How Thick Should an Asphalt Driveway Be?
The Colorado Asphalt Pavement Association's best-practices brief recommends a base of 6 to 8 inches of crushed aggregate under an ordinary residential driveway, topped by a 2-inch asphalt bottom course and a 1.5-inch surface course. For an overlay on an existing driveway, it says 1.5 to 2 inches of surface mix is usually sufficient.
The base: 6 to 8 inches of crushed aggregate
The Colorado Asphalt Pavement Association's brief, published through the Asphalt Institute, says a base course of 6 to 8 inches of crushed aggregate is usually adequate for a residential driveway. Under it, the subgrade should be graded smooth, cleared of organic material, and have weak spots undercut and replaced with suitable material.
The asphalt: two courses
For best results, the same brief says the ordinary residential hot-mix driveway should consist of a 2-inch bottom course covered with a 1.5-inch surface course, placed by machine and compacted with proper rollers.
Overlays on an existing driveway
For a driveway that is being overlaid rather than rebuilt, the Colorado Asphalt Pavement Association says 1.5 to 2 inches of surface mix is usually sufficient, after weak spots, holes and large cracks are cut out and patched, and with a tack coat on old weathered surfaces.
Put it in writing
The National Asphalt Pavement Association says a professional driveway contract should include the thickness of the pavement, responsibilities for site preparation and drainage, the payment schedule and a clear warranty.
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Sources
- Colorado Asphalt Pavement Association (via the Asphalt Institute), “Best Practices” for the Use of Asphalt Driveways, Technical Brief
- National Asphalt Pavement Association, Hiring an Asphalt Contractor for Driveways
Frequently Asked Questions
The Colorado Asphalt Pavement Association says a base course of 6 to 8 inches of crushed aggregate is usually adequate for a residential driveway.
The Colorado Asphalt Pavement Association recommends a 2-inch bottom course covered with a 1.5-inch surface course for an ordinary residential driveway.
According to the Colorado Asphalt Pavement Association, an overlay of 1.5 to 2 inches of surface mix is usually sufficient.