How to join seams between hardiebacker and drywall in a corner?

Question

I'm tackling a full bathroom drywall install for the first time and trying to make sure I don't make any unfixable mistakes. I am at the taping/mudding stage.

Based on my understanding, I can use paper tape and joint compound to do Seam 1, and I can use alkali-resistant fibatape and thinset mortar to do Seam 4.

The plan is to tile above the shower head, but not all the way to the ceiling (the upper most foot of hardiebacker and the ceiling we will paint).

1. For Seam 3 I plan on attaching a corner bead - do I then use thinset mortar on both the hardiebacker and drywall sides of the bead?
2. What about Seam 2? My guess is alkali-resistant fibatape and thinset mortar are what I need, but am I going to run into trouble trying to do that in a corner?
3. Does caulk or anything else need to go anywhere in these seams?

Thank you very much.

Answer 1

Don't worry as much about the drywall mud.

As you said, fibatape #4. Do that first. For #3, set your bead in drywall mud. Then, finish the drywall side in drywall mud and the upper side above the showerhead in drywall mud. Feather the lower portion of the bead out with thinset, just to keep everything on plane. Personally, I like to also paper tape the bead to the drywall in moist areas to prevent cracking later. That is not a requirement though, just a personal preference.

Seam #1 &#2 just finish with drywall mud & paper tape.

Looks good man, keep pushing forward.

Answer 2

Seam 2 doesn't need much where it's behind the tiles. I'd use fibatape and the tile adhesive will grab it (you'll get a squarer corner too). Use mud over the fibatape where it's above the tiles and will be painted.