Bay Area Pervious Concrete was recently asked to install our decorative exposed aggregate pervious pavement in the parking areas of a high-end residential project. The driveway itself was a beautiful 2’ x 2’ Italian stone and was designed to be permeable. To achieve this, the landscape contractor used a Class II permeable base and then mortared directly on the base to set the stones. The bed of mortar was carefully placed so as not to fill the spaces between the stone, creating a passageway for surface water to pass through to the base rock.
Natural stone with permeable grout
This space was then filled with a product known as PerkGrout, which is essentially a form of pervious concrete with a sand-like aggregate. The finished pavement looked beautiful and as you can see in the demonstrative video, was highly permeable and allowed water to pass through quite easily.
However, our portion of work had not yet taken place and unbeknownst to us, challenges lay ahead. Since the stones were not mortared to a concrete slab as is typical for a vehicle-rated application, they were not able to handle heavy loads. We originally intended to bring the concrete ready-mix truck through the driveway to access our work areas, but the general contractor warned the driveway could not handle the weight and our installation process was modified accordingly. Consequently, our crew resorted to concrete buggies to bring material on-site. This was not only a problem for us – all large vehicles had to park along the street, including the homeowner’s moving vans!
Reflecting on this challenge and inspired by a design used for pavers by our good friend Brian Lutey in the Chicago area, David Liguori came up with a new detail (see below). This detail utilizes pervious concrete as the base for the stone, providing a strong and stable system with the capacity to handle heavy loads, while still providing permeability. In addition, typical permeable paver or stone designs use loose stones or decomposed granite as the grout material, which eventually spills out, is washed out, or leads to vegetation growth between stones requiring a high level of maintenance. By eliminating this mess our design not only keeps the pavement clean, but also reduces maintenance costs, talk about a win-win!
Our products are designed to withstand all the elements to ensure longevity and durability. If you would like to utilize this system on your project, please feel free to reach out to us for design assistance.
As always, all of our specifications and details are available for download and free to use. The following link also includes a series of white papers covering topics ranging from pervious concrete mix design, pervious concrete and water quality, to rebar in pervious concrete.
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