[limiteddi]

Plumbers made a mistake by placing a mixer vertically when it was supposed to be horizontal. I had to remove 3 tiles and some cement board in order to the mixer. Now what everything has been positioned properly, there is no base to install the tile onto. To reinstall the cement board I would need to remove more tiles that I am trying to avoid.

What can I use to create a base for tile installation?

 

[udraft]

Well cement board is pretty rigid, I would expose a bit more stud, straighten up those raggedy edges and cut a new board to the odd shape. Silicon between the board and the fixture.