About Pervious Parking
Pervious concrete was originally used 100 years ago in Europe as structural insulation in buildings. It has been used as a paving material in Europe for the past 80 years and in the American Southeast for the past two decades with successful results. Since 2001, pervious has been used in Alabama for standard applications such sidewalks and parking lots. Pervious concrete is used for parking lots, driveways, service roads, walkways, sidewalks, curbs and gutters, and secondary roads. It is suitable for light to medium vehicle traffic at low to moderate speeds. It is not suitable for highways or other high speed pavement.
Benefits of Pervious Parking
Eliminates Stormwater Runoff Because of its absorptive qualities, pervious concrete eliminates rainfall runoff. This results in zero discharge of polluted runoff into waterways, lessening of urban flooding, increased groundwater recharge, improved health of adjacent trees, on-site bioremediation of pollutants, and a reduction or elimination of the need for storm drain infrastructure. Pervious concrete negates or lessens the need for unsightly and expensive retention ponds since the product will hold one inch of rainwater (which is the typical rainfall amount).
Reduces Urban Heat Island Effect Because of its light color, pervious helps to reduce the urban heat island effect caused by large areas of dark-colored pavement.
Reduces Paving Maintenance Costs Because pervious concrete requires little or no maintenance, when used as a paving material it can significantly reduce parking lot maintenance costs. An occasional cleaning with a vacuum sweeper truck can help restore void space.
Typical Pervious Parking Installation
Step 1: Pervious concrete is prepared at a batch plant and delivered in a standard ready-mix truck. It must be placed within an hour of mixing.
Step 2: Pervious must be poured from the truck directly into the forms (fig. 2); it cannot be pumped due to its low water content and coarse texture.
Step 3: Once in place, it is leveled with a vibrating screed (fig. 3) and then compacted with a special heavy steel roller (fig. 4). Although control joints are not necessary, in many cases they can easily be made with a flanged roller.
Step 4: The slab is covered with plastic sheeting (fig. 5) as soon as it is completed, and it is allowed to cure under the sheeting for one week.
Step 5: Because of its texture, there is no finishing required. (fig. 6)
Pervious Parking Application Gallery
The principal uses for pervious concrete have been for parking lots, low traffic pavements, and pedestrian walkways.
Pervious concrete’s ability to pass large amounts of water quickly makes it ideal for these applications: drainage media for hydraulic structures, porous base layers under heavy duty pavements, parking lots, tennis courts, and greenhouses.
Its high porosity also gives it other useful characteristics: it is thermally insulating (in buildings) and has good acoustical properties (for sound barrier walls).
a. Parking lots
b. Driveways
c. Service/Secondary roads
d. Walkways, Sidewalks, Curbs/Gutters
Pervious Parking FAQs
Q: Does pervious have strengths like traditional concrete?
A: Autos only place 30 - 50 psi stress on the surface of a pavement and the load "spreading" ability of pervious concrete and aggregate base material reduces the ultimate stress on the sub grade soils to a very low number. Unless the soil is extremely poor, auto traffic loads should be readily accommodated by pervious concrete paving.
Q: Will the surface clog?
A: Coring studies in Florida indicated that, on well-designed pervious concrete parking lots, less than 10% loss of internal volume has occurred due to infiltration of fines after 16 years. Pressure washing has been shown to restore 90% of original effectiveness. Even after intentional clogging, pervious surpassed performance of sod.
Q: How expensive is pervious?
A: Pervious is comparable in cost to decorative concrete. $5.00 a square foot is average, although costs are substantially lower when pervious is placed with a spreader. $3.50 to $4.00 is possible. As installers become more familiar with the installation process, prices should drop. Also, when considering pervious, you are cutting out expensive retention ponds, site development, and land costs. The elimination or reduction in drainage infrastructure often reduces the final cost of the project, making pervious concrete the least costly approach.
Q: What is its lifespan?
A: The lifespan is the same as conventional concrete. Virtually all the pervious concrete installed in the Southeast is still in use. For a free life cycle cost analysis, see our free estimate section of this website.
