I originally planned to finish my shower floor with deck mud, shower pan liner, concrete mix, RedGard, mortar, and tile in this order:

  1. Pre-slope with deck mud
  2. Shower pan liner
  3. Post-slope with concrete mix
  4. RedGard
  5. Thinset Mortar
  6. Tile

However, I now don't think I can do a pre-slope because my shower drain is flush to the subfloor level. The examples I found with a pre-slope all had 1 to 2 inches to work with for the pre-slope. However, now I don't have room for it.

Given that I'm know thinking about using the Schluter-Kerdi floor system which I believe is already sloped.

My question is, can I still use the shower liner with the Schluter-Kerdi system? So, something like this

  1. Shower pan liner
  2. Schluter-Kerdi Shower Trays (already sloped)
  3. Thinset mortar
  4. Tile

With this there would no be RedGard (I've read that it's not a good idea to use it with Schluter-Kerdi).

enter image description here

  • You're much better off asking that at the John Bridge tiling forums (although it's not as active as it once was). I'm not 100% picturing what all you want to do but I will say Schluter is a very complete system and generally if you mix other systems into it, it makes things more difficult and typically worse. So just make your life easier and use all Schluter stuff. Commented Oct 5, 2023 at 12:09
  • Also you don't want to have a layer between the shower liner and redgard. One waterproof layer and everything above it is routed into the drain. Commented Oct 5, 2023 at 12:21
  • Pics of your situation would be helpful. Not all showers are the same. Post some pics and a list of materials you plan to use for the walls to get useful info that is pertinent to you.
    – RMDman
    Commented Oct 5, 2023 at 12:32
  • Your first 6 steps are exactly what I did. However, as you note, it requires your drain to be standing proud of the floor by a fair amount. My recommendation: lift the drain up to the proper height. It would be less pain to do that, versus getting weird with everything else. Also, Schluter is an expensive way to go.
    – Smith
    Commented Oct 5, 2023 at 13:46
  • Thanks everyone. I added a picture of my situation.
    – ptownbro
    Commented Oct 5, 2023 at 21:55

2 Answers 2


To use a shower pan liner you must have what is called a 3 piece drain. This will allow you to put your shower pan liner to the drain. A 3 piece drain also has threads where it can be raised or lowered for the final install so it comes out flush with the tile.

  • Hello, welcome. You could improve your answer by posting a picture of one. Then everyone will know what you mean, right away. Commented Nov 15, 2023 at 4:21

Oatey makes a product called "Perfect Slope" that will bail you out. Here's a picture from their product page demonstrating its use with a flange mounted flat on top of the subfloor:

perfect slope product

  • Great. Thank you
    – ptownbro
    Commented Nov 22, 2023 at 1:38

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