2,200 sq ft sloped driveway on a 14% grade

The Story

Why slopes need different engineering

This Sandia Heights property runs up a 14% grade from the street to the garage — steep enough that the previous driveway had developed visible slip lines where the asphalt was literally moving downhill under its own weight every summer.

Standard residential mix isn't designed for that. On a slope, the hot-mix needs to be stiffer (higher binder content, finer aggregate gradation) so it doesn't deform under gravity and heat. The rolling pass count also has to increase, and we lay the asphalt in two thinner lifts instead of one thick one — better compaction control on grade.

Engineering choices

• Tear-out of 2,200 sq ft of slip-line failed asphalt
• 5" compacted aggregate base over decomposed granite native
• 2 × 1.5" lifts of stiff-mix hot asphalt (3" total compacted)
• Custom drainage swale at the high point to direct monsoon water around the slab
• Saw-cut transition at the street curb for clean elevation match
• Extra rolling passes (8 vs typical 5) for grade compaction
• Written workmanship warranty