Permeable grass and gravel grid system being installed at the UGA Green Stormwater Infrastructure demo site

Stop 1: Grass & Gravel Grid

Overview

Pervious grid systems use interlocking plastic frames to create stable, load-bearing surfaces that allow rainwater to soak into the ground below. Filled with gravel or planted with turf grass, these systems serve areas with moderate foot or vehicle traffic while maintaining permeability—reducing stormwater runoff, erosion, and flooding.
Practice Type: Structural surface infiltration with flexible fill options

Quick Facts

Fill OptionsPea gravel, shell, or turf grass
ApplicationsParking areas, walkways, patios, overflow parking
Subsurface Storage6+ inches of #57 stone reservoir with 40% void space
Added BenefitReduces heat radiation compared to concrete or asphalt
Cost Range$6 to $16+ per sq. ft., including all materials and labor

The Problem

Many landscape areas need stable surfaces that can handle foot traffic, light vehicles, or heavy use—but conventional concrete and asphalt create large impervious expanses. These surfaces generate significant stormwater runoff, radiate heat during warm months, and often eliminate green space that could otherwise absorb rainfall.

The Solution

Pervious grid systems provide structural support while keeping the ground permeable. Various plastic grid products are designed to withstand different weight loads depending on the intended use. Typically, grid systems are used in multi-use areas with moderate foot or vehicle traffic, such as parking spaces or walkways. For aesthetic purposes, small pea gravel, shell, or turf grass can be used as the final surface and is stabilized by the durable plastic grid frame.

How It Works

Interlocking plastic grid panels are placed on a prepared base of compacted stone and bedding material. The grids create a structural matrix that distributes weight evenly across the surface while maintaining open cells that allow water to pass through. Beneath the grid, layers of angular stone provide temporary storage and allow stormwater to slowly infiltrate into the underlying soil.

Design Specifications

Sizing Example

A 160-square-foot impervious surface (such as one parking space) will produce about 13 cubic feet of water during a 1-inch rainfall event. A pervious grid system with a 3-inch-deep reservoir of proper stone (1.5- to 2.5-inch diameter gravel, or No. 2 stone) with 40% void space will capture all of that stormwater and allow it to slowly soak into the ground.

System Layers (Top to Bottom)

  • Interlocking plastic grid panels filled with gravel, shell, or loam soil for seeding grass
  • Optional 1-inch bedding layer of fine sand
  • Geotextile erosion fabric
  • Compacted sub-base of clean angular 1.5- to 2.5-inch stone (No. 2 stone) at 6 to 12 inches deep
  • Thin plastic geo-grid or erosion fabric at subgrade level
  • Prepared subgrade soil with adequate infiltration rate

Try It Yourself

Pervious grids are ideal for homeowners looking to create stable parking areas, reinforce erosion-prone lawn sections, or build attractive walkways without adding impervious surface. The grass-filled option is particularly popular for overflow parking areas that need to remain green, and the gravel option works well for patios and low-maintenance walkways.

For Professionals

Some stormwater mitigation projects required by government agencies for new construction permits may need different depths or volumes for stormwater storage, which will be determined by the agency and stormwater engineers. The Georgia Stormwater Management Manual, Volume 2: Technical Handbook (2016) provides detailed specifications for pervious surface systems.

Resources

Download fact sheets, design guides, and technical resources for this practice.