What you need to know to achieve the best results for your hardscape project

Geogrids and geotextiiles can provide added strength to the base of a hardscape project. (Photo: Green Monster Landscapes)

Before embarking on a new hardscape project, experts say there are several things to keep in mind. Here to help you start your projects on the right foot are Joe Raboine, director of residential hardscapes at Belgard; Jason Arseneau, contractor services manager with Unilock; and Mark Arsenault, principal owner of Green Monster Landscapes in Dover, N.H.

Digging in

Unilock’s Arseneau says contractors should secure all permits and identify any utilities. He says it’s a good idea to communicate with neighbors about any residential projects.

“Letting them know when construction is starting and potential timelines can prove to be helpful,” he says.

Raboine encourages contractors to determine where subsurface water will run, noting that a contractor might need to engineer water flow for complex projects.

“Water flow is probably the most important consideration for all projects,” he says. “Once a proper plan has been created, the last critical item is ensuring that the installation is done per recommendations.”

Raboine says it’s important to know what type of soil the property sits on. It’s even possible there could be two or more soil types. Arseneau says this could impact the excavation needed for a project.

“Free-draining soil types like sand require less excavation, and soil types like clay require more excavation,” he says. “Clay holds onto water, and if your project is in a climate subject to freezing temperatures and freeze/thaw cycles, you would want to excavate more.”

Arsenault says the depth of excavation will depend on the type of project.

“For vehicular traffic versus pedestrian traffic, we’re going to have different standards that we use and different ways of strengthening our base with mechanical means like a geotextile or a geogrid,” he says.

Tools of the trade

Arsenault says Green Monster uses a 3/4-inch open aggregate stone as a base for its residential projects. Green Monster offers residential landscape design/build, irrigation and masonry services. 

“We’ll also use 1 1/2-inch crush stone as well, particularly on driveways, because it has a greater load capacity,” he says. “We’ll also use 1 1/2-inch frequently when we hit poor subsoils, and we have to amend the soil by mixing the stone into it. The 1 1/2-inch has a little bit more body to it.”

Unilock’s Arseneau recommends cement-stabilized aggregates to give the base a boost.

“All of these solutions can help to reduce the overall depth of excavation and provide a good stable base for pavers,” he says.

Building blocks

Experts say a major component of building a strong base is compaction. Unilock’s Arseneau says pros need to compact native soils before adding aggregates.

“When installing your base material either by a slinger or with a skid-steer or even by wheelbarrow, contractors should consider their compaction tools,” he says. 

Arseneau says contractors need to install aggregate in lifts to get the proper amount of compaction.

“If your base buildup is 12 inches total, a contractor can’t simply fill the excavated area and compact down to the 12 inches required,” he says. “Installing in 4-inch lifts and compacting is a good rule of thumb. With the use of larger compaction machines, that 4-inch number can be increased.”

Arsenault says one mistake contractors can make is to overlook the need for moisture in the compaction process, which could impact the project’s lifespan.

“When compacting dense gray gravel, it has to have some moisture in it for it to compact properly,” he says. “It’s not cohesive if it doesn’t have the moisture. If it’s too dry, it’s not going to compact its maximum potential.”

Arsenault says Green Monster goes beyond the Interlocking Concrete Pavement Institute and Construction Products Association standards for base depths and the appropriate amount of moisture for proper compaction.

Raboine agrees that doing more than required is always a good idea.

“When in doubt, install a high-quality geotextile fabric and add more base than what is recommended,” he says. “Be sure to install the base 1 foot past the edge of the pavement. Oftentimes, you see contractors not doing this, and over time the edge will fail, which will cause the whole installation to fail.”