Double Ceiling Joist
I spent 8 months in MS after Hurricanes Katrina and Rita inspecting damaged homes. Back then, there was no building code for most of MS, and the one they had was rarely enforced. Net result, half the houses I inspected had been destroyed down to the foundations.
Fast forward to the present, there is a building code. You are supposed to get a permit. Your local code enforcement official will help you to understand what the requirements are for the particular type of structure you are building. You need to consider critical design issues such as hurricane clips for the rafters, plywood bracing for the frame, adequacy of bolts for the foundation. The span tables are just the start. I suggest you purchase a copy of the building code, review your plans for the project against the code, then talk to the building official about specifics for your local area.