QUESTION

Old Thin-set Removal - The first floor of my house is currently comprised of carpet in the living areas and tile in the kitchen and major hallways. I would like to install travertine through out the entire first floor. I've removed all the tile, but the thinset used to attatch the old tile is firmly attached to the concrete. The height difference between the thinset and the concrete foundation (after I removed the carpet) is negligible. Is it critical that I remove (scarify) all the adhering thinset on the floor prior to installing travertine? What is your recommended floor preparation under these circumstances? I want the foundation to be solid and the job to be done correctly, and would greatly appreciate your advice. My house is 12 years old and is located in the area of Phoenix, AZ. Thank you very much.

ANSWER

ANSWER - There is much to consider in preparation when installing stone or ceramic tile, and during the installation process.  I will only respond to your specific question, so my answer in itself will not ensure a successful installation.

It is a good sign that the thin-set adhesive from the old ceramic tile has bonded well to the concrete slab.  To achieve a nice flat surface for the travertine tile then the substrate needs to be relatively flat and consistent.  You can compensate for some irregularities in the concrete slab with the thin-set mortar, but it can be a problem if you use too much thin-set.  Too much thin-set is more expensive, it can cause excessive shrinkage that can lead to other problems, and it is more difficult to achieve an over all flat travertine surface.

I would recommend trying to remove as much of the thin-set as possible and then use an appropriate modified thin-set to skim over the rough surfaces to smooth it out and to achieve a flat surface.     Good Luck!