I'm renovating my shower and have decided to use Durock cement board to install tile on later. One of the walls is concrete block with a window. Is anything needed on the wall before installing the cement board or can I just screw it to the wall and go? Or would it be easier to skim set it then water proof it instead? I plan to use Maipei aqua defense as a waterproof membrane over the board, but I'm seeing conflicting information on how to prep the block wall.

  • If I didn't go with the cement board would I need to just skim coat the wall then use the aqua defense and then tile? I know I'm seriously over thinking this whole thing.
    – Payne
    Commented Nov 26, 2023 at 15:48
  • You only need to skim coat the block if the surface is very irregular. If you are using larger tile (12 x12 or larger), the irregularities can most likely be neutralized by a larger grooved trowel. ( 3/8 x 1/4 )
    – RMDman
    Commented Nov 26, 2023 at 16:45
  • OK got it! Thanks so much!
    – Payne
    Commented Nov 26, 2023 at 17:19

1 Answer 1


Tile sets well on block walls. There is not a requirement to cover with cement board, but if you feel you must, add firring strips and then the cement board.

I have used the Aquadefense on many shower projects. Always got good results.

Install the cement board. Use cement rated mesh tape on the corner of the block and cement board walls. Mud the corner. If the block is relatively flat, just coat with Aquadefense, (2 coats) and use a modified thin set for the tiles.

  • Sweet. Thank you!!
    – Payne
    Commented Nov 26, 2023 at 15:37

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