janebrain15 Thank you all for your comments. I'll check with the stone supplier. I am not doing this work myself. My contractor has not worked with a floating type granite bench before and I want to be sure that this is done correctly to prevent injury and costly mistakes . I read somewhere that a bench this heavy needs steel support and that the 2x4s are notched in so that the edges of the bench are not resting on the tile edges but rather in a U channel attached to the 2x4s.

Wow Great Place Absolutely the slab is NOT resting on the tile edges, that would be incredibly dangerous.
But whatever support was used, there is most definitely additional support, hidden from view.

ahoh HI. We found them at the Arizona tile store in their sample tile jobs they have installed around the place so you can actually see and feel them as they would be in your home. I asked the girl and those were the smoothest stones they had and when i took off my shoes to see how they felt even with my thick socks on my wife an i were glad we tried it in the store. we both thought while it looks neet that no way would we want them in our shower. I would really think twice unless you really have tough feet. just my 2 cents.

Pebble Tile Shop This is our #1 question we get about our tile. I know a lot of people love the feel of walking on pebble tile. I do! However we often get this question and so I say get a sample of both traditional and sliced pebble tile. The sliced give a flat walking surface with the beauty of pebble tile: http://www.pebbletileshop.com/products/Sliced-Tan-and-White-Pebble-Tile.html#
If you get a sample you can walk on both and feel the difference on your feet. Some people prefer a more 'flat' feel but still want the look of the pebble tile. Just an option to check out. Good luck on your project!