Asphalt overlay or mill and overlay?
An asphalt overlay is a new layer of hot-mix placed over existing pavement that is still structurally sound. A straight overlay raises the surface, which works in open areas but not where the pavement meets curbs, drains, doorways, or a garage. There we mill first: asphalt milling removes the top layer so the new surface finishes at the right height and bonds to a clean base.
An overlay only lasts if the base holds. Soft or failed areas are cut out and patched first, and cracks are dealt with so they do not show through. When the base has failed across a whole lot, full depth reclamation rebuilds it in place instead.
