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Unread 09-20-2017, 03:58 AM   #31
Atto
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Hmmm, based on the accolades, I returned the All-Set and got some 317 for my porcelain-over-ditra thinset.

Thanks,
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Unread 09-10-2020, 11:12 AM   #32
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Schluter’s MODIFIED all-set for Kerdi and ditra

I’ve been away from schluter for a while, been using other products. While the whole thing about using unmodified with Kerdi isn’t new, what is (to me) that they have a modified thinset you can use with ditra and Kerdi.

Excuse my snarkiness, but now that they sell a product it’s ok to go modified? I must be missing something.

Thanks...
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Unread 09-10-2020, 11:24 AM   #33
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When you read the instructions, they say latex-modified thinsets, which need to dry to attain their stability and full strength should not be used. There are at least 4 different classes of modifiers used in thinsets today, and some of them will work just fine between, or on top of a membrane like those from Schluter. It's just that the average person will not delve into the TDS or understand what it's saying, and the ANSI specs do not differentiate the types of modifiers, so there's no easy way to identify suitable mortars. Plus, since Schluter has no control over the formulations of mortars sold by others, if they published a list of compatible mortars one day, the manufacturer could change things up and never notify Schluter, and then things could go south.

So, if the modifier does not need to dry to become stable (the cement will cure, regardless), it will work reliably.

Their testing has also proven that a premium dryset mortar will work on top of their membranes, tends to be less expensive, and readily available. Particle sizes, and the amount of cement to aggregates ratio and other things make a difference. Portland cement is a rough recipe, it is not a specific one, so there can be differences in that as well. Sort of like how many different chocolate cake recipes there are...some are better than others for certain conditions.
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Unread 09-10-2020, 11:28 AM   #34
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Kevin, I've combined you with one of the threads on Schluter's mortars.

You still hafta read the Schluter instructions. You can use the Schluter modified thinset mortars with their membranes, but they still won't give you a warranty if you use anyone else's modified mortars.

Of course, many (or most?) other manufacturer's mortars will still work as well with the Schluter membranes.
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Unread 09-10-2020, 03:23 PM   #35
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Sounds good on rolling my thread into this one CX.

Appreciate the clarification Jim. Throughout the Schluter Installation Guide I just received with a Kerdi tray, the language says to use one of the Schluter thinsets or an unmodified thinset. In the Thin-Set Facts section they do say that if it’s between a latex modified thinset and unmodified thinset then use unmodified. But why is the comparison with LATEX modifieds? Strangely they really honed in on latex modifieds.

I happen to use mapei thinsets, so I reached out to them. Basically their LHT, LFT, and ultra flex thinsets are all fine as their not LATEX modified. Tech support guy pointed out that they’ve been recommending these for years with Kerdi. Scanning their site it seems you only get into latex modifieds if you add the “milk”, their liquid.

Looking at the specs for laticrete and mapei membranes they both say to use a polymer modified thinset. Nice and simple.

One more thing, this facts section in the guide incredibly says to only use unmodified with tile over their board and membranes. Who would do that? Especially larger tiles. But their modified thinsets are fine. (!)

I apologize if these points have been beaten to death before. But this is odd and confusing.
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Unread 09-10-2020, 07:24 PM   #36
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Kevin, if you'll read the installation instructions for all other waterproofing, crack isolation, or uncoupling membranes you'll find they require the use of a modified thinset mortar meeting ANSI A118.4. Well, except for the USG Durock Shower System membrane, which allows either. Or did.
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Unread 09-10-2020, 09:33 PM   #37
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Schluter's modified mortars are different than everyone else's because they're "specifically designed" for their products.

Kevin, perhaps you need a refill on your orange Koolaid?
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Unread 09-11-2020, 07:48 AM   #38
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What jadnashua says make sense and I have hear it before. I can buy it, but it does NOT make any sense when talking about adhering the tile to the TOP of the membrane. Can't the modified mortar dry out from the inside out, through the tile and grout joints or spaces if you wait to grout??

I think it is a combination of POSSIBLE fact along with keeping the installation proprietary.

With respect to keeping the warranty, I would like to hear JUST ONE case of where it was actually honored. If it was ever honored, I would imagine they just replaced the Schluter materials used, which is a very small percentage of overall installation cost (again, just my assumption). Someone can read the warranty and find out.
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Unread 09-11-2020, 01:59 PM   #39
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To make a point, Schluter took a clear glass plate and using a latex modified thinset, set the plate onto Ditra. It took nearly three months for the modifier to dry out all the way to the middle of the tile. Now, a good porcelain tile is nearly as impervious as glass, but would still allow a little moisture through it whereas glass would not. The plate was not grouted, so was open all around the edges.

The crystalline spikes that grow as the result of cement curing are fragile...they're coated with the modifier if you mix the thinset properly. They provide some stability to the crystals, and a little flexibility plus, can act like a glue to help enhance the bond. Until the modifier stabilizes, they cannot perform their job. So, while the thinset will dry (if required, not all do) from the edges in and are fairly rigid, on a microscopic level, the crystals are miniscule and can break, weakening the bond.

So, while to meet the demands of all of the Eurozone, Schluter could not get approval to use an unmodified, the specs on their mortars does allow a distinction on what type of modifiers are used, and they can say use X anywhere in the whole Eurozone. In the USA, they only had to run tests for one national agency to get the unmodified approved, without having to do that for numerous individual countries in the Eurozone. That's one reason why some people point to the differences, and wonder why...getting a consensus and the fact their thinset specs are able to differentiate suitable mortars. Schluter is really conservative. User's demanded modified mortars, and while it took a long time, Schluter relented, and provided something they know will work to fulfill that demand.

The way I look at it is this: the bond to the tile is FAR stronger than the bond to the fleece on say Kerdi, and there is NO bond to Ditra...so, which bond will break first? Not the one between the tile and the mortar except where possibly, the substrate is not strong enough and you get excessive flex. The crystalline structure of cement can flex a little, but should you exceed the limits, they fracture.

Whenever they start up their training classes, it's a good idea to at least make the effort to go to one, and then you can ask them your questions directly.

FWIW, there aren't very many latex modified mortars out there today anymore, but for the average guy, there's no easy way to tell what is used in them, and there's no way to just list an ANSI spec that says what is suitable.
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Unread 09-12-2020, 10:32 AM   #40
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I have not installed a lot of tile since the end of 2010, but I have tried, through this forum and attending numerous product training sessions, to keep up. I agree with everything Jim has said. For years I used and recommended Custom's VersaBond thinset for many of my projects which included frequent use of Schluter membranes. I didn't know, at the time, that VersaBond contains no latex.

As to dry-set mortars, I invite you to review an article I wrote in 2009 concerning the use of Ditra-set," then made by Bostic. I don't know whether the product is still available or not and haven't taken the time to find out. Ditra-set was an unmodified (dry-set) mortar. It's a short piece, and I think you'll find it interesting.

https://www.johnbridge.com/product-r...ra-set-mortar/
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Unread 09-22-2020, 05:38 AM   #41
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John,

Thanks for that link, it was an interesting insight into how long some of this debate and confusion has been going on. While I trust schluter on their thinset, I just would rather give my $ to a 3rd part, like the makers of versabond or mapei. It agitates me that schluter caused this debate then provided the solution that they sell. In my mind it’s a little dubious, but I’m sure there’s good folks at schluter.

Great insight Jim, appreciate the info. Similar to johns test in his article, I’m going to take some thinsets I have laying around and do some of my own tests with the likes of Kerdi, ditra and dry time.
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Unread 09-22-2020, 07:40 AM   #42
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Oh, the confusion has been going on much longer than that. It began when Schluter built their office building at Plattsburg NY in the late 20th Century. During the course of the tile installations, which are all over the place inside and out, it was discovered that the modified thinset used between the porcelain tile and Ditra in the bathrooms had not set up after a period of two to three weeks.

I never could get anybody to tell me which product had been used, but it didn't seem to matter. They outlawed the use of all modified thinsets with their membranes.

I have many friends at Schluter, as wall as at all the major thinset producers, and I've come to believe the conflict will be with us forever.
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Unread 09-22-2020, 09:11 AM   #43
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With respect to the glass tile modified mortar test, I would have liked to see Schluter do the SAME test with their magic mortar. I also would like to see it done with a quality mortar.

I don't expect any difference.
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Unread 09-22-2020, 10:37 AM   #44
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As someone who tests mortars on a regular basis I can say often things are not as one would think and little things make a difference, sometimes a lot of difference.
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Unread 09-22-2020, 02:13 PM   #45
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Quote:
Originally Posted by Mike
With respect to the glass tile modified mortar test, I would have liked to see Schluter do the SAME test with their magic mortar. I also would like to see it done with a quality mortar.
It would likely take just as long to dry out! The issue is, how stable is the thinset before the modifier can dry out. With latex modified mortars, not until they dry. With many others, the moisture content, unless it was overwatered which presents its own issues, is almost irrelevant. Over watering any cement based product can make for a weaker bond by potentially allowing the components to stratify, and by holding the cement particles further apart as they start to cure meaning less interlocking.

The more you know, the more a smart person realizes he doesn't know! There are a lot of subtleties about how things interact. Some companies run more by marketeers may make a recommendation that an engineer could shoot many holes in. Schluter tends to be run more by engineers than sales people.
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