I know this has been discussed her before with different responses, but I'm not sure how treat the seam between backer board (cement board) and green board in a shower area. I realize this is a specific and rather picky question.
Rather than make the seam exactly on the tile edge, my first theory is that the tile should slightly overlap onto the greenboard, maybe an inch or less.
I should use fiberglass tape and I should use the seam side of the greenboard. In other words, the side that's indented to allow for the tape.
Questions:
- Should I try my best to squeeze thinset INTO the seam? I'm not sure if the argument is to have a good seal or if there would be some need for expansion between differnent materials.
- What do I mud with? On the BB side I'll go with the thinset, but do I also use thinset on the Green board side? Thinset, to my understanding, dries to a hard fine grain hard cement surface. How am I supposed to sand that down and get a nice smooth surface that will accept paint? Is the idea to put drywall joint compond on top of the dried thinset and then sand that flush? Will the indented portion be deep enough to allow this? This is my main question and it's been answered in different ways, so if you're kind enough to offer me some advice, please back it up with as much justification as you can.
- If the tile overlaps the greenboard seam slightly and if I'm using the indented side of the greenboard, then maybe I could intentionally leave a slightly gap between the tile bottom and the greenboard and fill that gap with caulking? Or is that just making it harder than it needs to be?
Thanks for your help!