Here is a picture of a typical bench I install in most of my showers if there is enough room. I do not frame these out of wood, rather I run the shedule 40 CPE pan liner up the wall 2' and build it out of CMU block and float over it and set tile over that. This provides a much stronger bench without the chance of leakage. As you can see the the two matching glass block windows in the shower. I also will put these in upon request.