Installing Composite Decking Over a Concrete Porch. In most decks, two-by-fours aren’t acceptable to use as joists. They’re too thin, too flexible, and leave you with a bouncy deck surface. You will have to pre-drill the holes in both the concrete and the boards.Click to see full answer. In this manner, can decking be laid on concrete?When you’re installing your wooden deck over this, the floor planks will not be installed directly over the concrete but rather on runners that are installed perpendicular to the house (so water drainage is not blocked).Additionally, can you lay Trex over existing deck? You will have no problem installing composite decking boards on the deck, as most composite decks have wood foundations. For several reasons, though, it’s important to remove the old deck planks first. Thereof, how do you attach deck boards to concrete? Use a wood bit to drill ½” pilot holes through the ledger board. Next, use a concrete bit to drill into the concrete wall. Install two bolts at the end of each ledger board. Hammer the sleeve anchor through the ledger board into the concrete wall.How do you prepare the ground under a deck? Preparing Deck Site Checklist Layout the shape of the deck with a hose or string and remove any sod. Ensure there are no underground services in the area where you will be digging. Locate the positions of the piers and footings. Dig the holes for the footings and piers. Prepare the soil with landscaping fabric.