3rd floor for porch roof?

[Reiter]

I have been struggling with the correct way to get this vaulted gable roof over a porch which cuts into the house by 6 feet. After learning about creating the zero floor just for the foundation only I decided to take the same approach with this porch roof. I have made it to the point where I was ready to start trimming and have found that I cannot see the roof planes at the same time so placing intersection points can be done. I can see 3rd floor I created just for the roof with 18" walls and no floors with room dividers for walls so I could build the raised gable on a room of its own. here's the plan and a few screen shots of what I'm seeing. I know this may be a strange way to build this, but my desperate inexperience has me grasping as anything to try and discover a way to get this done. 

covered porch.zip