What is a paving grid?

enlarge this image

Permeable paving in Missouri Botanical Garden parking lot allows water to reach tree roots. 

Like installing snowshoes in your lawn

Also called permeable pavement, soil reinforcement grid, open celled paving grid, and porous paving matrix. Surfaces covered with these materials can be planted and bear weight without compressing. The grid is made of a material with regularly interspersed voids, where the voids are filled with permeable materials such as gravel, sand or soil and plants. Used in parking lots and heavy foot traffic areas in botanical gardens and public parks, for erosion control under paths over fragile soils, for green driveways and emergency vehicle access routes through natural areas.

Imagine slicing the tops and bottoms off of soup cans, then slicing the cans to create two or three open cylinders from each can. Now arrange those cylinders on the ground, side by side like a honeycomb with cylindrical cells. Fasten the cells together. Fill in and between all the cans with loose soil. Plant grass seed or a foot-tolerant groundcover. Or fill with small stones and don't plant. Walk or drive there. The mat of cut soup cans takes the weight. The plants' growing space or the soil around tree roots below the grid remains loose.

It is sold in rolled mats or flat modules and may be made of concrete cells, rigid plastic cells or composites. In our area it's a known- but non-stocked item at landscape material supplies company. We ask, the supplier orders it in for us. Be prepared to describe the grid, as we have here -- take our illustration with you! -- because it's relatively new and goes by various names.

Below: We noticed the grid of permeable paving on a recently renovated slope at Chicago Botanic Garden. (Rings visible near Janet's foot.)


Below: That same slope at Chicago Botanic's Dwarf Conifer Garden, four years later, grass healthy and the slope still attractively green despite heavy foot traffic.


Below, left: The concrete grid in Missouri Botanical Garden parking lot is gravel filled, but in sunnier, less heavily trafficked areas the same kind of grid might be filled with soil and seeded (below, right).

MoBotTrGrid9673s.jpg  PavingGridSeattle.jpg

Permeable paving performance test, results, University of Washington

Take a look at more types of paving grids manufactured by various companies, and a video of paving grid installation.

Consider a DIY (do-it-yourself) grid of stepping stones with ground cover between. It's in Growing Concerns 575: Ground covers


 Simple Box Green With White - Sponsor