I just bought a home and want to put ceramic tiles in one of the rooms. I pulled up the rug and along with that came a layer of old hard tiles. Under the tiles is a concrete floor in good shape with some black glue left over from the tiles. Can I just put down thinset and tiles or do I need Ditra or Red Guard first. The floor is straight and in good shape. The only thing about the floor that I would have to prep is removing the black glue and if necessary fill in some tiny holes which are from those wooden brads when the carpet was installed.
Those old tiles were probably asphalt or vinyl asbestos tiles. Both of these types of tiles contain asbestos, and chances are that black "cut-back" adhesive contains asbestos too. When do think they were installed, when was the house built?
The recommended procedure is to cut as much as that adhesive off with a razor tool called a wallpaper scrapper, then when only a film remains, you can bond tiles or a membrane such as Ditra to it. The scrapper looks like this; http://www.core-industrial.com/manag...28Small%29.jpg Do not use solvents to remove the adhesive.
Be sure the "modified" thin set mortar says it's compatible with the cut-back. If the floor is small and has no cracks, you could skip the Ditra, but it is best to use it, or a similar product from Noble. Makes for better sleeping.
TILE GUY - retired- TROY, MI - Method & Product suitability consulting.
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