Permeable Pavers Help Put Water In Its Place

Filed in Landscaping by on June 30, 2014

permeable paversManaging storm water is a big deal on lakeshore properties. Excess water running too fast can cause erosion and send pollutants into our lakes. Landscaping with permeable pavers is one way homeowners can help control the flow of water on their properties.


A permeable paver system uses a combination of crushed rock and gapped pavers to allow water to drain into the ground below, rather than running off the surface. Neil Jensen, vice president with Alex Brick and Stone in Alexandria, says the jagged-rock base is integral to the functionality of the system.


Larger rocks go at the bottom, then comes a layer of smaller rocks. The pavers are placed on top with small rocks between the individual blocks. Water doesn’t pass through the pavers themselves but slips through the cracks between. Many styles of permeable pavers include spacers to ensure the right-size void is created, but regular pavers can work with a permeable system if spaced correctly, says Jeff Timm of Werni Timm & Associates in St. Paul.


The depth of the base depends on the type of soil below and the expected level of traffic above. Jensen says typical driveways in Alexandria have a 12- to 15-inch base and can easily handle regular residential traffic. Sandy soil will require less rock depth and sometimes also pipe drainage.


permeable pavers patio surfaceInstalling the rock base is time-consuming and makes a permeable paver system more expensive than regular pavers, says Matt Hoen, owner of Outdoor Renovations Landscape & Nursery in Underwood. Jensen estimates the cost at 20 to 30 percent more and adds that the type of rock used for the base can affect the price.


Besides cost, there are a few drawbacks to using permeable pavers. One is that manufactures don’t offer as many styles and colors as are available for regular pavers. Some of the older styles of pavers have a hole in the middle to let water pass, but newer ones keep the gap on the outside, making them easier to walk on, especially in high heels.


Another concern is maintenance. Caring for a permeable paver patio or driveway generally involves sweeping or blowing off debris monthly, Jensen says. While this is not much different than the maintenance for any other surface, letting weeds or debris fill the spaces will impair a system’s effectiveness, so homeowners have to be vigilant.


But there are clear advantages to using permeable pavers. The systems prevent storm water runoff, which is a practical solution as well as an ecological one. For example, if your property has a heavy slope and water is running into your house or garage, replace your old impervious driveway or patio with permeable pavers  will help keep water out of these structures. “You can use them to your own benefit,” Jensen says.


(Timm warns that it’s important to be sure the base drains away from the house or garage.)


And in many counties, permeable pavers give homeowners flexibility in adding driveways and patios to their lots. Counties generally regulate the percentage of a lakeshore lot that can be covered by an impervious – 25 percent, for example in Douglas and Otter Tail counties. A large house easily could cover the maximum space allowed, before a driveway or patio is built.


permable pavers driveway“(Permeable pavers are) a great solution to be able to build on some of these less desirable lots that are too small,” Hoen says, because in some counties, a percentage of the permeable pavers’ surface area is considered pervious (allowing water through), thus reducing the total impervious area.


For example, Douglas County counts 25 percent of the permeable pavers’ area as pervious, provided the system is installed correctly and a maintenance plan is set out. In certain cases, 100 percent of a paver system could be considered pervious.


Otter Tail County takes a different view, however. Bill Kalar, director of  the county’s Land and Resource Management Office, says no percent of the paver system is considered pervious there. He cited several reasons, including concerns that improper installation or maintenance could make the system ineffective.


Not least of the county’s worries is aesthetics – giving credit for permeable pavers means allowing more of a property’s surface to be covered. “At this point, I’m not convinced that they’re the best thing for the lakes area, Kalar says.

till choosing permeable pavers because they’re trying to be eco-conscious and because they believe the systems work. He does, too.


Jensen agrees: “It’s going to be a practice that will stay with us for a while.”



by Emily King






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