Asphalt Resurfacing and Overlays in Madison, WI

An overlay is a fresh layer of hot-mix asphalt tacked onto old pavement whose base is still sound, and it is the same treatment the City of Madison uses to stretch the life of its own streets. City Engineering rates every street every two years, lists those scoring 5 or lower on its 10-point scale for resurfacing, and mills or pulverizes the old surface before paving a new layer, about five miles of street a year, with the goal of putting off reconstruction for 30 years or more. A private driveway or lot works the same way. Resurface while the base holds and the new layer resets the clock; resurface over a failed base and the old cracks return through the new mat. Full replacement is the alternative when the base is gone.

The PASER rating scale, produced by the Transportation Information Center at UW-Madison and revised in 2013, gives a practical way to sort surfaces. A 6 shows slight raveling and traffic wear. A 5 shows moderate to severe raveling and calls for a preservative treatment such as a seal coat or an overlay. A 4 needs structural improvement, which in practice means an overlay, and a 3, with closely spaced cracking, needs a structural overlay at least 2 inches thick, which the manual says will benefit from milling and will very likely need patching first. At 2, with alligator cracking over 25 percent of the surface, the manual calls for reconstruction. Overlays belong in the 3-to-6 band.

Thickness creates the grade problem. WAPA's minimum lift is 1.25 inches for a 9.5-millimeter No. 5 mix and 1.75 inches for a 12.5-millimeter No. 4, so any overlay raises the surface by at least that much. On a driveway the extra height has to disappear somewhere: at the garage slab, where water must not run toward the door, and at the public sidewalk and apron, which belong to the right-of-way. Crews handle it by milling the old asphalt down along those edges so the new layer meets them flush, or by milling the whole surface where the drive has already been overlaid once.

Preparation is most of the result. Soft spots are saw-cut and replaced full depth first, because an overlay bridges nothing; cracks are cleaned and filled; the surface is swept; and a tack coat bonds the layers, which City specifications allow only when the air is 32 degrees or warmer. Cracks in the old pavement tend to reflect up through the new one, the reflection cracking the PASER manual describes along old joints, so a contractor should say how existing cracks will be treated. Asphalt repair covers the patching side.

Price is the main reason to choose resurfacing when it will work. Current national guides put an overlay at $3 to $7 per square foot against $8 to $15 for tear-out and replacement, and HomeGuide estimates that an overlay on a driveway in reasonable condition saves 20 to 30 percent compared with full replacement. The saving disappears if the overlay fails early over a weak base, which is why the base check comes before the price.

Season matters more for a thin layer than a thick one, because a thin lift holds its heat for less time and has to be compacted before it cools. City specifications set 40 degrees as the floor for placing upper-layer asphalt, and NOAA's October normal low at Dane County Regional Airport is 38.8 degrees, so late-season overlays are better booked for September than for the last weeks of October.