This was a conversion from an over-sized tub. This gave us ample room to bump "into" the shower area without taking too much away from the new shower's footprint. Once the tub/shower was taken down to the original studs we just built a new short wall (sometimes called a "pony wall"), tied back to the original back wall of the shower for support. Once framed, the entire shower is covered with 1/2" cement board and then finished as a "normal" tile job. The resulting "shelf" affect is 3 1/2" (the width of the 2x4 stud) + 1/2" cement board + another 1/2" (more or less) of tile and thin-set leaving the overall shelf being almost 5" deep....perfect for most shampoo bottles, etc. IF you aren't able to start with an over-sized tub you would have to steal that 5" from somewhere else (go into the back wall, move the shower out, or reduce the depth of the shower overall). I hope this answers your question.

Thank you for your response. Remodel starting soon. Will have a 12" rain shower head from ceiling centered to 36" half wall. Ledge will be at end where shower head hidden behind half walli with granite finishing off top of shelf. Hope all goes well and shelf doesn't get to wet! Yikes! I am a little scared.

Sounds like a great project. Just 2 quick comments: 1. Be sure to understand that most rain shower heads use only gravity to "drop" water down, which is unlike a regular shower head that uses water pressure to "spray" water out. The difference is sometime barely noticeable and some people do not mind at all, but some do. It might even appear that it was installed wrong or that the head wasn't working right because the "water pressure" was so different. SO just be aware there is a difference if you haven't used a rain head before.

2. I would suggest putting the granite ledge piece on with just a slight slant to it so that water will drain, if only a little, in the direction you want it to go. It doesn't have to be very much at all... less that 5 degrees off level is fine.... just to prevent water from sitting there or even worse - rolling back to the wall or outside.

Best of luck to you on your project.