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Unread 03-24-2020, 09:49 PM   #16
smifwal
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Brick is done on concrete, you adhere the bricks to the concert with thinset mortar. I guess you could use them on wood if you screwed down the first course. But 2x4 work just fine
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Unread 03-25-2020, 08:15 AM   #17
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Concrete structures want to be monolithic for greatest strength and crack resistance. There's actually a lot of science associated and cement itself is a unique animal because of its curing properties. By intersecting the monolith with big chunks of steel, you've provided specific weak areas for the concrete to crack along. Very similar to control joints cut in slabs.

If I were doing a mortar curb, I'd use lath. If I was needing to do a concrete curb like you're doing, I'd use fiber reinforced concrete, typically marketed as "crack resistant".

The "more is better" approach is sometimes not. In this case, the wheel has already be invented and perfected through proven methods. If it needed improvement, it would have been done by now.

To your question about cracking in two weeks. I'd be surprised if it didn't, but stranger things have happened. It's a bit of a crapshoot so we really can't advise well. Will if fail? Dunno. When one invents their own methods, I suppose they implicitly agree to be the tester as well.
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Unread 04-01-2020, 08:57 PM   #18
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new question. i got the shower pan built but i had a little issue with the kerdi drain. I wanted to lower one edge of the flange by about 1/8" to get it to sit level. I'd read somewhere that you can use some long screws through the holes in the flange to pull down an edge and then the day after building your shower pan, you take the screw out.
well i tried that and as you will probably guessed, the edge of the flange popped back up. so i went ahead and lifted the flange the rest of the way out.

now my plan is to go into the crawl space, cut the vertical pipe that goes to the drain so that i can completely remove the kerdi drain. then i'll clean up the shower pan and rebond the flange down flat. once it sets up, i'll reconnect the pipe with a flex coupler in teh crawlspace.

my question is, should i stick with thinset or is there actually something better to use now that i have the chance. i know thinset is usually the most convenient thing to use because its is what you use to put the kerdi down anyways. but in my case, it would actually be more convenient to use something like a construction adhesive or kerdifix and i would think that would bond to the plastic and shower pan better.
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Unread 04-02-2020, 06:25 AM   #19
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Definitely not construction adhesive, Jason.

I think you're going to need to base your next steps on what the section of Kerdi under the drain flange, and on the underside of the flange, looks like once you remove the drain. If the fleece face on the floor membrane and on the bottom of the drain flange is torn/shredded you won't be able to get a good bond/seal.

I'm pretty sure Kerdi Fix isn't intended for the use you're considering.

Worse case: you may need to remove a section, say, 2X2 of the floor Kerdi from around the drain, install a patch which overlaps the removed section by at least 2", and install a new drain.
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Unread 04-02-2020, 07:54 AM   #20
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sorry i may have not been clear. I didn't build the shower pan from kerdi. this is a mud-bed pan i built, so there is no kerdi under the drain.

the bottom of the drain flange is smooth pvc (i think?) so it shouldn't be damaged at all from removing it.

i was not at the stage to install the kerdi membrane on the shower pan yet so i don't anticipate anything being damaged by removing the drain now.

during install, i already had the flanged glued in place so i couldn't squish it down into the mortar. instead, I used a small putty knife to coat the bottom of the flange with unmodified thinset before i packed in the sandmix.

Also, i was thinking more about my original question where i suggested using some type of construction adhesive. I know I don't want something flexible for this application, I am thinking of some type of rigid setting epoxy that is meant for bonding to concrete and plastic. If thinset is really the best option, I'm fine going that route still...
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Unread 04-02-2020, 09:17 AM   #21
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Jason, I must be confused about what you've got, too, because I can't figure out why you didn't just leave the screws you put through the Kerdi drain flange to hold it level. Not the cleanest approach, but shouldn't be a problem if it works. And I'm not seeing what you plan to "bond" the flange to that will hold it in place if the drain riser is not plumb. You want to bond it to the mud bed?

Nothing at all wrong with the method you used when building your shower floor. I am almost always over a concrete floor with no access from below and I, too, just glue my drain to the riser and then pack mud under the drain flange. Works fine.

My opinion; worth price charged.
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Unread 04-02-2020, 10:02 AM   #22
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the drain riser is not plumb, but i'll be fixing that by cutting it and then once it is bonded down and set, i was planning to reconnect the plumbing with corrections to get it lined up stress-free. i have a 4' crawl space to work in.

I took the screws out based on another post I read where that was the recommendation and also because the head of the screws would have been a high spot since i didn't countersink the holes first.

i know the right solution would have been to fix the plumbing first so that i didn't have any upward pressure on the flange. hindsight...

maybe I'm misunderstanding the term "bonding flange" that schluter uses. For this system to be reliable, it seems like the drain flange should be bonded to the shower pan and not just rely on gravity to hold it in place.
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Unread 04-02-2020, 10:39 AM   #23
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Bonding flange, to Herr Schluter, means a flange to which their Kerdi waterproofing membrane can be bonded.

There is no need to attempt to bond the bottom of the flange to your mud bed, although some of the newer systems make the bottom of the flange mortar-friendly as well. If you bed your drain firmly into the mud bed or pack your mud bed firmly under the flange, there is really no need for bonding. That's:

My opinion; worth price charged.
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Unread 04-02-2020, 12:25 PM   #24
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so just pull it out, clean up the mud-bed so that the flange will lay flat, and then reattach with thinset which is really just there to provide a uniform support to the flange...

just makes me nervous, especially with the crawlspace access, i would hate to bump into the p-trap years from now and have it pop tile loose in the shower.
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Unread 04-03-2020, 09:23 AM   #25
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Jason, I'm not sure this is helpful now, but if I'm working with accessible crawlspace, I always cut plumbing back a ways and plan on hooking back up after packing slope. Usually just before flood testing. That way anything that goes down drain ends up in crawlspace and not the trap.

Early on in my Kerdi career I had some concern about flange not actually bonding to slope, but honestly have never had one come loose when reattaching plumbing. For peace of mind I now scuff up backside of drain flange with coarse sandpaper. Does it do any good? Dunno, but I know it does no harm.

Part of what holds drain assembly in place is the mortar pushing up through perimeter windows, which should be flush with pan. The Kerdi applied on top kinda sandwiches flange with thinset bonding on top side of dry pack mortar in said windows.

If I were doing for client, I'd probably figure on taking whole pan out and starting over, but if you can make the flange flush with pan the resetting with mortar may work. I would certainly not try this with drain pipe attached.

Another possible problem is the stub of pipe that's now glued into the drain. Depending on how far it drops to trap, you may not have room for coupling.
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Unread 04-06-2020, 09:27 AM   #26
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removed the drain flange, chipped away at the mortar bed to make a little room for some thinset and to allow room for adjustment. reinstalled the drain with unmodified TEC full set plus. 2 days later, installed kerdi with the same unmodified.

i have a couple small "bubbles", ~3/4" diameter. Do i need to worry about these or is that ok to tile over since the rest looks to be bonded really well. when i checked coverage it looked good.

if i need to fix those, do i just slit the kerdi and squeeze some wet thinset in?
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Unread 04-06-2020, 10:01 AM   #27
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By "bubbles" I assume you mean unadhered membrane. A great big no on slitting membrane and forcing mortar into wound.

Excise unattached Kerdi and apply Kerdi patch that extends at least 2" from edge of cutout. Use thinset to bond patch.
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Unread 04-06-2020, 10:09 AM   #28
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there is so much misinformation on these products. the "slit membrane and pack thinset in" direction was directly from another post, i think from a different forum though.

Either way, i know the repair would require a patch of some sort over top to stop water ingress.

thanks to all for the helpful comments thus far. there is a big difference between watching videos of this process and actually doing it. I was originally considering the shower as just a minor part of a huge remodel i've been doing but it has turned into quite a rabbit hole of learning.
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Unread 04-06-2020, 10:30 AM   #29
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Yes, the web has lots of info, both good and bad. That's the nature of the beast, I suppose.

FWIW, it's one of the reasons I read and post here. Good info, from folks who've actually done the task at hand, and also understand conceptually how products are designed to be used. Not to mention reading and comprehending manufactures' installation instructions.

After using mortar, I think you'd agree that "packing into slit" would be a fool's errand and provide no benefit. Portland cement is not glue. The mechanical bond provided by the fleece on the membrane is what makes the whole process work.
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Unread 04-06-2020, 11:11 AM   #30
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maybe dumb question. What is kerdi patch? is that a specific product or is it just a small piece of the same kerdi membrane i already used? Also, is there a difference between kerdi membrane and kerdi-band other than the dimension of the sheet?

i have a bucket of TEC liquid membrane that i was going to use on the screws and joints on the densshield wall. i also have a roll of 6" fiberglass membrane fabric that i was going to embed in the liquid membrane.

What would you recommend I do to waterproof the joints between the kerdi on the pan and the densshield wall? i was going to use the fiberglass fabric in the TEC liquid membrane but would it be better to cut 6" strips of my left-over kerdi instead and thinset it in place?

thanks again!
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