i am planning on adding an addition onto my garage. it is a 20x40 gable roof garage. first off how would i go about adding a lean to style addition on the side. it looks like an 8 pitch roof and i would like to make the addition probably a 2 pitch. extended out about 10/12 feet. should i somehow add rafters beneath the soffit since i want to put a metal roof on it or should i tear up some of the roof and add trusses? could anyone give me some ideas on what i should do and then what to do after the fact?