I have a attach garage with about a 2.5 foot step from the house to the garage surface. I want to build a room directly from the door(same height). I want to know if I can build a wall then attach joist hangers to the wall and to the house. The room width is approximately 6 feet by 20feet using 2 x 8 for the joist 16 on center with 3/4 ' for the floor.