Can I Use Any Thin Set With Kerdi? The ICC-ES Evaluation Report On Kerdi Says You Can

[johnfrwhipple]

...Over drywall, unprimed, no mud, assuming you wait the 24-hours they recommend when doing a flood test, the sheet is adhered pretty well and probably better than with a modified. Yes, a modified has better initial tack and ultimate strength, but if it isn't embedded into the fleece well, it could easily end up being weaker than a proper dryset installed properly. And, where you're talking about TONS of pull required to break the bond with either dryset or modified, why not use a dryset? ...

Jim you don't sound very sure in your post.

"Pretty Well" "Probably better" "Could Easliy"

The problem with your claims is that for one you still have not recommended a primer for all those jobs that do get drywall compound and to date Schluter is yet to return my email.

The second big one is you have no solid test data to draw from. Who tests these products? You mention the ICC but they actually do not test the product.

You and I are just bumping heads here. We need data. We need pictures. We need a "Mad Lab Test".

I have a bunch of Laticrete 317 Floor and Wall thin-set at home and the "Ad-mix" to make it modified. I will install four samples today on my own home's drywall in my office. The office is unfinished and I have a wack of drywall here. I might even do six samples.

Sample One: Kerdi over dusty drywall no drywall compound - set with Laticrete 317 no "Ad-Mix"
Sample Two: Kerdi over clean, lightly sponged drywall (sponge with clean water) - set with Laticrete 317 no "Ad-Mix"
Sample Three: Kerdi over primed drywall - primed with Laticrete "Ad-Mix" and set with 317 mixed with "Ad-Mix"

Sample Four: Noble Seal TS over dusty drywall no drywall compound - set with Laticrete 317 no "Ad-Mix"
Sample Five: Noble Seal TS over clean, lightly primed drywall (primed with "Ad-Mix" - set with Laticrete 317 mixed with "Ad-Mix"

I'll start there Jim.

Jim to be fair how long do you want me to wait before subjecting the test samples to weight load? I will set a "Jig" over each sample and pile bricks on until we reach a failure point. I'll measure the weight of the bricks and we will have some research to go by.

I'll call the test the "DeBruycker Drywall Therory"

...Yes, a modified has better initial tack and ultimate strength, but if it isn't embedded into the fleece well, it could easily end up being weaker than a proper dryset installed properly ...

That is a great line. You should consider politics Jim if your Kerdi job goes South.

Lets flip it around. "A properly installed modified thin set application with Kerdi is most likely stronger than a Kerdi install not set properly with dry set mortar." WTF Where do you come up with these lines Jim? Are then in your training manual or is that one of CX's old lines???

Survey Update;



JW

[jadnashua]

If drywall mud getting wetted by a laytex paint/primer/thinset/whatever really caused a bond-breaker, the paint on millions of rooms would be falling off when someone rubbed against it or bumped it. Trying to minimize the possibility is a best practice issue, how important in the real world, not sure, but I'm sure the legal gurus want it. Except when you're actually trying to remove drywall mud, how often have you had it fail when paintin, or adding thinset to it? It takes a lot of water and a lot of rubbing to get it fluid enough to do anything. Thinset has little 'excess' water in it...the water that is there is chemically incorporated into the cement as it cures. If you were using a medium bed mortar you might have an issue, but it still probably wouldn't. To preclude the small possibility, a prudent practice is to mitigate problems, and Schluter recommends a primer to seal away the moisture. Best practice is to not put it there in the first place. With the cost of labor to scrub the stuff off, it might be just as cheap to just replace the stuff with virgin drywall, then you've not got the problem at all. Tear it off, screw some new stuff up, and go for it.

Nobody should be trying to do anything to dusty drywall, neither paint, nor wallpaper, nor thinset. So, trying that is just an indication of poor practices, and anything you try is open to subjective results.

If you want to determine 'ultimate' stength, then wait the industry standard for cement products - 28-days. ALL products are spec'ed at 'full' strength after curing for that timeframe. You get a fair portion after 24-hours, and more at 7-days, but full strength is 28-days. In fact, cement products continue to get stronger the longer they cure. And, the bond between a waterproof membrane and a nearly impervious tile will achieve the full-rated strength more often with a dryset than with a modified that has trouble drying. Given enough time without stress loads, it might reach full strength. If you're talking about bond breakers, a modified over a waterproof membrane and a good porcelain large format tile, now you've got one if it is distrubed, as it needs to dry, and that can literally take more than the spec'ed 28-days.

[johnfrwhipple]

I have some pictures of the Latex Primer testing I'm doing here in North Vancouver.

I started a Blog Post so I can keep all the info in one spot here on Terry's Site.

Check it out.


Which Latex Primer is best for Kerdi over drywall compound?

http://www.terrylove.com/forums/entr...i-installation

Jim did you see my videos! I love You Tube.

[johnfrwhipple]

Jim I see you asked on the John Bridge tile forum for me http://www.johnbridge.com/vbulletin/...ad.php?t=98152 Thanks.

Too bad none of your regular buddies know the answer??? Weird. Not even John Bridge seams to know. Not even the Bird Guy XC.

You should tell Paul from Cabot and Rowe that Paint Primers are not what Dale recommended to me. I do like the reference to cutting the Ad-Mix the Grani was defantently to thick for my test.

Thanks for your help Jim. Have you tried Private Messaging John Bridge this question?

What about Bob the engineer?




Click this picture to read my Blog Post and see all the testing pictures and video.


In a week you would think one Kerdi expert anywhere online could answer the question of

"What Latex Primer is allowed to be used over drywall compound for a Kerdi installation in a shower?"

[jch]

I may be kicking the hornet's nest here, but here I go anyway....

I'm building a tiled shower in an area with a sloped ceiling with rafters 24" OC. Because of this span, I was going to use 5/8" drywall + Kerdi, rather than 1/2" Cement Board + Kerdi.

The rest of the ceiling would be 5/8" drywall (again, because of the 24" span).

Questions:
- Is 1/2" Cement Board stiff enough to span 24" on a ceiling?
- Does Cement Board come in 5/8" sheets?
- How do you handle the transition from 1/2" Cement Board (to be Kerdi'd and tiled) to 5/8" drywall in the rest of the room? The transition occurs between rafters.

*This* is the reason I was planning on using 5/8" Drywall behind the Kerdi in shower area...

Any better approaches??

[jadnashua]

You'd be better served with your own new thread...

I've not seen 5/8" cbu, doesn't mean it doesn't exist. I'd not want to tile a ceiling with either with that span. Could you add some intermediate supports up there? Will there be insulation stacked on top of this as well? I'd worry about the weight of that, the board, and the tile trying to end up bowing the material which would lead to failure...not nice to have that fall! Some cbu specify the maximum spacing - you'd want to read the installation instructions very carefully to see if they'd allow it on 24" spacing on a ceiling. Then, you have to deal with your local code people.

As an aside, the title to this thread is misleading...the referenced report says to follow the manufacturer's installation instructions, and the report covers both Kerdi, Ditra, DitraXL, and Kerdiboard. Depending on what you are installing, would call for different materials suitable to what you are installing it on, and the manufacturer's instructions do not call for just 'any' thinset, only one meeting specific specifications, brand independent, for the specific material and location of that installation.

[geniescience]

.... a sloped ceiling with rafters 24" OC.
...
The rest of the ceiling would be 5/8" drywall (again, because of the 24" span).

- How do you handle the transition from 1/2" ... to 5/8" ...

*This* is the reason I was planning on using 5/8" Drywall behind the Kerdi in shower area...

Any better approaches??

Since kerdi requires thinset on both sides, why not use thinner substrate instead of the exact same thickness? I don't get it. The way you are planning it, your tile + thinset + keerdi + thinest will be thick, on a 5/8" thickness.... And this is because you want it to line up?? Btw, what are you planning to do at the end, use a Schluter profile, or a special tile, or nothing?

In any case, I would make it all 12" between ceiling support members. Easy as pie. HAve you called the gypsum manufacturer to see if even 5/8" drywall will be warranteed hanging from studs 24" apart ??

[chefwong]

Hi John -

Love to see some updates on the testing progression.
I stumbled across this thread in research....or whether I'm going to use Kerdi or Liquid for my next project.
Regardless, it would have been CBU for the wetwalls. It's just a lil more dust to hang the boards and more heft lugging it up a flight of stairs, but the labors all the same to me.

Any reason not to post this same Topic of Discussion over at the JB Pro Forum....

[johnfrwhipple]

The test boards I made are two small.

I have started a new larger board in thew shop which is still drying out. I found that you can even install Kerdi and Noble TS with just drywall compound!

It is very interesting how long they are taking to cure. This slow cure rate part of the reason for Schluter's stand on non-modifed thin sets.

I'm trying to source the chemical that turns from blue or pink to white once dry. I would like to measure the cure times of the different modified thin sets versus a dry-set.

I'll snap a picture of my new test board today and post it.

I have four separate test under go as we speak. This weekend we are Hoarding my back deck so we can tile in the cold.

JW

[johnfrwhipple]

Hi John -

Love to see some updates on the testing progression.
I stumbled across this thread in research....or whether I'm going to use Kerdi or Liquid for my next project.
Regardless, it would have been CBU for the wetwalls. It's just a lil more dust to hang the boards and more heft lugging it up a flight of stairs, but the labors all the same to me.

Any reason not to post this same Topic of Discussion over at the JB Pro Forum....

I do not write on the John Bridge forum anymore. I prefer posting here and on Contractor Talk - less editing, less thread removals, less thread splitting and more opinions than one common Orange Theme.

I would love someone to post these same topics on the John Bridge forum. You would be surprised at how little the main contributors will contribute. You will also be surprised that information that is contrary to Schluter's advice will be posted and then confirmed many times by the regulars.

"A little birdy told me" - that's my favourite tag line.

Why don't you start a new thread on John Bridge's site and see how it goes. Post a link here so we can look at the advice you are given. It is important to check in often because so much editing happens over there. I have seen whole posts get deleted and entire threads removed.

[chefwong]

A thought did come to me when I was reading the new test thread.
Assuming that pink to white means dry. What if the chemical that makes it so dissolves due to evaporation/air.

Have you done a control sample of just dried compound and then wet it again to indeed confirm it will turn back pink/blue in the prescense of water.

I'm not on the forums that much to notice the editing....
The only thing that is a peeve is the *project* biased single thread when oftentimes, for me at least, the questions for me are more general knowledge, underlying foundation stuff while pertinent to ~the project~ but moreso a general knowledge question. A general knowledge question with a good subject title to boot -- to possibly get more eyes on the subject, oftentimes may get moved back into my project thread only to not have a single eye on it since the title thread is not relevant to the new question I was asking.

Here's a recent project of mine......I was hoping alot more pro's would give their feedback (whether positive or negative) but none of the regulars seem to care for the thread...

http://www.johnbridge.com/vbulletin/...t=97112&page=6

[chefwong]

BTW, on your notation of adhesion and Kerdi, Noble....and I'm sure you know this....but JC has glue/adhesives in it...
GP obviously has more than a topping compound, but nontheless, I'm not surprised Kerdi/Noble will stick to JC....

[geniescience]

I.... less editing, less thread removals, less thread splitting and more opinions than one common Orange Theme.

I would love someone to post these same topics on the John Bridge forum. You would be surprised at how little the main contributors will contribute. You will also be surprised that information that is contrary to Schluter's advice will be posted and then confirmed many times by the regulars.
....
because so much editing happens over there. I have seen whole posts get deleted and entire threads removed.

It's worse than that. John W is being very soft in his criticism.
They are willing to steer someone the wrong way in order to protect their sponsor membrane.

[chefwong]

JW or GS. PM me on the details on the remarks on JB.
Or just post the info here.
It's disconcerting if the information / advice being given may be biased if not wrong !

[geniescience]

if it all comes out into the open, ultimately it will put Terry Love under a lot of pressure to delete it; i.e. "cease and desist".

Just double check with the manufacturers of the products you are considering. Don't overthink things.


There are millions of membraned showers that were made with products other than the orange membrane that is all over the internet. Lots of membrane products have been manufactured, distributed, bought and sold, installed and warrantee'd, and I mean products that are not made by the one big sponsor of that friendly tile site.