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Unread 06-15-2014, 07:18 AM   #1
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Is this Kerdi drain flange going to bond correctly?

[[ Last edit: added more pics ]]

Noob here, looking to install a Schluter shower in a highrise ( conrete slab ). I did lots of research, but in the end, I'm not a licensed plumber, and can't afford any mistakes ( regarding code ), so I hired a contractor who claimed specialization in Kerdi.

I can't take much time off work, so I worked from home when he came for round one ( replace original off-center drain, feeding into copper, and install custom dry pack pan ). I figured I'm paying big money so I don't have to babysit the progress -- after all, that's the whole idea of a professional, no?

Anyway, a little while after he had finished and left, I wandered over to inspect things more closely, and noticed something I considered odd: a lot of the integrated fleece of the Kerdi drain flange, particularly the highest / outermost area, is covered in mud, which is conspicuously different from the official instruction manual photos and Schluter videos.

I thought the fleece is supposed to be left unmolested so that it can be properly bonded ( via thinset, with a 2" lap, like all other Kerdi lap, as specified by manuf ) to the Kerdi membrane that will be added next... but won't the drypack interfere with this? Is my concern unfounded? Why would a "pro" deviate from manuf's very clear instructions?

While I'm on the question-train to knowledge-town, what guarantees waterproofness when one Kerdi membrane is bonded to another? Is the thinset mortar ( between the overlap ) waterproof?

Also, the surface of the mortar bed looks pretty ugly ( small divots, little bumps, lateral "dents" from pressing a float too hard along its edge, etc )... are these all going to be sorted by the thinset between the bed, and the Kerdi membrane?

TIA for feedback.

( If it matters, the drain kit is ABS + SS. I didn't get a good look at the dry pack, but he mentioned Mapei, and it looked like packaging for Mapecem Premix or Topcem Premix that was used. It gave off tons of heat as it dried ).

I have included a pic of the flange, and another from a low angle so you can see the build-up on the wider outer rim ( completely covered ), as well as an example of what I consider a poor screed finish against the back wall, and an overview with the curb.

Outside, the curb rises 4" from slab base, and inside, the pan rises to 2.5", leaving a 1.5" "flood allowance" from screed to curb top. Most people say code specifies 2" min, and I mentioned this to the guy, but he shrugged it off; then again, I'm in Canada, so maybe our code is less strict for that?

The last pic is what I expected to see, having watched the official Schluter videos. The obvious difference is that the screed is level with the top / higher / outer part of the flange, but doesn't cover any of the integrated fleece.
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Last edited by bernz; 06-15-2014 at 09:11 AM.
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Unread 06-15-2014, 08:11 AM   #2
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Before the pros get here, can you post another picture further out showing the full shower base?

This does not look right to me based on what I have seen here.

Pros will probably want more pictures.
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Unread 06-15-2014, 08:19 AM   #3
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Hi Bernz and welcome.

What Ed said about more pictures and include the curb inside and top.

The mud is supposed to be floated flush with the bonding flange and the fleece is to be kept clean and free from what is seen.
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Unread 06-15-2014, 08:55 AM   #4
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It's pretty obvious from your one picture the person didn't know how to install a Kerdi drain or even a shower mud bed.
your going to have problems attaching the Kerdi to the drop off the mud bed and onto the flange part of the drain.
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Unread 06-15-2014, 09:28 AM   #5
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Thanks for the welcome and responses.

Brian, that's what I was afraid of. I don't see how a good seal will be possible when trying to bond the Kerdi membrane ( normally the next step ).

Any advice on how to deal with this? Should I contact Schluter? I already phoned the contractor to register my concern, but he gave me the standard "it'll be fine" response, and I wasn't convinced, which is why I've posted here.

Is there a way to salvage what exists now? I can't help but think that chipping away the surplus concrete would irrepairably damage the flange ( particularly the integrated membrane ).

It's pretty frustrating to have gone to the trouble of finding a "Custom Kerdi shower specialist" ( literally what is printed on his biz card ), only to see a result like this. Then again, I guess it's good to notice a potential problem before the next stages. *sigh*
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Unread 06-15-2014, 11:03 AM   #6
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Hi Bernz, welcome! A properly installed Kerdi drain should look like this. You want the Kerdi membrane to bond to the drain flange. I would make him redo it.
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Unread 06-16-2014, 04:45 AM   #7
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Thanks for those pics, Mike, that's the kind of thing I was expecting to see.
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Unread 06-16-2014, 05:40 AM   #8
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Im in Canada also.

I wont say too much about using tge mapecem. Ive done it too in the past, its what was recommended to me.
Its a pain to work with for a pan (which is one reason it shouldnt be).

I bet you don't have much slope, or at least not even? Especially flat near the curb and walls? That product has an almost self leveling quality to it which makes it terrible for making slopes. Even if its mixed real dry.
It sticks to everything and is very messy. Explains why its all over the flange.

Your contractor looks like he needs to spend some time here on the forum. I used to do things like that at one time, just didnt know better.

Pan should be redone with 5-1 deckmud (check liberry link) in my opinion. Drain might be fine if most comes off. Even if the fleece is damaged I think some kerdi fix should still bond kerdi to it.
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Unread 06-19-2014, 05:43 PM   #9
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So, I got in touch with Schluter, and they said, yup, based on photos, it's not done right, and wouldn't be Schluter-warrantied.

I talked with the contractor, and insisted it be fixed. We agreed on a fix that will involve him cutting out a square of mortar around the flange, removing the flange, and replacing with a new flange ( with new mortar to reach level with the flange, meaning the flange will be 1/4" - 1/2" higher than it is now ).

Ultimately, the shower floor will end up about an inch higher than it needs to be, IMO... ...but I can live with that. My main concern is having a proper bond between the main Kerdi membrane and the integrated membrane in the flange, and having the drain grate level with the rest of the "floor" ( Schluter rep confirmed that grate height is mildly adjustable ).

I don't understand why people can't just follow instructions... ...but life isn't perfect, so I'm dealing with it.

Thanks to all who replied, and hopefully anyone else with a similar concern will find this thread and glean some knowledge from it.

I'll try to post some updated pics after the fix.

PS. John, the contractor had an apprentice ( ? ) doing some ( maybe most ) of the work, and when I talked with him ( the contractor ), he admitted they had "spilled some on the lip" and then just "kept going" with it, so I agree that it seems despite his claims of having attended workshops and being a "specialist", he could benefit from more training. There is an okay slope on it, based on feel, but the work *is* pretty sloppy. Of course, if everyone had as much self-doubt and attention to detail as me, we'd still be using steam power, and the Internet would be hundreds of years away.

Last edited by bernz; 06-19-2014 at 05:52 PM.
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Unread 06-19-2014, 06:04 PM   #10
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Originally Posted by bernz
We agreed on a fix that will involve him cutting out a square of mortar around the flange, removing the flange, and replacing with a new flange ( with new mortar to reach level with the flange, meaning the flange will be 1/4" - 1/2" higher than it is now ).
The "Flange" he refers to is the drain. It is on the left.

Name:  Kerdi drain.jpg
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It can be cut out and replaced and maintain the original bed height.

Hope this helps

No curb, walk-in shower.
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Unread 07-11-2014, 07:15 PM   #11
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Hi again,

Yes, what I was calling the "flange" is indeed the large plastic ( in my case ABS ) piece into which the drain grate eventually nestles.

Anyway, to summarize, the guy came back, ground it down, the damage to the integrated membrane was minimal, so I agreed to let him finish the job without having to recast the pan.

TBH, I'm not happy with his work, but I'm out of gumption for dealing with this nonsense, and IME, when someone demonstrates incompetence, I don't expect them to suddenly change, and I just wanted the work done so he could GTFO instead of making it even worse. I obviously won't be getting him to do any further work, nor will I recommend him to others.

Thanks to everyone for your input. I *am* looking forward to the tiling bit, and will be back to ask some questions when I have time to continue this project.
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Unread 08-11-2014, 06:22 PM   #12
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Style and technical feedback requested on this design

Hi all,

First, thanks to those who responded regarding my Schluter installation fiasco ( lesson learned: "specialist" == "guy who thinks he knows what he's doing, but very possibly is clueless" ).

Now, I'm looking at the tiling.

I went to some tile stores to see what's available, and here's a mock-up of a ( not color-correct ) design I came up with... Please let me know what you think; this is only the walls, with primary tile size 12x12"; the floor will be 2x2 "grippy" stuff, slightly darker mono-color ( beige ) but with faint flecks matching the walls.

I plan to add two "bone" / "ivory" colored porcelain corner "shelves" as pictured ( they actually match the main tile IRL, but SketchUp absolutely sucks at color ), and the faucet / valve and shower head "runner" pipe holes are pictured in a plain color clearly visible in the first pic.

I'm primarily interested in technical advice ( eg. "hey, large thick tiles may cause load-bearing problems for Kerdi membrane" or something like that ), but style recommendations are also welcome.

I'm trying to keep the faucet "centered" ( it's actually exactly centered on the wall in which it resides, because the plumber who roughed it in actually knew what he was doing ), and I rather like symmetry, even to the point that I'm willing to do extra tile-cutting to make it happen -- for instance, the wall with the faucet / head is 35", so I intend to cut both the left and right columns in order to keep the faucet horizontally centered in its dark tile ( if you think it's a dumb idea for any reason other than that my time is potentially worthless, please explain, thanks! ).

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Last edited by bernz; 08-11-2014 at 06:28 PM.
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Unread 08-11-2014, 07:04 PM   #13
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i like that

chance you can put a nook in the dark squares on the back wall? foot, mid, high one, and ditch the shelfs then.
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Unread 08-11-2014, 07:35 PM   #14
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Welcome back, Bernz. It'll help if you'll keep all your project questions on one thread so folks can see what you're working on and what's been previously asked and answered. We can give it a more generic title any time you'd like to suggest one.

Would likely help, too, if we knew at what stage you are now with your actual shower construction.

Originally Posted by Bernz
I'm primarily interested in technical advice ( eg. "hey, large thick tiles may cause load-bearing problems for Kerdi membrane" or something like that )
If your Kerdi has been properly installed, you cannot reasonably overload it by installing ceramic tile that is too heavy. The minimum bonding strength of thinset mortar to Kerdi is 50 pounds per square inch. To exceed even that minimum bond, your 4"x4" tile would need to weigh in excess of 800 pounds. I doubt you run into any of those.

My opinion; worth price charged.

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Unread 08-13-2014, 06:07 AM   #15
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studderin, thanks, I really didn't have any cavities in any easy to reach areas, so I had to go with an "external" solution.

CX, thanks for gluing the threads together; I agree. As for the weight, that's good to hear... the installation did a pretty poor job ( IMO, but people are always telling me I'm a perfectionist )... there are some slight air gaps in small patches ( after the fact, I'm now certain the installer didn't actually understand the process, or got lazy, and didn't smooth out the Kerdi after the "paste-up" part ), but they are small in area ( 2 or 3 sq-inch ), so I think it'll be "okay"... 50 lbs / sq-inch is quite great. I totally believe in the product, I just wish I'd found an honest / skilled installer ( he even came recommended from someone I already trusted *sigh* ).
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