I'm building a simple lean-to porch, and need to figure out the specs for sizing and spacing the rafters, and the beams that the rafters will sit on, given a specific span. Also, I would like it to have the minimum pitch while using asphalt shingles. Any tips on a good online resource to figure these things out? The footprint will be 8' x 16".
2x6 rafters 16" on center 4/12 pitch, beam will be dependent on post spacing rule of thumb 1" of beam/header for 1' of span.
Love it, thank you, IP. For the beam, can I go big enough with dimensional lumber to span the full 16' with two posts? Maybe a lamination of 2 or 3 2x8 or 2x10's approximately 14' apart with 16" overhang on both ends? If not, using 3 posts, would a 4x6 beam be sufficient?
use the same material as the post and you can bolt it between the headers and lag to the upright post.
You really need the tables for lumber species/grade dimension pitch/spacing/length for your live loads and then multipliers for dead loads A slate roof will not exist in the same place in the live load tables as a tin roof. Nor will the snow loads in northern Maine exist in the same place in the tables as Delaware. just google live load and dead load tables rafter table spans - you'll find what you need to at least be close.
