Monday, July 19, 2010

Permeable Pavers

Howdy folks! If you've visited the garden lately or read the summer edition of The Garden Leaflet, you know that, with the help of a lot of talented folks, the garden now features a fabulous new hardscape constructed out of permeable pavers, more specificallyTecho-Bloc's "Permea" permeable concrete paving system. For many reasons, we are so excited about this new space. For one, it creates a larger, more welcoming entrance to the garden that more in scale with the rest of the garden. The old one was too tiny...the garden outgrew it. This larger space is also more handicap-friendly and connects the parking lot with the path system throughout the rest of the garden. Additionally, the permeable pavers are ADA compliant. Finally, because we intend to use some of the patio space for containers, the permeable pavers will allow for container run-off(water and minimal fertilizer) to percolate back through the patio and into the earth. Though our patio is a relatively small application of this type of paving material, it is suitable for large-scale projects like parking lots, driveways, boat ramps, and areas that get light residential traffic. Another added benefit, permeable concrete pavers are eligible for LEED(Leadership in Energy and Environmental Design) credits through both the U.S. and Canadian Green Building Councils' specifications.

So, you may be asking yourself, what makes a paver permeable? Well, it's all about the joints and the base, baby. First of all, the pavers have lugs on all sides that interlock with the lugs of neighboring pavers, creating approximately a 7/8" space inbetween all the pavers. This joint is then filled in with a small gravel, #8 aggregate to be specific. This gravel-filled joint space is part of the reason why water permeates so easily through this surface. The second reason why this system is so permeable is because of the base construction. It is excavated by at least 12". That is what we did. For larger scale projects, a deeper base might be spec'd. Then we covered the bottom of the hole with a geo-textile fabric. This keeps the soil and patio fill from settling and seeping into one another. Next, approximately 7" of 57 stone, a coarse gravel, was added on top of the geo-textile (compacted in a series of level lifts). Then, another layer of geo-textile was added. Then came 2" of the #8's to serve as a setting bed for the pavers. The pavers were set in and their joints filled with the #8's. Finally, the whole patio was compacted with a vibratory plate compactor. Voila! There you have it, a permeable patio.

So, that's the quick and dirty of it all. Techo-Bloc provided us with some nice technical materials that I referenced in writing this little tid-bit. See picture below, from said materials, which gives a nice cross-section of a standard permeable patio. Also, check out the link below for some pictures of the kiosk patio being built.

One more thing...if you would like to check out the materials we used for yourself, you can go by Chandler Concrete of Virginia, Inc., located in Christiansburg. They carry the Techo-Bloc pavers as well as the Grotto Hardscapes weathered parapet blocks used for the wall.

Copy and paste into brower, then click 'Play Slideshow'