On May 2, 4:20*pm, "
wrote:
I am renovating a bathroom. The rooms is stripped to the studs with a
plywood base.

I plan to put a layer of cement board down over the plywood as a base
for the tilers to work on.

The plywood is rather uneven so the cement board will ride over
ridges.

Is there some kind of compound I should apply first to level out the
floor before the cement board or should I simply not be concerned?

The 'compound' you need is called a sander, either a belt sander or
(easier) random orbit sander. Given a typical 8 x 10 bathroom you can
get all the bumps out of the floor in about 15 minutes. Some pros then
coat the plywood with the cheapest polyurethane they can find to get
better adhesion/performance out of the thinset or whatever they use
under the tile substrate board. This method will yield the sturdiest
floor for unusually thin or even fragile tiles.. HTH

Joe