"Tony" wrote in message
...

you cannot flatten a floor with hardibacker, as it is flexible and will
conform to the floor that already exists when you lay it down. you need a
product that is non-flexible or will conform to the floor unevenness on
one
side, but will remain flat on the other side. the ways to do that are to
either rip up the entire floor down to the joists and build it up again
shimming the floor to make it flat, or put a moldable material on top to
make it flat. THAT is what we've been trying to tell you.


I wasnt asking if I can flatten the floor with hardibacker. I was asking
if there was a way to put
something under the hardibacker board (like thinset) that would make a
flat surface under it. So, I
have a choice of mud or rip up the floor and put another down. I am
assuming that the higher part of
the floor is where the joist is. Couldnt I take that one piece of plywood
out and plane it down a
bit. The rise is only in one section of the floor that seems to be where
the joist is. Please excuse
my ignorance about this. I am a computer consultant, not a builder. I have
learned a lot since
buying this house 3 years ago and this is an area I have never dabbled in.

Tony

i am a computer consultant too, for about 40 years, however, i know where my
library card is and am not afraid to use it. you may find that reading a
book on tiling may help you better than continually asking the same question
over and over.

no, you cannot plane down plywood. no, you do not need mud. there are, or
should be, multiple joists under your floor. yes, you have to level the
floor. yes, you have to use a cement type of product to do so. yes, there is
a product you can put under the hardibacker to make it level. that is the
cement type of product that we all have referred to. no, it is not mud. a
mud floor would typically be approximately 1.5" of cement, screed out to be
both flat and level. you only need a very thin layer of screed material,
only enough to fill in the low spots. you would then put the hardibacker on
top of that hardened material.