Gambrel Roof over Two Different Sections of Wall in Q&A Posted January 26, 2016 You have the front and back walls set to Full Gable. Only the end walls should be marked as Full Gable. Fix that and the gambrel roof builds, although I'm guessing you will need to change some settings. Thanks. The full gable on the opposing walls was an artifact of switching roof direction. The one thing that I did not have done that is needed in HD Pro is the "Build Roof Planes" check box should be checked to get the refresh of the roof line. It is located in the roof dialogue box.