While pavers can be used to create a focal point in a backyard or elegant designs in a driveway, the functionality of permeable pavers appeals to customers as well.
“Even since the 1990s, these pavers have really taken off,” says David Smith, technical director for the Interlocking Concrete Pavement Institute. “That was when the EPA was tasked with coming up with ways for municipalities to handle stormwater runoff.”
The EPA produced a list of best practices for stormwater management, and on that list was a recommendation for the use of permeable pavers. From there, the industry took off, Smith says.
Smith says permeable pavers are currently the most common type of concrete paver, as they allow water to permeate through to the ground.
A paver is considered permeable because of the spacing between the joints, which is set by the manufacturer when the paver is created. The spacing is filled with a coarsely ground gravel that allows water to flow through.
“The spacer bar is larger with permeable pavers,” says Joe Raboine, national design and training specialist for Belgard. “This allows water on the surface to permeate through the joint and into the ground.”
Several types of stone are layered to create the base of the paver installation, all of which are permeable to a degree. The only part of a permeable paver installation that doesn’t facilitate water flow is the paver itself.
“The actual paver is solid,” Smith says. “The water runs off that and into the joints where it can permeate through.”
In a typical permeable paver, the joints allow nearly 100 inches of water to flow through per hour.
For some properties, permeable pavers are a requirement. Some cities require properties to have a certain percentage of permeable area on the property when installing any type of concrete.
“There’s more momentum to use permeable pavers with residential clients,” Raboine says. “Along with municipal requirements, in the West and Southwest, (permeable pavers) are used to assist with irrigation.”
Carl Peterson, director of education for Nicolock Products and instructor for ICPI, says in some cases a property is only allowed to have 50 percent impervious coverage.
“Permeable pavers help alleviate those restrictions,” he says.
Using permeable pavers around areas like in-ground pools, where there is typically a large concrete surface, can increase the percentage of pervious area while providing a practical solution to a wet pool deck.
Smith says some municipalities even offer rebates for the installation of permeable pavers to combat runoff issues and habitual floods. “Oftentimes, the rebates are cheaper for the city than having to upsize a storm drain would be,” he says.
One of the most common mistakes contractors make is using a slab for installations like driveways or parking lots, instead of a paver, Peterson says.
A paver is 101 square inches or less, whereas a slab is larger – typically 12 feet by 18 feet or larger.
“A concrete slab (is better suited) for those pedestrian uses, like sidewalks or backyard patios, but not for any type of vehicular use like a driveway,” Peterson says. The weight of the vehicle would be too much for the concrete slab, and could cause complications over time, like cracking.
Pete Baloglou, director of education for Techo-Bloc, says contractors need to be mindful of a few technical decisions before installing the pavers.
“A big mistake that (contractors) can make is not taking in the runoff from surrounding slopes,” Baloglou says. “You might be installing a patio that is 1,000 square feet, but if you have 5,000 square feet of grass sloped right to it, that’s a problem.”
To avoid excess runoff issues, Baloglou recommends using edge restraints in almost any applications. These restraints are raised around the edge of the installation area, and cause any water on the surface to be contained within the installation area. They also work to keep excess water out and avoid a phenomenon known as “creep.”
“Creep is the horizontal movement of pavement under load,” he says. “This is how some installations will start to fail.”
In some cases, permeable paver installations may not be the best option. Any installations that need to be built right next to the foundation of a building should be installed with something other than a permeable paver.
“You don’t want water being directed right to your foundation,” Baloglou says. “Permeable installs should be done 6 feet to 9 feet from that foundation wall.”
He also suggests contractors use geotextile liners when they begin building the base layers of their installations. Raboine says the type of soil at the site will also impact the way a contractor installs the pavement.
“Heavy clay soil would cause the water to sit underneath the (installation),” he says. “So, you would want to take the time to excavate more of the soil and add more gravel to the base.”
Smaller areas are typically more expensive to install, Smith says. Larger areas allow for the use of a machine to lay the materials, whereas small areas will have to be installed manually.
Raboine has noticed an increase in the popularity of pavers with clean lines. Customers are looking for pavers with sleek lines for a modern look.
“Any paver can realistically be made to look modern and clean,” he says. “But the No. 1 paver we see is still those rustic natural stone-looking designs.”
Another trend contractors are seeing is the use of multiple styles and colors of pavers to create a more artistic and creative design.
“We are seeing a mix of styles,” Raboine says. “A lot of people are looking for that modern farmhouse-look right now.” The use of porcelain has been gaining popularity among residential clients as well, but they are a more expensive option.
Once a permeable paver installation is completed, there isn’t much upkeep required. The pavers will be exposed to outside elements like rain, snow and debris, but there isn’t a high risk of damage with those occurrences.
“The main thing you want to be aware of is the joints,” Smith says. “Just picking leaves off every now and then so that they don’t get stuck in the joints.”
Because the joint spaces are what allows the water to flow, you can instruct clients to look out for a buildup between the pavers.
“Driveways get dirt tracked on to them,” he says. “It happens. The trick is to keep (the water) infiltrating that soil.”
Smith says in some cases the pavers may need to be vacuumed with a shop-vac once a year. “It’s like a filter, and you have to clean out a filter every now and then.”