Each time you add plywood sheathing to a side wall and when you install the front 2x6â??s, the structure will get stiffer and stiffer. At each step you need to check to make sure that the side-walls are perpendicular to the back wall. This structure will not completely immovable, in respect to remaining square, until the floor and ceiling are installed. However, it does get damn hard to move so be sure to frequently check to make sure the structure is square and plumb.

The floor and ceiling joists are installed. I put a slight (1/2â?) drop in the floor so that the water will flow to the drain. The No. 8 photo below shows the framing where the ceiling will be attached. Note the 2x4 that is laying flat. This is called â??backingâ?. When you are done with the structural framing for the floor and ceiling, you need to look where the floor/ceiling plywood will be attached and make sure that there is wood backing for the floor/ceiling plywood to attach to, that there is wood under the edge of the plywood all the way around.