I'd like to install slate tiles over a pre-existing plywood floor. The plywood floor is 3/4" and sits on joists.
There's a dip about 3/8" deep by 2 feet wide by 5 feet long. My plan was to fill it with self-leveling compound, before installing the cement backerboard and then the tiles. However, the guys at the tile store seem oddly negative about using self-leveling compound. Is there any reason not to? If so, what are my alternatives?