On the back of the house that I'm putting a room addition onto I've got a hip roof. The contractor plans on over building the new roof (for the addition) above the old roof. Where the old / new roof meet there would be interlacing (every other shingle would come off so that the new roof will tie in to the existing roof hip. He says that a pass-through will be put in place to the roof over the main house (for access / electrical / etc.) Question to forum: Is this typically how a room addition is tied in to the main house? I was thinking all of the old roof (under the new roof) would be removed as it is no longer necessary and in my mind could only cause issues down the road (make access more difficult / harder to detect leaks in roof / etc.) Anyone have opinions on this?