On May 20, 6:18�pm, KOS wrote:
hi, i had a bathroom done 2 years ago, new floor with new tiles... I
had to get the tileman over to repair some grout that was coming
out... only 2 years later???!! �why does this happen? I have older
bathrooms where the floor was done 20 years ago and grout is not
coming out.

Well there are two possibilites. One is that the substrate is flexing
excessively. If the ply is not down tight to all the joists (ie the
joist are not lined up you might have a problem. You didn't say how
far apart your joists were, (the other factor in the equation).
However the most likely is that the wrong tile adhesive and/or grout
has been used. A speacial more expensive one is need to fix tiles to
timber. Also a special grout. As long as the tiles are not coming
loose I would remove all the grout and put in silicone caulk instead.