If you’re considering building or replacing a driveway, carport, or other paved area, think twice before you invest in plain old concrete or asphalt. New materials and methods will not only make your property look better–they are better for the environment.
Cool ways to cover the earth
If you’re considering building or replacing a driveway, carport, or other paved area, think twice before you invest in plain old concrete or asphalt. New materials and methods will not only make your property look better–they are better for the environment.
The key is allowing rainwater and snowmelt to drain into the ground, rather than sending them–and all the pollution they carry–into streets and storm drains. Just a 30-by-30 foot patch of concrete can shed over 550 gallons of water in a one-inch rain. Multiply that by thousands of homes, and you’re talking a tidal wave of potentially tainted H2O. Permeable pavement can even lower the temperature around your house in the summertime because, while it absorbs moisture, it absorbs less heat.
Top Tips
Consider your options.Below are some permeable pavement possibilities, from very inexpensive small stones to pavers and even driveways and carports made of grass.
Small stones. These are the least expensive, and allow water to penetrate, but require more frequent maintenance because little stones are easily displaced. NOTE: By “stones,” we mean smooth stones, not crushed gravel, which lets water run off instead of down in the ground.
Grass. Yes, it’s possible to turn asphalt or concrete into lawns. This is achieved by sinking a durable plastic grid into the ground and letting the grass grow in it. Vehicles can be driven on it, just like on a driveway, but if they are parked for extended periods of time, the grass won’t grow.
Pavers. There are good-looking interlocking pavers that fit together like puzzle pieces but that have sufficient gaps between them to allow water to seep down into the ground.
Hollywood driveway. This old standby is well worth considering. Instead of a solid run of asphalt or concrete, it consists of two narrow, parallel strips of concrete, spaced so that a vehicle’s wheels can drive on them. Water soaks into the vegetation beside these strips. This type of driveway will be cheaper than solid concrete because less concrete is required. If the path is extremely long, however, it may be hard to follow, so drivers’ skills must be taken into account, especially if long backups are involved.
Pervious (permeable) concrete. Made by using less fine material in the concrete mix, perious concrete is durable and porous. Contact local contractors to see if they are familiar enough with this material to do an installation.
Porous asphalt. This type of asphalt works on the same principle as the perious concrete described above. It, too, is durable, but should be installed by an experienced contractor.
Other Considerations
The following is a rough guide to the per-square-foot costsof materials when installed professionally:
Pervious concrete: $4 to $8
Porous asphalt: $4.60
Grid systems for grass: $5 to $6.50
Pavers: $12 to $15
Concrete lasts longer than asphalt in warmer climates, but asphalt lasts longer were the weather is cold. A rougher surface, such as small stones, can make snow removal more difficult, so you may have to consider a tradeoff between cost and convenience.
If anyone in your household uses a wheelchair, remember that a rougher surface hinders accessibility.
Benefits…
…to you
Permeable pavements create better-looking, cooler areas around your home.
…to the Earth
Stopping runoff prevents pollution. When water is allowed to seep underground on site, on the other hand, it is purified as it descends.
Common Mistakes
Not preparing the subsurface properly. Regardless of the pavement or surface you choose, you must make sure that there is a solid yet porous layer underneath.
Ignoring local conditions. There is no single solution for pavements, so consult reputable contractors to find out what will work best.
Building on heavy clay. Heavy clay is so impermeable that it may not be worthwhile to place a permeable surface on top of it. Consult a local engineering firm or reliable contractor if this is a concern.
Going too close to a well. Water that is allowed to seep deep into the ground is purified as it trickles down through layers of soil, sand, and porous rock. However, if your well is close by, you may have no choice but to allow water to drain off to avoid contamination.
Getting Started
Check your local building codes to see what is permissible in your location.
