How to Build a Deck (with 120+ Pics, Diagrams, Pro-Tips, & Helpful . May 25, 2016 . Ground-contact lumber has .40 pounds of preservative per cubic foot, and above-ground rated lumber has .25 pounds. Pro-Tip: The size of posts .. Since the deck was 24 long, the band board consisted of two 2 x 8s butted against each other, and the transition at the double joist. Save. Using a string..