The walls were constructed out of 1/8" plywood. Painted about 8 inches up the backside with liquid rubber. Then screwed to the walls with sika. Then the seams were sealed with foundation tape and everything painted over twice with liquid rubber. USA rubber sells a non-solvent liquid rubber. I think I was the firs to use it to creat a shower...typically used to create waterproof foundations and swimming Pool liners. The light blue "paint" you see in the shelving..that is liquid rubber. I liked the color so much I kept it just rubber on the ceiling and inside this shelf unit
The finish is just elcheapo vinyl tile. The glue on the back of those "self stick" tiles does not hold on rubber (lesson I learned the hard way on th rubber backsplash in the galley). So..I used Fuze painted unto the backs then installed them. The trim is all pvc with latex caulking.
The shower pan is just a poly resin poured onto the plywood floor...over blue crushed poly stone, and the finish created by roughing up the surface and including a sprinkle of more polystone dust before it cured. The frame was created by gluing in thin strips of plastic..about 3 inches up the wall. Since the wall board would cover it .. it didn't matter what color..I used white cause it was cheap. Be sure to place a shower drain into the hole sticking up higher than your pour. I watched several YouTube posts of various methods...and material to get different looks. I wanted something very light weight, but the guy that did this over real stone pebbles was very tempting to copy. Poly resin can be bought at any hardware store.