TomYoung wrote:
Hi all:

I just finished installing cement backer board around my tub. In just
about every spot I got (more or less) the required 1/8" gap between
board edges. However, in one corner where a horizontal sheet (3'
edge) meets the adjacent sheet the gap runs from just about 0" at the
top to about 3/8" at the bottom of the sheet. This is the top sheet
of backer board on the corner adjacent to the shower head so I'm not
too worried about the 0" clearance - very little water will ever hit
this spot - but more concerned about the 3/8" gap at the bottom of the
sheet.

My thought about how to approach this is to fill the gap with thinset
level with the face of the sheet, let that dry, and then apply the
mesh tape and another thin layer of thinset in the usual manner.

Is this the appropriate way to go about this? Or is there a better
way?

You're going to tape/thinset all of the joints ahead of time anyway, so just
do it with that variable joint as well. No need to do an extra step, and
you probably don't want to, either.

Assuming you're going to redguard afterwards, anyway. If you aren't going
to redguard it, then just tape/thinset when you set the tile.

Jon