What “permeable” means for permits

Permit reviewers care about whether rainfall infiltrates to soil or runs off to a storm drain. Permeable surfaces allow water to pass through and infiltrate. Impervious surfaces shed water. Synthetic turf is evaluated as a complete assembly: turf backing, infill, base, and subgrade.

When synthetic turf qualifies as permeable

  • Installed over a free-draining, open-graded aggregate base that stores and infiltrates stormwater.
  • Turf backing is perforated or fully permeable, allowing vertical flow through the surface.
  • Edges and seams do not trap water. No concrete toe-ups or continuous borders that create a dam.
  • Subgrade has infiltration capacity, or the design includes an approved infiltration or detention approach consistent with local code.
  • Documented infiltration performance and a simple maintenance plan to keep pores open.

Typical permeable turf assembly

  • Synthetic turf with perforated or permeable backing.
  • Clean, well-graded infill that supports drainage and surface stability.
  • Open-graded aggregate base sized for load and storage. Commonly a washed stone layer with high void space.
  • Optional nonwoven filter fabric if required by soils, selected for high permeability and clog resistance.
  • Subgrade prepared to promote infiltration, not overcompacted. Underdrain only if soils demand it and local code accepts the approach.

Backing and infill considerations

  • Use turf with published drainage data. Review hole pattern or permeable backing specs.
  • Select infill that does not introduce fines that could clog the system.
  • Maintain consistent grade. Provide a slight slope to prevent ponding while preserving infiltration.

When turf is not counted as permeable

  • Installed over concrete, asphalt, waterproof membranes, or a sealed base without an engineered blue-green roof design approved by the jurisdiction.
  • Dense-graded or compacted base that blocks infiltration.
  • Edge restraints or curbs that trap water and force runoff to drains.
  • Clogged systems where debris and fines prevent water from passing through.

How to document permeability for your permit

  1. Confirm the local definition of pervious surface and any required test methods.
  2. Provide a cross-section detail showing turf, infill, backing, base gradation and depth, fabric, and subgrade prep.
  3. Include turf product data showing backing permeability or drainage characteristics.
  4. Specify base materials and gradations, thickness, and storage volume assumptions.
  5. Provide infiltration testing for subgrade or the installed assembly if requested. Common methods include ASTM C1701 or double-ring infiltrometer testing.
  6. Add hydrologic calculations that show reduced impervious area, infiltration capacity, and peak flow impacts based on local modeling standards.
  7. Attach a simple maintenance plan to preserve permeability.
  8. If replacing hardscape with turf, highlight the net reduction in impervious cover.

Data reviewers expect

  • Site plan with limits of turf area and slopes.
  • Section detail with materials, thicknesses, and notes on compaction and geotextiles.
  • Material cut sheets for turf and backing permeability, plus base gradations.
  • Infiltration test results or references to local soil data if accepted.
  • Hydrology method used and assumptions. Show calculations clearly.
  • Maintenance tasks and frequency to prevent clogging.

City-by-city differences to expect

Policies vary. Some jurisdictions always treat synthetic turf as pervious when installed over an open-graded base with proof of infiltration. Others require on-site testing or treat turf the same as landscaping. A few default to impervious unless the full assembly meets explicit permeable pavement criteria. Call your reviewer early, cite their code, and show your details.

Rooftops, decks, and podiums

Turf over a waterproofed structure is not pervious in a stormwater sense unless the assembly is designed and approved as a blue-green roof with storage, controlled release, and overflow. Use drain mats, reservoir layers, and a stamped design if required. Get written confirmation from the authority before counting it as pervious.

Fast-track submittal checklist

  • Local code citation for pervious classification.
  • Plan and section details of the turf assembly.
  • Turf and backing permeability data.
  • Base gradation, depth, and storage volume.
  • Infiltration testing or accepted soil data.
  • Hydrologic calculations and assumptions.
  • Maintenance plan and responsible party.

Maintenance to keep it permeable

  • Remove leaves and debris regularly.
  • Groom the surface to lift fibers and open pore space.
  • Replenish infill as needed to maintain performance.
  • If clogging occurs, surface clean or vacuum and restore the base surface as specified.

Work with FusionTurf

We speak permit. Tell us your jurisdiction and goals. We will match products, provide clear cross sections, and assemble the documentation your reviewer wants. No fluff, just specs that pass.