I'm designing a pergola for my house and could use some insight on the size of beams required for safety and to eliminate sag. I'm planning to use 2x6 rafters spaced 16" OC. Due to the size of the existing concrete patio the 6X6 posts will be 14' apart on the long sides, and 8'on the other sides. What size beam do I need to span the 14' posts. Can I use 2 2X10's, each one bolted to the side of the posts? Would it be better to sandwich the two 2x's together then set it on top of the notched posts?
Thanks.