I have been asked to build a clear polycarbonate gable roof over a patio. One end will extend over the bottom of an existing shingled gable roof and gutter. Normally I would simply build it free standing with posts, but the owner doesn't want posts close to the house (as they would be in the wrong place). Instead she wants that end of the roof to be supported by posts on the existing shingled pitched roof. I'm thinking I will have to attach them to the exterior wall and go up through the roof and then find a way to flash around them. They will be fairly well protected by the new roof, but I'm still a little concerned they may be hard to make watertight. Does anyone know of the best way to flash around the posts, or a better way to support the new roof that doesn't involve cutting in to the roof?