I failed to fully explain the idea, which is indeed on the crazy side. If the user does need a ten foot tall or so roof he or she could dig and on the outside of the perimeter place a pipe with holes on the bottom covered with a synthetic permeable fabric. Then using the grade in the lot install a drain pipe to move the water away from the area where the shed is installed. It would be an expensive alternative but at least the user would have the needed head room.