We installed cement board on a wall to prep it for tiling.

window with gap

The gap between the window and the outline of the rough opening is anywhere between 3" to 3.5" (it's inconsistent).

I want to install narrower casing than what was there before and also to eliminate the apron entirely.

Is there a way to patch or bridge the gap with cement board while not setting up a situation that will lead to grout cracking?

  • You should have thought about this before installing the cement board. Your best bet at this point is to remove the adjacent pieces of the cement board and install new ones that are fitted closer to the window opening. Note that if you mean to replace or re-do the apron under the window to get that done before re-fitting the cement board. – Michael Karas Apr 29 '17 at 19:48
  • I agree that I should've thought about this before. Could you clarify what you mean about redoing the apron before refitting the cement board? What part of the apron needs to be handled before the cement board is installed? – S.S. Apr 29 '17 at 20:11
  • The ears of the apron that stick out to the left and right sides of the window. They currently extend over the area where the cement board should be. – Michael Karas Apr 29 '17 at 20:41
  • Isn't it the stool that has ears, not the apron? And I thought that the stool ears are supposed to extend out over the wallboard, and that they should abut the wall board directly. – S.S. Apr 29 '17 at 21:05
  • OK. I guess I referred to the part with the ears. Yeah that is the part you would typically deal with after the cement board is in place. – Michael Karas Apr 29 '17 at 23:00

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