preserve the clean matrix for fast flow.

Soil and site adjustments

Clay or poorly draining subgrades

Increase base depth and add a perforated underdrain wrapped in fabric, set at the low point and tied to daylight or a dry well. This creates a pressure relief path during long storms.

Freeze-thaw climates

Use clean open-graded stone with geotextile to minimize frost heave. Slightly increase base depth and keep surface grades true so meltwater moves off quickly.

Rooftops, balconies, and concrete slabs

Use a drainage tile or panel over the hard surface, maintain at least 1 percent slope to scuppers or drains, and include perimeter relief gaps. On-grade open-graded stone is not used over concrete.

Alternatives compared

  • Decomposed granite or stone dust: smooth to screed but slower drainage and higher clog risk from fines. Prefer clean stone for wet or pet-heavy installs.
  • Pea gravel: rounds do not interlock, can shift, and trap waste. Choose angular stone for stability and flow.
  • Dense graded road base or recycled concrete with fines: compacts hard but loses permeability as fines migrate. Not ideal when rapid drainage matters.
  • Drainage mats or panels: valuable on rooftops and slabs, and as a supplement over heavy clay with underdrains.

Step-by-step install checklist

  1. Call to locate utilities. Mark edges and drainage exits.
  2. Excavate turf area to allow base depth plus turf thickness. Remove organics and soft spots.
  3. Shape subgrade to 1 to 2 percent slope and proof-roll. Pre-wet if dusty.
  4. Place non-woven geotextile over subgrade and upturn at edges.
  5. Install edge restraints secured to subgrade or base.
  6. Place open-graded stone in 2 inch lifts, compact each lift, and maintain slope.
  7. Optionally screed a thin layer of smaller clean chip rock for a smooth, even surface.
  8. Lay turf, align grain, and seam per manufacturer guidance. Secure edges.
  9. Add recommended infill, brush to stand fibers, rinse, and verify drainage.

Copy-ready spec

  • Base: washed open-graded angular stone, ASTM No. 57 or No. 89, depth 3 to 6 inches per plan.
  • Geotextile: non-woven, 4 to 8 oz per square yard beneath base and around any underdrain.
  • Slope: 1 to 2 percent away from structures to approved discharge.
  • Compaction: vibratory compacted in lifts to a stable, non-yielding surface without adding fines.
  • Tolerances: surface within 3/8 inch in 10 feet. No standing water after rinsing.

Maintenance for peak drainage

  • Keep the surface clean by blowing leaves and brushing fibers upright.
  • For pet areas, rinse regularly and use enzyme cleaners as needed.
  • Do not top-dress with decomposed granite or soil. If settlement occurs, lift turf and add clean stone.