An asphalt overlay is a layer of new asphalt applied over the existing base layer of asphalt on a driveway, parking lot or road. These new layers are generally about 1.5- to 3-inches thick, depending on the demands on the asphalt and the depth of surface asphalt removed. An asphalt overlay should not be considered an adequate alternative to repaving in every case, but it is a way to significantly extend the useful life of your paved surfaces if the base of your pavement is still in good shape.
As opposed to simply patching potholes, an asphalt overlay is used for both new construction and old construction in terms of pavement maintenance. Overlaying a project takes place after (1) milling up the existing asphalt and “overlaying” it with new asphalt and (2) when a new project is being built, it is customary to “overlay” new asphalt on top of whatever stabilized subgrade the project in question calls for. An overlay is going to provide smoother, more consistent results than simply patching potholes.