So, when it comes to how the boards of your deck should run (parallel or perpendicular) they can really go either way! It all depends on where the joists and girders are placed and where the deck is built. Girders, aka beams, is a board or composite of boards that support the structure of the deck. Joists support the decking itself. If your unsure which is the best option and are ready to build your dream deck call MAW Construction, Inc. for a free consultation.