How the drainage system works, layer by layer
Turf backing and perforations
Modern turf backings are engineered with perforations so surface water passes through the face and backing into the base below. The backing is rarely the bottleneck. Drain time is controlled by the base, subgrade, and outlets.
Infill’s role
Infill keeps fibers upright and helps distribute water to the perforations. It should be clean and free draining. Avoid dusty materials that can migrate and clog pores.
Free draining base
An open graded aggregate base (clean stone with voids) acts like a temporary reservoir and rapid conveyance layer. Water spreads, slows, and infiltrates into the soil or moves to a pipe or surface drain.
Edge restraints and transitions
Perimeter details must not create dams. Use beveled edges, weep gaps at curbs, or channel drains along hardscape transitions so water has a clear exit path.
Subgrade performance
The soil below the base sets your infiltration rate. Sandy or loamy soils infiltrate fast. Tight clays may need thicker base, underdrain pipe, or a planned outfall to keep the system responsive during heavy rain.
Optional underdrains
Perforated pipe in a trench or a strip drain collects water from the base for sites with slow soils, flat grades, or large catchment areas. Tie underdrains to daylight or a legal storm outlet.
Design specs that keep water moving
Slope and elevations
- Target finished surface slope of 1 to 2 percent toward an exit path.
- Hold consistent high and low points. Avoid birdbaths where grades flatten.
- Match adjacent hardscape elevations so edges do not trap water.
Aggregate selection and base depth
- Use open graded, angular, clean stone. Common choices: 3/8 inch to 3/4 inch washed aggregate with fines kept to a minimum.
- Typical landscape base depth: 3 to 6 inches. Increase depth for heavier rainfall, slow soils, or vehicle loads.
- Sports or high use areas often need 8 to 12 inches plus a stabilized layer as required by use.
Geotextile and separators
- Place a non woven geotextile over the subgrade to keep fines from migrating into the base.
- On rooftops or over concrete, use a drain mat or panel that directs water to roof drains or trench drains.
Surface water at hardscapes
- Add linear drains where turf meets concrete if slope cannot carry water away cleanly.
- Leave intentional weep gaps in curbs or edging so the base can discharge.
Cold climates and freeze thaw
- Use non frost susceptible, free draining aggregate. Keep fines low so water does not get trapped and freeze.
- Compact in thin lifts to achieve stability without choking the voids.
Pet areas
- Choose clean, well draining infills and a base that rinses easily.
- Provide a slope to a drain or soil area. Regular rinsing and enzyme cleaners keep the system fresh and flowing.
Installation steps focused on drainage
- Assess soil infiltration with a simple hose test. If water ponds, plan for thicker base or an underdrain.
- Grade subgrade to target slope. Remove soft spots and compact to a firm, uniform surface.
- Install geotextile separator where soils are fine or weak.
- Place open graded aggregate in lifts. Compact with a plate compactor. Do not add fines that seal the voids.
- True the base to final elevations. Check with a straightedge and laser for smooth, consistent slope.
- Set edging that allows drainage. Add weeps or drains at low points.
- Lay turf, seam, and infill. Brush to open the pile and confirm water flows to the planned exits.
Maintenance that preserves drainage
- Keep the surface clean. Blow off leaves and sediment before they work down into the infill.
- Power broom periodically to loosen compacted infill and restore permeability.
- Refresh or top off infill where levels drop.
- Rinse pet zones and apply enzyme cleaners as needed.
- Inspect edges and drains after storms. Clear debris so outlets stay open.
Troubleshooting puddles
- Small, isolated puddles: Lift the turf locally, re true the base, and reset. Often a quick fix.
- Widespread slow drainage: Base may be choked with fines. Vacuum extract or replace impacted sections with clean, open graded stone.
- Water trapped at edges: Add weep holes, lower a high lip, or install a channel drain.
- Slow soils: Add a perforated underdrain tied to daylight or a code compliant outlet.
Quick checklist before you build
- Defined slope and exit path
- Open graded base depth sized to rainfall and soil
- Separator fabric over fine soils
- Edges and hardscape transitions that do not dam water
- Underdrain included where soils are slow or space is flat
When to add an underdrain
Any time infiltration is poor, catchment is large, or grades are flat, a perforated pipe in a gravel trench under the base turns a good turf into a fast draining system. It is inexpensive insurance on tight clays and shaded sites.
Need a site specific drainage plan?
FusionTurf will help you size base depth, choose aggregates, and pick the right drain details for your climate. Connect with a local pro at find.fusionturf.com.
