I'm building a 5'x7" shower with a bench across the backside, opposite the door. Will fasten two 4x4 posts to the house and set the others in stone dust, also using 3 rows of 2x4's completing the frame. Then I wil use withewr mahagony or Pt decking for the sides.
Not sure what I am going to do for the floor, I might just do a slightly elevated Mahagony above stone dust and pee stone that is pitched away to an area of Stone that is close by.