This is the sink/dishwasher bay for my basement apartment. There will be a bottom and a top cabinet, corresponding approximately to below and above the green line. I want to put tile on the wall around, approximately where you can see the cement/backer board between the two green lines.

enter image description here

I understand that, in situations where drywall meets cement board, you typically want to overflow drywall onto where the tiles will be as the tiles can go on drywall but it's hard to emulate a smooth surface of a drywall wall on cement board.

However, this is a little different because there will be no visible delineation, i.e. everywhere where there are no cabinets, there will be tile. So my reasoning was that by reversing the rule from the previous paragraph, I can avoid having to tape join the two substrates. However that introduces the problem of uneven transition between the two (I think the backer board is 3/8" and drywall is 1/2").

In this particular case, is it okay if the cement board overflows the drywall (green line) or should the drywall overflow on the tile substrate (as though the cabinets went below and above the red line), as is normally done?

  • The cement board should also be 1/2". I've seen 1/4" also, but never 3/8. Are you sure? – isherwood Dec 5 '18 at 17:19
  • I think it says 1/2 but it's really 3/8 – amphibient Dec 5 '18 at 18:04
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    This is why i use Denshield for tile on walls and not cement board. It is the same thickness as the dry wall and you score and cut it the same way. – Alaska Man Dec 5 '18 at 19:46

I see no problem at all with your plan, even if there's a 1/8" thickness variation. That's not enough to tilt your cabinets substantially out of plumb. If it's a concern you can always shim behind the cabinets, since any resulting gap will be covered by the tile.

  • So you're saying it's okay the way it is? – amphibient Dec 5 '18 at 18:04
  • Also, do you think it will be okay to not tape the joint between the drywall and cementboard ? – amphibient Dec 5 '18 at 19:25
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    The only reason I can think of to tape it would be to add stiffness. If it feels plenty stiff as it is, don't bother. – isherwood Dec 5 '18 at 19:33
  • so just to confirm, you're saying it's okay if I leave it the way it is under the green scenario above, cementboard tucking under the cabinets and then no tape between it and the drywall? correct ? – amphibient Dec 5 '18 at 19:36
  • You may want to tape it if you think insects can get through which depends on what's on the other side of the drywall. Make sure the tile is caulked where it meets the counter top. – Platinum Goose Dec 7 '18 at 17:29

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