See my post in "house remodel". I replaced our broken, leaking escape hatch this fall and there have been ZERO leaks through the winter. Remove the ceiling, cut away some insulation, install some new framing to accommodate the larger size and install the hatch. I'll see if I can get the photos I have posted. I'm better with hand & power tools than I am with a computer. I'm willing to bet that most of the old framing around where the old hatch is will be rotted.