G Mulcaster wrote:
On Thu, 20 May 2010 10:18:54 -0700 (PDT), 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.

I've replaced my entrance grout twice.

The floor is a 9' span of 2 x 10s with two layers of plywood glued and
screwed together, totalling one inch thick. Ditra was placed on top
of that.

The sources I've read said you need a MINIMUM of 1 1/4" of wood under the
concrete board and tile on floors.