I had to replace the flooring in my laundry room and installed new Advantech sub flooring. I used thin-set mortar and installed ceramic tile. After 4 days, I was getting ready to do the grout and I noticed the tiles were loose. Most of them were the first tile I laid. What did I do wrong?

 

Welcome to the forums! For ceramic tile, installation on wood floor is not acceptable. First, the wood will absorb the moisture from your thinset and cause it to dry too quickly. You always install a concrete backer underlayment (cbu) in a bed of thinset, screwing it as prescribed by the manufacturer, then thinsetting your tiles to that. It gives a more stable environment for the tile to lay. However, all is not lost. If your tile are coming loose, you may can salvage them (doubtful), lay down cbu (I prefer 1/4" hardiebacker) and start over. Don't have your thinset too wet, and use a 1/4 x 1/4 notched trowel.

 

Yep, what Larry said.

There are no thinsets that can be used to set tile over osb. Additionally, you always need an underlayment with ceramic tile.

 

Just happen to see this conversation - Q. Does the same need for underlayment also pertain to ceramic tile installed on a ground floor concrete slab?? Planning on taking up the carpet and replacing with natural stone tile.

Thanks -

 

Tile directly on concrete is fine if the concrete is in good shape, level, smooth and free of sealers (like paint) and glues which would inhibit adhesion of the thinset

 

Hi feem,

Please tell us how it is that you thought is was OK to install tile direct to OSB. Did someone at the lumber department tell you, or did you not bother to read the directions on the bag of thin set? Did you use thin set? Tell us more to try to help others.

Jaz