Filing in gap in cement backer board for tub surround

[TomYoung]

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?

TIA.

Tom Young

[Steve Barker]

Just fill it with the thinset you set the tile with.

[Jon Danniken]

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

[keith]

All joints should be taped, not just filled in with mud. The tape is a heavy-duty version of the nylon mesh that's used for sheetrocking.