Have a shower with wall tiles from floor to ceiling. The wall tiles are
fine, the floor tiles I like to replace. I don't want to damage the shower
pan underneath, so is it possible to lay new tiles on top of the existing
tiles (which seems to be solid). If so, do I need to apply some sort of
impervious layer first before laying second layer? Do I need to use some
special thinset? The existing tiles are small, 1"x1" ceramic tiles, I would
like to replace with even smaller stone mosiac tiles (the ones you buy that
comes in a 12x12 sheet).

The other question will be the shower drain. The new tiles will raise the
floor level in the shower which is not a problem - the curb is 8" tall now.
But the drain will be lower than the floor. Should I raise the drain (if so
how?) or do something else?

Thanks,

O