How to Build a Structural Deck Frame

D•eck building is the ultimate test of a homeowner's precision and patience. At its heart, the frame is the skeletal system of your outdoor space; if the posts, beams, and joists aren't square and level, no amount of quality decking will ever look right. You are managing forces—gravity, load, and moisture—that will test the integrity of your build for decades. A job done well results in a frame that doesn't bounce when you walk on it and stands perfectly plumb. You are creating a foundation that needs to resist rot and lateral movement. Take your time with the layout phase, as your perimeter dimensions are the map for every subsequent step. A deck that starts square stays square.

1. Protect the House First. Attach the ledger board to the house rim joist using structural lag screws or thru-bolts. Ensure it is perfectly level and properly flashed to prevent water from entering your house wall.
2. Dig Below the Frost Line. Measure the footing locations based on your design plan and dig to below your local frost line. Pour concrete into the tube forms and insert adjustable post bases while the concrete is still wet.
3. Plumb Posts Both Ways. Measure and cut your 6x6 pressure-treated posts to height. Install them into the post bases, check for plumb on two sides with a level, and secure them with galvanized fasteners.
4. Brace Before Bolting. Install the support beams across the top of your posts, either by resting them on the post tops or bolting them to the sides of the posts. Ensure the beam is flush with the tops of the post to provide a solid surface for joists.
5. Hangers First, Boards Second. Mark the joist spacing on the ledger board and the outer rim joist, typically 16 inches on center. Use heavy-duty metal joist hangers to secure each board to the ledger and the beam.
6. Square the Frame Now. Attach the outer rim joist to the ends of your joists to tie the frame together. Install mid-span blocking between joists to prevent them from twisting or warping over time.