I have poured the preslope on the cement floor, and installed the Oatey PVC membrane and 3 piece drain.

I would like to use Kerdi board on the walls, but not the floor. Can I install Kerdi board next on the walls bring it down to the membrane?

After the Kerdi goes in, I would pour the final slope for the shower floor and tile overtop.

I like the Kerdi product for my walls because of the pre-fab niche, and lightweight materials and smaller board sizes that are available. I really don't see any videos of people installing Kerdi board with an Oatey membrane. Are the two incompatible for some reason?

  • i would just redgard anything that left me in doubt; money well spent.
    – dandavis
    Aug 8, 2019 at 16:45

1 Answer 1


That makes sense the installation video from Oatey says "wateproof drywall or cement board" but your kerdi board is waterproof too, so it's equivalent.

Be sure not to screw through the shower liner--if you need to screw low on the Kerdi board put a dwang (cross-block) in above the liner and screw to that.

  • Thank you for the prompt response and dwang recommendation. I was worried about perforation of the membrane so inwill keep the kerdi fasteners above the 6 inches of membrane. Assumption is that the mprtar bed for final slope will also apply pressure to the lower inch or so of kerdi?
    – JoeDubya23
    Aug 8, 2019 at 19:45
  • Follow up question. Thanks CX. Follow up. In this hybrid configuration what ddo I install in lieue of corner dams on my curb? I see Kerdi makes a product, but so does Oatey. Given that the dam curb is where my kerdi walls meet my membrane curb, what product should i use for a dam? And what adhesive as well....
    – JoeDubya23
    Aug 9, 2019 at 20:33
  • there's a dwang, then then the membrane then the kerdi so putting mortar against the Kerdi just pushes it against the structure behind it, so no problem, for the corners use the Oatey corners because they need to seal to the Oatey membrane
    – Jasen
    Aug 9, 2019 at 20:59
  • Oatey recommends an x-15 bonding adhesive for their pvc layer...this is fine for the dam corner on the curb, but what will stick the dam corner to the kerdi? Will the same adhesive work or should i use thinset and kerdi tape for that seam?
    – JoeDubya23
    Aug 9, 2019 at 22:41
  • keep the membrane adhesive away from the kerdi, finish the membrane first according to the Oatey instructions, use the kerdi tape to install the kerdi board,
    – Jasen
    Aug 10, 2019 at 2:57

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