Looking to convert flat roof garage to usuable room, size is bout 10 x 12 foot. Needs walls/ceilings drylined, already has electricity, needs new door entrance knocked through from hallway, garage door removed and wall built up for new window and new flooring. Also what would my option be re: roof, tcurrently the flat roof extends to the back extension so dont know what the options would be for adding some sort of a roof. Anyone have any ideas how much garage conversion would cost?