Carport engineering

I am extending a gable end of a roof, not changing the original footprint. I'm only changing the roof line of the structure. Pre-existing the back of the house had a flat roof that was over an addition to the house. Building code inspectors say that I need to have an engineer for the part that is where the carport is. We have already started constructing the carport area. We set and concreted 8x8 cedar post in the ground 2' foot deep.