My installation: Cement-board = over the bathtup lip.

There's one-two spots where the cement-board is not not flush with the bathtub lip creating gaps behind few tiles are supposed to be. Can i just apply more Thinset mortar at those spots to compensate ? It's not huge, but just enough to bother me because it ain't flat. Thank you


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  • 1
    I would add some thinset and get it flat first let it dry then tile less chance of having a problem with the tile this way.
    – Ed Beal
    Mar 15, 2016 at 19:26
  • The backerboard was installed incorrectly, but we're past that now. Let the fudging begin.
    – Mazura
    Mar 16, 2016 at 1:49

1 Answer 1


Either your way or Ed Beal's are fine & do work. You just don't want any voids or unsupported portions of tile to avoid impact cracking or breaking. Back-buttering & going to a wider trowel notch should do it. But otherwise, mark your layout if you fill-in, to make sure you're actually filling to the row's edge.

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