
If your longest 2x4 doesn't span the entire distance, don’t worry. Add a second one starting from the other corner and run it back alongside the first, nailing it to at least two of the same joists. Have a helper hold the 2x4 in place while you drive the first nails. Driving 16d galvanized nails upward will give your hammer arm a workout!
Photo 1. Cut and nail a treated 2x4 diagonally from corner to corner under your deck. Drive two 16d galvanized nails at each joist.
