I am designing an awning roof to protect some exterior french doors on the west side of my home. The roof will be a simple shed style, and will extend 7 ft from the house with a 3:12 pitch and two supports will be 14 ft apart (a 15 ft wide roof). I intend to use standing seam copper or aluminum as the finsih material. Do you have a reference that I might access online that will help me with calculating the header dimensions? How complex of a calculation is this? Thanks.