Permeable Surfaces

Hardscape Specialists








  1. Managing Director
Permeable Surfaces

Pervious or permeable is part of stormwater management. It is a system or method of installation that allows rainwater to percolate into the soils and replenish the water table the way mother nature intended. So much of our cities have been covered with impervious asphalt and concrete that much (too much) of our rainfall is funneled into storm drains and then dumped untreated into the oceans and lakes. More and more, local municipalities (such as Isle of Palms and Sullivans Island in South Carolina) limit the amount of lot coverage that can be impervious, this includes the footprint of the house, your driveway, and walkways, swimming pool and patio.

So, how does a pervious installation differ from a traditional stone or paver surface? It's all about the sub-grade. Instead of a compacted limestone base that does not allow for infiltration, a pervious base is made up of washed gravel like granite. Mostly it is an elaborate French drain. After the granite is appropriately installed the pavers or stone are set on top, but because the stone or pavers are not themselves pervious, there has to be a space between each paver to allow the water to flow into the base. The space between each paver is filled with smaller, loose gravel. Loose gravel, by itself, has its drawbacks: loose gravel tends to "migrate" out of the joint and onto the surface; it can be unsightly and uncomfortable under bare feet; loose gravel also makes an excellent home for unwanted weeds and insects. Charleston Cobble Company has a unique solution to this problem. We use EcoSystems grout. It is a two-part binder that can be mixed with sand or gravel that is swept into the joint that then stabilizes and hardens. The proprietary formula allows for infiltration rates that meet or exceed local building codes.