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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.

  • They make both inside and outside corners. I have used several different brands with plastic and metal behind the tape. I find the metal to hold up the best the plastic type tends to crack. I have not had any rusting issues with the metal on the ones I have done but have found some that were a bit rusty on demo before remodels..
    – Ed Beal
    Commented Aug 31, 2017 at 21:57
  • Just wondering if after you put up the hardie backer if you are going to water proof the wall. I know some don't, but are you going to?
    – Sally
    Commented Sep 1, 2017 at 19:19
  • @Sally I was not planning on it. I know people have mixed opinions about this. The Hardie Backer instructions (jameshardie.com/d2w/installation/hardiebacker-us-en.pdf) do not mention needing any water proofing/vapor barriers/etc... so I am not planning on adding any. Commented Sep 1, 2017 at 20:34
  • Hardibacker is kind of waterproof, so I don't see what is to be gained. Might even reduce the carrying capacity of the Hardibacker as then the bond is only as good as the bond between the waterproofing agent and the board...
    – handyman
    Commented Sep 5, 2017 at 17:41

2 Answers 2


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.


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.

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