How deep should gravel be? Compacted base depth by use — walk, driveway, street

Gravel depth is not one number — it climbs with the load. ICPI Tech Spec 2: 4–6″ of compacted aggregate base under walks, 6–8″ under driveways, 8–12″ under streets; decorative cover is 2–3″. Foundation drainage (IRC R405.1) uses ≥4″ of open-graded #57.

What this diagram shows

Four gravel-filled columns of increasing height on a common ground line, showing the compacted depth each job needs. Decorative cover over landscape fabric is only 2 to 3 inches. A paver base under a walkway is 4 to 6 inches, a driveway base is 6 to 8 inches, and a street or heavy-traffic base is 8 to 12 inches, per ICPI Tech Spec 2. Foundation drainage wants at least 4 inches of clean open-graded #57 stone around footing drains per IRC R405.1. The calculator runs its tonnage on the compacted depth, so the depth is chosen from the job before the yards are computed.