You will not find 9/16” steel form deck in 20 gauge. The heaviest gauge available for this deck profile is 22 gauge as shown in the first table below. The three tables below provide you with the available gauges for all steel Steel Form Deck, Steel Roof Deck, and Composite Steel Deck profiles. Remember that as gauge numbers decrease, the material thickness increases. (ex. 18 gauge is thicker than 20 gauge) The Steel Deck Experts at D-MAC know every steel deck profile and gauge available. If you have any questions regarding steel deck please give us a call at (888) 731-7368.