It depends on what your subfloor system is, whether slab or crawlspace. A crack isolation membrane is always a good idea on a slab, and for a crawlspace, you have to know your joist size, spacing, and the thickness of your subfloor to be able to calculate deflection. (Google deflectometer and enter in that information to see if your floors are stiff enough for natural stone.)

I'm on the third floor of a 3 story small condo building. I'm not familiar with what the sub-floor would be.