"My ceramic tile floor crunches when I walk on it" or "My grout is falling out of my bathroom tiles and my house is only two years old". I get this call at least once a month and unfortunately the answer almost always is, "You need a new floor" or "you need to replace your wall tile". The most common cause is improper substraight, underlayment or wrong type and not enough thinset. Please look at the photos at the bottom of the page showing the replacement of a white tile bathroom with beautiful saturnia tile.
This was a case where the builder set the tile on a wooden substraight with wall mastic. Once the wood gets wet it swells up and the bond is broken. A proper floor should be set on concrete or if on a wood subfloor a proper underlayment such as Durock or Ditra.