In the old days, a bathroom was called a water closet. Since the water facilities in my tiny home consist of a sink and shower, I use the term water closet instead of bathroom. First, I had to put up a 4x8 piece of masonite as the ceiling. This prop was the only way my uncle and I could get it to stay in one place to be bolted down.
Next came installing the shower pan. It turned out that I had misjudged the drain outlet and had to prop the pan up on bricks. Note the drain connector, which eventually had to be replaced.
My uncle had to remove the big gray Schedule 80 connector and clamp the drain outlet onto the pipe with this clamp-well, half of it anyway.
My uncle bolted together this wood platform for the sink pan from redwood, which is less susceptible to rot. I wound up using heavy duty epoxy glue to glue it to the bricks, then to glue to the bricks to the floor.
This is the shower pan in place. My uncle glued it on after he clamped the drain, and apparently he got it a little off. Whoops! Also, I misjudged the placement of the drain and it wound up a little too far from the back wall.
Getting up the wood walls for the shower was a challenge. We had to cut the back wall wood in half to get it aligned with the outlet pipes.