Asphalt driveway layer stack — subgrade, aggregate base, and HMA courses in cross-section
A driveway is a layer stack, not a slab: compacted subgrade → ~6″ crushed-stone base → tack coat → 2.5–3″ of hot-mix asphalt. The base carries the load — NAPA rates 1″ of HMA ≈ 3″ of aggregate base.
What this diagram shows
A cut section of a residential asphalt driveway showing the layer stack from the bottom up: a compacted subgrade, an optional woven geotextile fabric over soft or clay soil, about six inches of compacted dense-graded aggregate base (crusher run), a thin tack coat that bonds the lifts, an optional binder course of hot-mix asphalt, and the surface course of hot-mix asphalt that you drive on. The aggregate base does most of the structural work, and one inch of asphalt is structurally worth about three inches of aggregate base, which is why the base is the thickest layer.
Asphalt Driveway Calculator
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