Won't work. You need to do a complete tearout and rebuild.

Thanks Sophie! I'm curious though why installing ceramic tile over tile is ok but not the river rock tiles?

People tile over tile in room floors, but I've never heard anybody try it in a shower. You've seen that application? The seals need to be SO much better...

These guys tile for a living and can probably give you the best answers - http://www.johnbridge.com/vbulletin

I would think, as long as the existing tile and base is in really good shape and still water tight, that the biggest obstacle would be getting a really good bond with the rocks to the tile. The other consideration would be the drain- you'd either have to raise it up or be content to have it sunken below the level of the new floor. If you can deal with those two things you may be able to do it, but I'm no expert - so ask the tile guys!

Your current should floor is sloped/prepared for the small tile we see in the photo. Applying a new surface to a sloped surface (for a different product) probably won't work...because you will change all the dynamics of this surface.

And tile over tile is a REALLY good way to waste money on more work with more stone. If you like the stone, then respect the stone. To get this to sit properly, the stone needs its own form of bed/slope/setting to get it right. The tile that is there is not going to be able to deal with it. It will HINDER the proper application.

If you were doing this from "scratch" would you allow an install (knowingly, with your eyes open and fingers crossed) that HINDERED the floor from functioning? Would you tell a tile setter to just "go ahead" even though they said, "Please. This isn't the best way to do it. There is a problem that I need to fix. If I don't fix it this will have to be redone very soon." Would you move forward with that scenario in ANY OTHER SETTING???

Play the "What if?" game. What if we are right and that a stone-over-tile install is a COMPLETE redo? Are you willing to pay 2.5 TIMES THE amount this should cost? Is that something that you are willing to risk?

If you are OK with paying 2.5 TIMES the "real" amount to do this properly (remove the tile, reset the slope/pan and then install the stone...and possibly rework the wall tile) then feel free to go ahead with the "stone over tile" option. If you can handle the extra time and the extra money, you are welcome to give it a try. But it is NOT something a well paid, well trained tile setter will be happy to do. The BEST professionals will get you to sign a waiver stating that you are knowingly entering into a high-risk install and that you have been advised against it by the professional. Once you sign the waiver, the tile setter will get to work. And that is the type of tile setter you want to hire when this needs to be redone.