Q: I need to have my driveway redone. Is there a surface more environmentally friendly than asphalt or concrete?
—Lisa Matthews, Madison, N.J.
Troy Johnson of Outdoor Escapes replies: The best way to green up a driveway is to install permeable pavers, which allow water to drain down through the gaps between them and into a bed of crushed stone. From there, it seeps gently into the soil. Contrast that with a typical driveway, where water picks up oil and other chemicals as it washes into the street, overloading storm drains, polluting waterways, and increasing the chances of flooding from runoff.
The pavers are made of brick, stone, or, like here, concrete, but they'll work only if laid over a properly installed base. For a job of this scale, hire a pro with permeable-paver experience; smaller projects, like a path or patio, are fair game for DIYers. Either way, regular maintenance is a must: Plan on sweeping or vacuuming the joints at least once a year to prevent them from becoming clogged with leaves and debris and acting just like your old driveway.
Shown: This driveway can absorb at least 10 inches of rain per hour, about twice the intensity of the heaviest 100-year downpour in the U.S.
Steps on How to Install a Permeable Paver Driveway
1. Test the Soil and Excavate
First, call 811 for an underground utilities check. Next, do a percolation test to see how fast the soil absorbs water. (Contact your local Cooperative Extension office for details.) Remove the existing pavement, and dig to a minimum depth of 15 inches, unless the perc rate is less than 0.52 inches per hour. In that case, you may need a deeper base or drainage pipe.
2. Prepare the Stone Base Layers
Cover the excavation with a 6-inch layer of ¾- to 2-inch washed crushed stone, which has sharp edges that knit together. (River gravel, with its rounded profile, is unacceptable.) Go over it twice with a plate compactor, across and lengthwise. Top with one 4-inch layer of ¼- to 1½-inch washed crushed stone, and compact that twice, too.
3. Screed the Bedding Layer
Install a concrete or hard-plastic edging to keep the pavers from shifting. Then, starting from one corner, lay two 2-inch-diameter steel pipes about 6 feet apart and parallel on the compacted base. Cover them with ¼-inch stone, then pull a 2x4 screed board over the pipes to create a flat bed for setting the pavers. Lift out the pipes, fill the gaps, and repeat across the remaining area.5.
4. Place the Layers
Starting at the lowest corner, set the pavers on the bedding layer, tight to the edging and one another. (Nibs on the sides of the pavers automatically create the drainage gaps.) Check every 6 to 10 feet to make sure the pavers are square to the first row. Place all the full-size pieces, then go back and cut pieces to fit in any gaps along the edges.
5. Fill the Joints
Once the pavers are in, sprinkle ¼-inch stone, the same used in Step 3, on the surface, and sweep it into the gaps with a wide push broom. Push the broom diagonally across the grid so that you don't dislodge any stones already in the joints.
Sweep the surface clean, then run a plate compactor diagonally over the entire driveway. The machine's vibrations pack the pavers firmly into the bedding layer and lock them in place. Refill joints that have settled deeply, and compact again. Now your driveway is open for business, rain or shine.