The design is based on typical Japanese design aesthetics of placing the toilet in a separate space away from the bathing area and also having a separate changing room. In my design the changing room has storage for towels and toiletries, a basket for clothes, a place to hang your robe and a sink.
That leaves the bathing room with tub and shower that is entered via the shower door.
This addition began with tearing down the original bathroom addition that was poorly insulated, had aluminum wiring, water damaged sub floor soft enough to put your foot through and termite damage.
I rebuilt on the existing foundation framing with 2x4 pressure treated lumber for the bottom plate and also studs to resist future water and termite damage. I cantilevered the roof 4'-6" beyond the wall with 2x6 studs to offer shade over a small walk out deck, then insulated with r-19 batt and Reflectix foil insulation for a combined r-30 Link Here.
Exterior is T 111 exterior grade sheathing protected with wood stain.
Insulation in walls are standard r-13 batt insulation covered with 5/8" drywall. crawlspace was completely insulated using Reflectix foil insulation, then double 6 ml plastic over the dirt crawlspace.