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Schluter Kerdi on regular drywall

this_page_left_blank | Posted in Mechanicals on

I’m going to use the Schluter Kerdi system for my shower, mainly because it’s less work and seems more fool proof than the traditional mortar bed. Prior to this, I always considered waterproof drywall a must in the bathroom. The manufacturer says regular drywall is fine because the Kerdi membrane is waterproof. Looking for opinions, would waterproof drywall behind Kerdi membrane be insurance or overkill?
If Kerdi over regular drywall is acceptable, is it preferable to waterproof drywall alone for the rest of the bathroom? The advantage I see is that the membrane is continuous around corners, unlike Hardie Backer or DensShield.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Trevor,
    I think you know the answer to your question about Schluter Kerdi over drywall. The manufacturer of the waterproof membrane permits this approach, and it works. There is no reason to use another type of drywall.

    Q. "Is it preferable to waterproof drywall alone for the rest of the bathroom?"

    A. If you are talking about walls that aren't covered by tile or Schluter Kerdi membrane, many builders like to specify moisture-resistant drywall for these walls. It's not required, however -- especially if homeowners are conscientious about housekeeping and use of the bathroom exhaust fan.

    If the homeowners have a family with lots of kids, some of whom engage in play that involves splashing, moisture-resistant drywall makes sense.

    1. Bosman111 | | #4

      Hi Martin,
      I too had a question about this. I know Schluter allows kerdi over drywall but does R702.4.2 preclude this install?

      Thank you,

      Kevin

      1. Expert Member
        MALCOLM TAYLOR | | #5

        Kevin,

        R702.4.2 lists materials allowed to be used as tile backers. But the gypsum isn't the tile backer, it is the substrate behind a proprietary tile backer (Schluter's membrane). You could use anything Schluter allows in their installation manual.

        1. Bosman111 | | #7

          Thank you Malcom!

          1. Expert Member
            MALCOLM TAYLOR | | #8

            Where would the fun be if codes were straightforward?

  2. user-6623302 | | #2

    Keep looking for wall system products. I was at a builder show last spring and saw several products which looked easier/better than the Kerdi. They were complete systems of wall panels and pans which were ready for tile. I did my shower with Kerdia about 15 years but used cement board. Why fool around with guessing if drywall will work. Remember you need good ventilation.

  3. this_page_left_blank | | #3

    Martin, I was only planning on moisture resistance around the shower and the tub, behind tiles. I don't know why I said the rest of the bathroom. I was just wondering about KERDI vs waterproof drywall in the non-shower area, i.e.. the tub surround and backing walls. I've decided to just have the drywaller install standard stuff, I'll go in with the KERDI afterwards.

    Jonathan,

    I appreciate the suggestions, but I'm not in a position right now to spend a long time looking around for things. Schluter is ubiquitous, customizable and seems decent. Pre-made systems aren't going to be the exact size I need. Maybe you can special order them to size, but I'm sure you pay for that in both lead time and dollars.

  4. natesc | | #6

    Definitely use regular drywall. The big issue with cement board is that the thinset will skin over really quickly. Moisture resistant can cause similar problems, and there is absolutely no advantage to it.

    I have used kerdi, and I have applied it over cement board. Kerdi is not a user friendly product, and when you shrink your working time down it is downright stressful.

    I believe it is Laticrete that has a liquid applied system with an integrated drain flange. You just paint that stuff on, and use fiber tape to reinforce all the corners. Way less of a headache in my opinion.

    The real genius in all these systems is the integrated drain flange that face seals the mortar bed. The old system of draining under the mortar bed was prone to issues.

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