Driveways – Asphalt
Asphalt is easily shaped, flexible and durable, and often very cost effective to install. Because asphalt is designed to give without losing any strength, it will withstand many years of freeze-thaw cycles without compromising appearance or durability. The black color of a typical asphalt surface can mask oil spills and other stains that would be readily apparent on other surfaces. Asphalt’s dark color can also promote melting of snow or icy buildup on the driveway—a bonus for homeowners in colder climates.
Properly installed, an asphalt driveway can last decades. The key to a durable asphalt surface is a well-prepared base. The soil beneath the driveway should be strong and firmly compacted before asphalt is poured. Traditionally, asphalt surfaces have been installed on a base of crushed angular gravel, or aggregate. The thickness of the aggregate depends primarily on the quality of the base soil and the expected usage of the driveway. Most contractors recommend an aggregate base of four to six inches for residential purposes.
Where possible, the strongest and highest-quality option is full-depth asphalt. This means that the entire driveway—from the compacted earth on up—is constructed of the asphalt mixture. According to the National Asphalt Pavement Association, one inch of asphalt is equal in strength to three inches of aggregate. Because the asphalt is poured directly onto the soil base, a full-depth installation uses less material but results in a stronger, more durable surface. A residential driveway is typically constructed with a minimum of four inches of asphalt; some contractors use up to six inches if the driveway will accommodate vehicles of varying weight. The completed surface should have a slope of at least one quarter inch per foot to prevent problems with standing water.
Asphalt must be installed when the mixture is hot. Cold weather can decrease the amount of time the contractor has to spread and compact the material, making the process difficult. Homeowners in warmer climates will have more opportunities for asphalt work, while those living in colder climates should plan to have asphalt installed in the summer.
Nine months to one year after the installation, an asphalt driveway will need to be sealed for the first time. Sealing will protect your driveway from the effects of oil, weather, and salt. However, the sealant is merely a coating and, as such, does not last forever. To maintain the integrity of the driveway, it should be resealed every two to three years.
Inspect your driveway at least once per year. Any cracks that appear should be repaired as quickly as possible. Besides aesthetic concerns, cracks in the surface—even hairline ones—can admit moisture, which will erode the asphalt surface.