How artificial turf drains in real conditions
Rain falls through the turf fibers and permeable backing into an open-graded aggregate base. From there, water either infiltrates into the native soil or moves to a planned outlet such as a French drain, perforated pipe, or area drain. When the system is designed correctly, artificial grass does not behave like a sealed surface.
What determines drainage performance
Permeable backing
Two common backings are perforated and fully permeable flow-through. Both allow vertical drainage when paired with a free-draining base. Lab drainage ratings for quality turf typically exceed design storm intensities, so the limiting factor is usually the base and subsoil, not the backing.
Base construction
A well-engineered base is the engine of drainage. Use open-graded, angular, washed stone that creates void space for rapid flow. Avoid dense, fine-rich mixes that hold water.
- Typical build: 3 to 5 inches of washed, angular, open-graded aggregate such as ASTM No. 57 stone.
- Optional setting layer: a thin lift of smaller clean stone for final smoothness, not compacted fines.
- Geotextile separator: placed over native soil to keep fines from migrating into the base.
- Compaction: seat the stone for stability while preserving voids. Do not over-compact into a dense, impermeable mass.
Native soil and infiltration
Subsoil controls how fast water leaves the base. Sandy or loamy soils drain quickly. Heavy clays and high water tables slow infiltration and can require underdrains or detention capacity in the base.
Grading and discharge paths
Grade finished surfaces 1 to 2 percent away from structures. Ensure there is a clear path for water to exit the area, whether by infiltration, daylighted drains, or tie-in to a managed system.
Infill and surface load
Clean, well-graded infill supports fiber and keeps flow paths open. Organic debris, silt, or compacted fines can reduce permeability. Routine cleaning maintains peak performance.
Design it right step by step
- Assess the site: identify low points, nearby hardscapes, and safe discharge locations.
- Check soils: perform a simple infiltration or percolation test to understand subsoil capacity.
- Choose backing: perforated or fully permeable, matched to site needs.
- Engineer the base: specify 3 to 5 inches of open-graded washed stone with a geotextile separator.
- Set grade: target 1 to 2 percent slope away from buildings and toward intended drainage paths.
- Plan edges: use edge restraints that do not dam water. If using curbs, include weep gaps.
- Add underdrains where needed: include perforated pipe in a trench of clean stone for slow subsoils or trapped areas.
- Select infill: clean, non-clogging infill appropriate for use and climate.
- Document and test: before infill, hose-test select areas to confirm flow through to the base and exits.
Special scenarios
Over concrete, rooftops, or decks
Use a drainage mat with channels and weep pathways. Direct flow to scuppers, area drains, or perimeter outlets. Do not block edge flow with sealed curbs.
Heavy clay or high water table
Increase base thickness, add underdrains, or include a stone detention layer to slow-release water to a safe outlet. Expect slower infiltration and design for storage.
Slopes and terraces
Anchor the turf mechanically and step the base in lifts. Include check edges or slit drains on long runs to intercept and route water.
Cold climates
Open-graded bases handle freeze-thaw well because voids relieve pressure. Ensure outlets stay clear of ice and debris.
Artificial vs natural grass for runoff
Healthy, uncompacted lawns infiltrate well, but many lawns are compacted and shed water. A permeable turf system with an open-graded base delivers consistent drainage that is less sensitive to soil compaction and seasonality. Performance is predictable when engineered and maintained.
Maintenance that keeps flow rates high
- Debris control: blow or broom leaves and organics weekly in heavy fall or as needed.
- Fiber and infill care: brush to stand fibers and relieve compaction, top up infill when low.
- Surface rinse: occasional hose-down to move fine silt into the base and prevent surface crusting.
- Drain checks: inspect outlets, channel mats, and weep paths seasonally and after major storms.
Compliance and documentation
Jurisdictions classify artificial turf differently. Some treat it as pervious when installed over permeable bases. Others may require it to be modeled with underdrains or detention. Confirm local rules, document base thickness, aggregate type, and any drains, and keep product drainage data on file.
When to add underdrains
- Clay soils with slow infiltration or perched water.
- Areas trapped by curbs, walls, or grade that limit sheet flow.
- Large catchment areas draining to the turf zone.
- Codes that require a positive connection to a storm system.
Quick spec checklist
- Permeable turf backing matched to site conditions.
- 3 to 5 inch open-graded, washed stone base over a geotextile separator.
- Finished grade at 1 to 2 percent away from structures.
- Edge details that allow water to exit.
- Underdrains where soils or geometry warrant.
- Maintenance plan for debris removal and brushing.
Ready to plan a drainage smart install
FusionTurf supports designs that move water safely and predictably. If you want a site-specific plan, we will help you select the right backing, base, and drainage details for your climate and code.
