First let me thank those in the plumbing forum (Mark thank you) for the good advise proffered. Though they have added to my work, I know it's the right thing to do.

So here's my situation -
- Upstairs bathroom in a 1930's duplex
- will be demoing an old tile floor to replace lead closet line with pvc to cast iron sewer line in wall
- when old tile removed will have 2" from tg subfloor to grade
- being an older building, floor declines 1" over 10' from door to exterior wall

Here's what I was thinking of doing once demo & plumbing are done.
- lay down overlapping roofing tar paper over tg as vapor barrier
- glue & screw 3/4" ply (bc grade) over subfloor
- pour self-leveling concrete to bring closer to level (deepest point would be 1" feathered to 1/4"
- glue & screw 1/4" hardiboard on top of this
- set terrazo tile with thin set

What do you think?

All advice or comments appreciated!

Thanks.

Since floor leveling that thick will require the use lath to prevent cracking, my approch would be a little different.
I would build up the lowest end with as much 3/4 plywood as I could, not coming above 1/8" below a level line of the highest point. Then switch to 1/2 plywood, then to 1/4" plywood,

Then pour the self leveling cement. That way the maximum depth of the self leveling would be 1/4".

I agree w/ harold.. this works well.
I used a piece of wood instead of a line but that's what I had.good luck