The deck is 16'x16'. I want to build the porch the full 16' width of the deck and to a partial depth of 10', leaving a 6' deep section of the deck open to the sky. The 16' width will tie into the existing house wall and roof and there is a sliding glass door centered in that wall.
I plan to support the outer corners with 4x4 posts (properly fastened to the deck), frame the porch roof with 10' 2x4s rafters and finish the roof with galvanized sheet metal roofing. There will be a 2x6 (??) 16'long (!!) footer "beam" between the 4x4 posts at 8' from the house wall (2' of overhang on the metal roofing).
I would like to have that 16' "beam" free and open in the middle, but I'm not sure if it can support a 16' span of the porch roof without sagging (Alabama, so snow loads are minimal). If it can't, I'll put in a 4x4 post at mid-span and live with it.
I don't want to get into buying bigger "timbers" 6x6s or whatever or steel beams; I want to keep it rustic. And I want the metal roof because I like the sound of rain on a metal roof.