I am replacing our wooden floor and installing tile. The plywood is 11/16", Backer Board is 1/4", the tile is 5/16", I will be using mastic between the wood and backer board and then using it for the Tile. Using a 1/4" Notched Trowel, how much height will be created by the mastic? The drain pipe is being replaced as well as the toilet flange so need to know the height from the floor joist to the bottom of the flange. The new drain will be P.V.C. so not sure how much give I will have once it is glued together. I was going to have the bottom of the flange at 1 3/8" above the floor joist. Will this be to high?

You're making a simple job way to complicated We simply install a elbo under the joist 11 1/2" from the finished wall to center, we then add a raiser from the elbo to a few inches above the tile floor. We then cut the raiser off flush with the floor and prime and glue on a flange. Sound like a plan? Tom

Tom, You made it so simple. Lol I wonder where my brain is or was. Thinking about finding 2" X 1 1/2" studs and rot. I really appreciate your simple solution.

I really appreciate your simple solution.
Hey! Simple guys give simple solutions. Good luck, Tom