I'm building a 12' wide x 16' long storage bldg. My foundation is conventional and is 12x16. I want to put a 4' wide porch on the front ( the 12' side). I'm building a barn type roof and I want it to extend over the porch. How do I build my 16' walls to extend the support over the 4' porch? I'm going to use 4x4 post on the corners of the porch.