Landscape Architect Articles

2008 March LSMP Site Surfaciing: Grid Pavers Can Add Green06-06-08 | News

Grid Pavers Can Add Green

By Michelle Brown, consultant to Pavestone Company

The concrete jungle does not have to be gray. Superintendents have an option that allows them to implement a little green into areas that have traditionally been constructed from poured concrete such as driveways, emergency fire lanes and median crossovers. Look no further than open-celled concrete or ?EUR??,,????'??grass?EUR??,,????'?? pavers.

Open-celled concrete pavers?EUR??,,????'??+sometimes called grid pavers or grasstones?EUR??,,????'??+ are made with an open-void or lattice design. They consist of a flat surface that forms a continuous pattern of concrete when installed. The concrete grid reinforces grassy areas that are subject to pedestrian or vehicular traffic, while the open void allows for on-site infiltration of storm water and revegetation. Thus, the area has less thermal heat gain and is less subject to damage from water runoff and pollution, creating a very environmentally-sound project.

Putting topsoil and grass in the grid openings to produce the desired effect. As a result, you have the flexibility to construct required pavement applications that allow for attractive green landscaping instead of ordinary poured gray concrete.

Concrete Grid Pavers: Intermittent Use ?EUR??,,????'??? Heavy Loads

Proper maintenance is necessary in order for the landscaping to thrive. ?EUR??,,????'??As with any living area, irrigation and maintenance are required to keep plantings green,?EUR??,,????'?? says Richard Bodie, Vice President of Commercial Sales, Pavestone Company. ?EUR??,,????'??Appropriate grassy species selection, frequent watering, fertilizers and weed control are required if the objective is to have a successful grassed area.?EUR??,,????'?? In addition, Bodie says that partial defoliation from repetitive traffic and high ambient temperatures can be expected.

Open-celled concrete pavers are a great option for overflow parking projects. Other proven applications include lakeside and slope surface stabilization, minor ditch lining, driveways, parking structures, emergency fire lanes, overflow parking and median crossovers. Most residential use has been for driveway ?EUR??,,????'??runners?EUR??,,????'?? where the units are placed in two parallel bands that support the vehicle directly underneath the wheel paths.

The products are made from a ?EUR??,,????'??no slump?EUR??,,????'?? concrete mix. Manufactured under extreme pressure and high frequency vibrations, they have a compressive strength greater than 4000psi, and a water absorption maximum of 7 percent. The units?EUR??,,????'??? surface area sizes range from one to two total square feet. The product is typically three, four inches and six-inch thicknesses in availability. Unit shapes are either rectangular or geometric interlocking figure eights. The geometric shape is preferred for vehicular traffic as it may restrict lateral creep of individual units. Rectangular shapes have been used to provide a stable surface that is capable of growing grassy plant species in the open cells within the body of the unit.

Like any other paving surface material, civil engineering considerations have to be taken into account. Issues such as existing soil strength, sufficient dimensions of structural base materials for the traffic design loads and site specific environmental conditions have to be addressed for the product to perform structurally.

When installed as a pavement, unsuitable, unstable or unconsolidated sub grade material should be excavated and then compacted according to the direction of the landscape architect who is directing the project. Backfill with compacted, dense, graded aggregate to a minimum 4 inches (100mm) to 12 inches (305mm) or as directed by the landscape architect. The paver units are then placed on a thin, compacted layer of not more than 1/2 inch (13mm) of sand.

Erosion control applications (ideally to a 3:1 or more gentle slope) require the slope to be uniformly graded before bedding the paver units in a maximum 1/2-inch (13mm) layer of sand. To prevent the migration of fine granular material, it may well be necessary to place a geotextile on the graded slope before applying the bedding course of sand.

In order to support grass or plant growth, the voids must be filled flush to 2 inches to 3 inches above their surface with suitable topsoil or mixture of soil and fertilizer. Then the openings are seeded, sprigged or plugged.

When your project calls for a pavement application, consider open-celled concrete pavers. Add a touch of green to the concrete jungle with a product that is a proven solution.