Saturday: Prepare the bed, lay the bblestones, and grout (Steps 6–18). How to Build a bblestone Driveway Apron 1. Measure the Driveway Photo by Kolin Smith. A typical driveway apron extends 10 feet up from the street—in many places, smack in the public right-of . lightweight Ground protection mats 15mm thick for apron. Temporary Access Mats