Here's my problem...I am in the beginning stages if designing and building a patio cover over a concrete slab off the back of my garage. The slab has two support walls (in the shape of an L) that I plan on attaching ledger boards to. the rest of the patio will be open to the yard just using 4x4 posts. The design calls for TWO 2x6 pressure treated ceiling joists (running parallel) 3.5 inches apart, big space, then another two 2x6's , a big space, etc.. My question is...How far apart can I legally place the joists apart from each other? I know if it was just one 2x6 I could place them every 24''o/c, but if it's (2) 2x6's, can I legally place them 48o/c? Any feedback is appreciated. And thank you ahead of time.