How far span can WRC 2x6 be placed as a pergola rafter/roof? Would be using 5 posts 6x6, 3 in front and 2 at back (connecting to an existing pergola), 4 beams 2x10x18, and need to know if the 2x6 can span over a 13 ft space with no additional support in the middle. These will over hang by 1.5 feet on each side making the 2x6 total length of 16ft. And will have 2x2 on top.
Simpson Strong-Tie just created a pergola designer software last week. You can access it by creating an account at the link below.
Use this as a tool to check your framing sizes and spacing. If you can't select the member size you want, it's because that member size is not strong enough for the spans that you've specified.
It also shows you the connections you need and gives you a detailed report of all the material quantities you need. This is a perfect step to take before your trip to the hardware store.