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Unread 06-29-2022, 06:45 PM   #1
Krisola
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Plan for new curbless shower, concrete slab on grade

Hello! I've been lurking for a while, learning a lot and now I have some questions regarding the bathroom we are installing from scratch. Basic details:
  • Room dimensions: 107” x 74”
  • Will have a curbless shower at one end of room, 36” x 74”
  • Subfloor: slab on grade concrete with recess/drain cast-in, as well as a basic ‘pre slope’
  • Walls: new construction, standard framing (bare studs)
  • Drain: Sioux Chief

The floor in the bathroom area is recessed, so I’ll need to bring the floor tile up to match the height of the polished concrete floor in the main room. I only have about 2” to work with in the recess, from the current concrete subfloor to the top of the existing polished concrete floor in the hall. Based on this, I dont think I have the room to do deck mud below (preslope) and above the water-proof liner (I have a reference link but cant post the url yet).

I realize that there is no One Recipe to Install Tile (to rule them all) that applies in all scenarios, and that different tile experts develop their own recipes (with preferred materials, etc) that work for them. With that in mind, do you see anything in my plan that is likely to lead to failure?

My plan:

Plan version 1 - Membrane direct on concrete slab (slab acts as pre slope)
  1. Drain flange (already installed with concrete slab which also has minimal pre slope)
  2. Install waterproof membrane on concrete slab (latricrete hydroban, using the recommended adhesive)
    • Membrane up side of walls approx 18”, over entire floor
    • Silicon to seal membrane against the lower drain flange
  3. Install clamping ring on drain system (over membrane)
  4. Install adjustable drain ring - set final height
  5. Install deck mud for final slope
    • Bonding layer (adhere deck mud to membrane) - thin set
    • Slope to low point at drain
  6. Tile on deck mud


Plan version 2 -Membrane on deck mud (deck mud acts as pre/final slope in one)
  1. Drain flange (already installed with concrete slab which also has minimal pre slope)
  2. Install deck mud for final slope
    • Bonding layer (adhere deck mud to membrane) - thin set
    • Slope to low point at drain (will need to leave room around drain to install clamping ring, etc)
  3. Install waterproof membrane on deck mud (latricrete hydroban, using the recommended adhesive)
    • Membrane up side of walls approx 18”, over entire floor
    • Silicon to seal membrane against the lower drain flange
  4. Install clamping ring on drain system (over membrane)
  5. Install adjustable drain ring - set final height
  6. Fill in gap around drain with deck mud or thin set (I have a reference link but cant post the url yet)
  7. Tile on membrane (per laticrete spec for membrane, I have a reference link but cant post the url yet)

Questions:
  1. Is there a structural or adhesion advantage to installing the tile directly on deck mud (plan 1) vs membrane (plan 2)?
  2. Is having the membrane fully sloped a strict requirement? Keeping in mind this is a slab-on-grade construction where the bath area is already recessed relative to the main floor (which is also concrete) - literally a concrete tub. The only issue here is that the existing concrete ‘tub’ floor is not fully sloped.
  3. For plan version 2, is there a disadvantage to having to do the last bit of fill around the drain (step 6)?

Input greatly appreciated!
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Unread 06-29-2022, 07:00 PM   #2
jadnashua
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The national plumbing code calls for a minimum of 1/4" per foot for a shower. FLorida tends to ignore that on a recessed slab. You should modify your profile to put your general location in as that can help.

If you can't or don't want to change the shower drain to one designed for a sheet membrane, then you can use the divot method. Http://noblecompany.com/products/nob...drain-flashing Or, Schluter makes a clamping drain coversion https://www.schluter.com/schluter-us...KERDI_DRAIN-AR

A bonded mud bed over concrete is the best way to make your shower have the proper slope at the desired height.
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Unread 06-30-2022, 11:10 AM   #3
Krisola
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Profile modified as suggested - I'm in Oregon.

I do plan to follow the 1/4" per foot slope (cross-checked against local building code, but I believe this complies with local code) and the selected drain (a Sioux Chief) is designed for a sheet membrane.

My main question is:

In my application (slab on grade, recessed area for bathroom floor, floor surrounding bathroom is polished concrete slab on grade) - can the membrane be installed directly on the recess area, with deck mud on top (setting slope), then tile on mud OR should the deck mud set slope first, then membrane on sloped deck mud, then tile on membrane?

I've attached a drawing to hopefully clarify what I am referring to.

Thanks!
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Unread 06-30-2022, 01:48 PM   #4
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Hi Kris,

Do you want the shower floor even with the bath floor at the shower entrance?
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Unread 06-30-2022, 02:26 PM   #5
Krisola
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Yes! The plan is to have the same tile across the entire bathroom floor and the transition across the 'threshold' into the shower area should be seamless... (one post away from being able to post links to example images...)
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Unread 06-30-2022, 02:28 PM   #6
Krisola
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Here are some example images that show the type of level transition from main bathroom area into the shower area that I plan on:
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Unread 06-30-2022, 03:03 PM   #7
Tiger Mountain Tile Inc
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Sioux Chief is a brand but that doesn't tell us which drain that you are planning on installing. Can you post a link to a particular model of drain?

For a curbless shower, there are only a couple of ways of doing them that are approved industry methods. A liner with a preslope isn't one of the methods.

So you're going to have to go with a topical, bonded waterproof membrane and tie it into the drain.

Can you post a couple of photos of what your space looks like?
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Unread 06-30-2022, 03:39 PM   #8
Davy
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Your plan #2 looks like a divot drain.
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Unread 06-30-2022, 04:09 PM   #9
Krisola
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I will take pictures of the space after work and track down the specific model of drain.
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Unread 06-30-2022, 04:14 PM   #10
jadnashua
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Remember, the tile is not the waterproofing layer, so the liner or tileable membrane must have the required slope. A conventional liner is not an industry approved method to make a walk-in shower with no curb. Unless you use a surface membrane, with the conventional liner, there's nothing to prevent moisture from getting beneath it from the edges.

As I said, it seems like you have two choices if you don't want to take the existing drain out. Use the divot method, or use the Kerdi conversion drain. My preference would be to use the Kerdi conversion drain.
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Last edited by jadnashua; 06-30-2022 at 04:37 PM.
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Unread 06-30-2022, 09:50 PM   #11
Krisola
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Alrighty - update:

The drain that I am using is a Sioux Chief Finish Line Adjustable Floor Drain Sch. 40 Hub Connection (5 1/2"): https://www.siouxchief.com/products/...hub-connection

The install instructions (as I read them) has the water proof sheet membrane running over the lip of the bottom drain piece and secured with a clamping ring.

I've attached some pictures of the the concrete recess area for the bathroom.

A question re terminology:

jadnashua used the terms "conventional liner" and "surface membrane". I plan on using the Laticrete Hydrogen sheet membrane, which I understand to be a waterproof surface membrane. Is this correct? And I would run the sheet up the side of the walls as recommended (I've seen a recommended 6-18" up the walls - I'd err on the side of cautious )

And jadnashua - I'm curious to hear why you would recommend the Kerdi conversion drain over the divot method!
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Unread 06-30-2022, 10:46 PM   #12
jadnashua
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Technically, both Kerdi and the Hybroban sheet membranes are only certified as a SYSTEM. Meaning that if you use it, you should do the walls at least up to the height of the shower head. If your inspector was being picky, if you didn't use the membrane the way it was designed and certified, it shouldn't pass an inspection. CBU isn't waterproof, either, but is not damaged by being wetted. With the lower part with surface waterproofing, if any got behind it, it could only escape out the back of the shower, and that often doesn't end well.

With the Kerdi conversion drain, you won't end up with a chunk of mortar the depth of the divot at the wettest location of the shower as all water ends up being directed right over it.

Both systems will work, but I prefer the whole enclosure to be waterproof right beneath the tile.

With either system, you need to be very careful about waterproofing that membrane to the drain. I think it's more reliable with the Kerdi drain, but do not have any imperial experience to back that up.
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Unread 07-01-2022, 05:37 PM   #13
Krisola
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Great info - yes I plan to fully waterproof the walls to the ceiling using the laticrete hydrogen board (sticking with one system, waterproofing all the surfaces).

"... I prefer the whole enclosure to be waterproof right beneath the tile." <-- 100% this!
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Unread 07-08-2022, 10:50 AM   #14
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Thanks for the link. Unfortunately, that drain isn't compatible with what you are building. You need a bonding flange drain or to make a standard clamping ring drain with a divot like Davy posted above.

The Kerdi drain that Jim mentioned is a good choice. So is the FloFx drain. So is the Noble drain. The Laticrete drain didn't get great reviews. Not sure if they've fixed it, or not.

FYI, what you're building isn't really the conventional way of building a curbless shower. Typically, the slab will be cut out and recessed.

I'm guessing you feel the concrete is already adequately sloped in the shower area? Are you planning on waterproofing the entire floor?

edit: I just noticed the whole slab is recessed in the bath area. So, you're planning on drypacking the whole floor to be even with the slab in the adjoining room?
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