Shower Construction

I recommend the creation of a one-piece full on waterproof membrane for your shower all the way from the ceiling to the floor, including the floor (if you’re not using a one-piece fiberglass pan) and carefully tieing everything into your drain. Water is the big destroyer of tiny houses. First from leaks in the roof and exterior shell. Second from the water in your breath (condensation). Third from leaks in your shower and piping. Use a product specifically created for this purpose and remember any mechanical attachment through the membrane is a source of a leak. I recommend a one-piece fiberglass shower. Second, fiberglass or plastic panels glued to the membrane (no mechanical attachments) using special waterproof corner moldings. Third (heavy) a conventional tile surround with tile glued to waterproof backer board glued to your membrane (no mechanical attachments). This is a big, tricky job. Ask for help. Get a subcontractor who specializes in this. Especially with the movement of your TH, the corners of your shower will be stressed and could create cracked by the movement.