Clearing the cracks

Permeable pavers require a little extra attention to ensure they function properly.As permeable pavers begin to make some noise in the green industry, more contractors are thinking about adding the option to their hardscape services.

But what makes the pavers green – gaps between them that allow water to seep through – also creates some maintenance issues. Mainly, those gaps between the pavers can become blocked and affect how the water gets into the ground. Leaves, mud, eroded soil and snow/ice can all clog a permeable pavement.

“The key process for maintaining the maximum possible infiltration rate is vacuuming with either a walk-behind or truck-mounted device that uses regenerative air,” says Patrick Day, product manager for Boral Bricks.

Day says sediment accumulates mostly in the uppermost 1-inch of joint aggregate, making it accessible to clean with a vacuum.

You should vacuum in dry conditions, and if most of the aggregate is lifted out with the sediment, it can be immediately replaced after cleaning. 

“In most cases, a vacuuming of the pavement is either a once-a-year or twice-a-year activity based on the number of potential sediment sources,” Day says. “And only the affected areas of the pavement need to be cleaned.”  

How often the joints need to be cleaned depends on where the pavement is installed and how much traffic it is subject to, says Fred Adams, of Fred Adams Paving Co.

“As an industry, we say that PICPs (permeable interlocking concrete pavers) should be vacuumed swept one to two times per year,” Adams says. “However homeowners can and should blow-off leaves, etc., and keep debris off the surface. One should watch for plant growth or weeds and remove accordingly, typically by hand. It is important to stabilize the surrounding surfaces with grass and materials that won’t contribute to clogging. 

“Even at 80 percent clogged, most of the permeable pavements will still drain at more than 10 inches per hour, and it does not take much to increase that flow when maintenance is performed.”

 Day says even though herbicides may be biodegradable, they may damage the bacteria in the base and sub-base aggregate layers that allow a permeable system to reduce petroleum and other contaminants in the storm water.

“Hiring a vacuum sweeper company or having a maintenance agreement with a sweeping company will become the norm, and can be done for a very reasonable cost such as  fifty cents per square-foot or less depending on the size,” Adams says.

Even if you opt not to vacuum out debris and instead use water to clean put the gaps, you still have to be careful not to use too much power, says Paul Hathaway, president of Pacific Interlock Pavingstone.

“The major concern with maintenance of the gap-style permeable pavers is that if you don’t control the pressure wash psi you will wash the crushed stone out from the gaps and the crushed stone will have to be replenished,” Hathaway says.

Hathaway’s company produces Hydro-Flo pavers, which do not rely on gaps for the permability so there is no stone or crushed rock that might be vacuumed out. 

“The Hydro-Flo area between pavers is so small we suggest the use of very fine sand as the joint filler,” he says.

Hathaway says that a light pressure washer – 1,500 psi – with a fan tip, positioned at a 45 degree angle at a distance of 6 to 8 inches effectively restores the Hydro-Flo paver to full permeability.

However, Hathaway says both the gap-style and Hydro-Flo permeable paver will greatly benefit from regularly scheduled maintenance.

“Even a general sweeping and cleaning off of normal debris will help the surface retain its appearance and permeability,” he says.

Day says if you can’t see the aggregate between pavers, you can perform a simple infiltration field test over any questionable areas.

 “Pour water from a bottle over several pavers and observe how quickly the water infiltrates the joints surrounding those specific pavers,” he says. “If the water does not have to spread out over other pavers to find a way into the joints and supporting setting bed, then the pavement can be considered as functional for managing its designed storm water load.”

The author is an associate editor at Lawn & Landscape. He can be reached at bhorn@gie.net.