There's no real need in waterproofing the floor unless you expect to have huge amounts of water on it. If that was the case you really need a drain in the floor.

Two other points: 1) make sure your waterproofing goes up to the level of the shower head, and 2) make sure you plan on tile going above the joint where the CBU and drywall meet.

You may also want to consider a good quality paint for the walls and ceiling to prevent moisture from permeating into the drywall.

Thank you RC and Kman. Your advice is greatly appreciated!
(I couldn't access the forum earlier or would have replied sooner)
The reason I was thinking of putting Redgard on the floor is that my house is a ranch with a dormer added by the original owner. The bathrrom I'm working on is on this second floor.
There is insulation under the floor (which I assume was the previous attic).
I don't anticipate a lot of water, or even regular use of this shower, but just to try and keep moisture from permeating the cbu on the floor,(i.e.overflowing toilet?! OH GOD) I'm hoping the Redgard may help. I was told to use the Redgard and fiberglass cloth a few inches up the wall cbu to keep corners sealed.

Thanks again,
Bob

Hi Bob,

Since you're going to flash the walls with cloth and Redguard, you will get a benefit, just in case. But, how will you treat the doorway? Go ahead and do it anyway.

Jaz

That did cross my mind, and I think I'm going to use a granite or synthetic threshhold, that will create a step above the tile.

I need a transition from the bath to the adjoining hall because of the diff. in heights anyway, and if I put the threshhold on the Durock,I should have a 1/2 inch step after tiling.(Using a 3/4" threshhold)
If sealed,I'm hoping this will contain the water in the bathroom....unless it floods!!
I'm just kinda wingin' it...

Bob