We are in the process of having a garden room built however, the builder has decided to jump ship and left us with a half finished build so we have decided to try and finish what we can ourselves. We are currently trying to make the building water tight. There is no overhang to the roof but we would like one. How do we go about making an overhang as there are no protruding roof joists. We are planning on doing a felt roof. Any advice greatly appreciated!