The cement board should be set in Thinset, adjusting the thickness of the
Thinset mix to level the board. 1/4" board is a little thin if the floor is
not perfectly flat with enough firmness.

wrote in message
ups.com...
Im in the process of gutting a tiny half bath and Im about to tile the
floor. After pulling up the original flooring and cleaning it, I did a
quick dry layout of some of the tiles and noticed that a few spots in
the floor were not 100% level. At this point I put down 1/4 inch
backerboard to try an dlevel the floor. Unfortunately the problem is
still there. Can I get away with going a little heavy with the thinset
in the uneven areas? I know there are self leveling compounds, but I'd
like to avoid that if possible.