Expert: Dave Coil - 5/17/2004

Question
Dave,
10 months ago we had ceramic tile installed.  The grout started to break up within a week or two.  The installer said it is due to movement in our home, (although an engineer & building contractors disagree.)
He used 1/4" thick fiber board (approved for ceramic tile) & 1" nails placed 6-8" apart. He did tape the seams, did NOT use a flexible grout. Floor joists are the appropriate 16" apart.
Do you have any idea why the grout broke? Can it be fixed?  How could this have been prevented?
Thanks for your time.
Laurie

Answer
It sounds like he started correctly...one exception....Did they glue the 1/4" fiber board to the subfloor.  The nails are a good thing (a bit short) but the fiber board has to be bonded to the subfloor not just fastened.  A  tile mastic or thinset should have been placed before the fiberboard to give each additional strength.  The grout may have been too wet or too dry during the application and cause shrinkage.  You can easily add more grout if you need to.  You may need to chip some of the old out to give more bonding area.