Your Place: Anchor Subfloor to Avoid Problems

(MCT)—Q: I live in a condo and recently had my carpet pulled up, plywood put down, and then tile on top in my master bath dressing room.

After six months, the grout in the upper area began to crumble and came out. The tile man came back and re-grouted the area. He does not know why it is happening; there was no water leakage.

Now it is happening again in the same area. The tile man has 25 years experience and came highly recommended.

Can you offer some advice?

A: I’d probably blame the plywood used as the underlayment. If it wasn’t properly anchored to the joists, there might be enough give in it that when you walk on it, the grout gets loosened, even if the tiles are in solid.

I put down exterior plywood once as underlayment for tile, but I used drywall screws to anchor it to the joists and the flooring underneath.

I prefer Durock or other kind of cement board as underlayment — again properly anchored.