BEFORE you rip out the old tile consider whether it wouldn't be easier to tile over the old. So long as the old tile is firmly fastened AND, probably more important, the added tile doesn't raise the floor above the threshold, you can tile over the old tile. I've done both (tiled over the old and ripped out) and they were equally good jobs. If you go for the rip out be ready for some heavy duty work. Good Luck