There isn't anything in the codebook regarding the construction of porches and their roofs, technically engineering required. This is how one jurisdiction has worked around that, their own prescriptive guidelines. Good pics and tables, adjustment may be needed for heavier snow or wind ;)
http://www.ci.bremerton.wa.us/forms/communitydev/permits/PorchCarport.pdf
http://www.ci.bremerton.wa.us/forms/communitydev/permits/residentialcarporthandout.pdf
That's good info to have reference to.
I'll just have to remember where it is parked. :-\