Asphalt installation should be applied to a graded base. Due to the soft and constant moving soil we deal with in the west, a sand/aggregate base (base course) is used to strengthen and support the asphalt.
An asphalt overlay is the installation of a layer hot mix asphalt to the existing asphalt surface. Pavement that have large areas of failure (alligatored cracks), but is structurally sound is ideal for asphalt overlay. The existing asphalt must be prepped and repaired before the overlay can be installed. These repairs can include, crack repair, pothole and patch repair. After the necessary repairs have been made tack coat is applied to maximize adhesion of the new asphalt to the old asphalt. The new asphalt is laid down and compacted, usually at 1 1/2" to 2". Asphalt overlays are cost efficient and provide a fresh, new surface for tenants and traffic.