Leader Home Centers - Free Deck Design SoftwareNow you can design your own deck with the new web-based Simpson Strong-Tie deck Design tool. It's easy and it's free! ( Be sure to read Helpful Hints below. ) The free Simpson Strong-Tie deck Planner software allows you to customize the size & shape of the deck, including adding multiple levels. Change the color and style of the decking, railing and support structure. Add walls, complete with windows and doors. You can even add patio furniture, potted plants or a barbeque grill.