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

[johnfrwhipple]

I have been looking into acceptable backer boards for shower construction and debating for the last week with Jim over on this thread.

Jim is saying that in the USA Kerdi is approved for use over drywall. I said no that it is not and later in the week called an inspector in Pittsburgh, PA who said that most single family homes are under the building code of the IRC.

Not to get side tracked here but I just download the most recent ICC report on Schluter and here is what it says.

"Installation of Schluter® - KERDI, Schluter® - DITRA and Schluter® - DITRA XL membranes and accessories must comply with this report and the manufacturer’s published installation instructions. The manufacturer’s published installation instructions must be available at the jobsite at all times during installation.
The membranes are suitable for use with any bonded, thin-set mortar without the need for additional adhesives or primers.
The membranes are separated at expansion joints to avoid restriction of the joint movement, and the seams are sealed with flexible KERDI-FLEX." * Source

The report also states this; "5.1 Installation must comply with this report, the manufacturer’s published installation instructions and the applicable code. In the event of a conflict between the manufacturer’s published installation instructions and this report, this report governs."

Now the way I read this is that now we have Ditra, Ditra XL and Kerdi classified as primary waterproofing membranes meeting ANSI 118.1. And since the report differs from Schluter's install instructions all installs and seams need to be banded with Kerdi Flex and that any thin-set mortar can be used.

Am I missing something here? The reference to not needing primers could also mean that Ditra and Ditra XL need to be set with non-modified thin set??

So who is right? The old Kerdi install instructions or the new ICC specifications. In order to obtain an IAPMO certification an ICC report is needed. This report states that if there is a difference between the manufactures printed guidelines and the ICC report that the ICC report coverns.

Weird.

And by any thin set I would assume I can use any pre-mixed modified thin set as long as I don't add any admix to the mix???

WTF!

Here is a link to the report - http://www.icc-es.org/reports/pdf_fi...S/ESR-2467.pdf

This can not be right. How could the ICC screw up so badly? Or is Schluter opening the door to a wider setting material selection? I heard from the sales girl at Golden Flooring that they where working on just that. Maybe this is the way to do it.

If you follow the install specs on Schluter's website you are technically installing Kerdi and Ditra wrong if you do not use the kerdi flex for the seams. I can not wait to hear what the proper answer is.

Just when I thought I understood the process it appears it's changing.

Come on Jim - get up. This question is right up your alley!

[BobL43]

does this qualify as a conundrum or a dilemma?

[johnfrwhipple]

does this qualify as a conundrum or a dilemma?

I got Eric from Noble company shedding some good light onto the problem over on Contractor Talk. Eric mentions that drywall was removed from the TCNA book years ago so I guess we know Jim's copy is outdated and Eric also mentioned that you can get what ever kind of report you want but the code is the code and with TCNA, ANSI and TTMAC drywall is not listed.

That is not what bugs me. What bugs me is do I use regular non-modifed thinset to install ditra on plywood or can I use any thinset for ditra or Kerdi. And further more do I need to use the Kerdi Flex to seam my Kerdi sheets. We always use Kerdi Band or scraps of Kerdi or overlap the Kerdi itself.

Crazy that the ICC rules need to be followed verses the Schluter rules.

"
Installation must comply with this report, the manufacturer’s published installation instructions and the applicable code. In the event of a conflict between the manufacturer’s published installation instructions and this report, this report governs." * Source

http://www.icc-es.org/reports/pdf_fi...S/ESR-2467.pdf

Jim should know - they must discuss this at the lunch table

I started testing latex primers that might work well with drywall compound. It's been over a week and I have not been given any product to use.


JW

[BobL43]

I got Eric from Noble company shedding some good light onto the problem over on Contractor Talk. Eric mentions that drywall was removed from the TCNA book years ago so I guess we know Jim's copy is outdated and Eric also mentioned that you can get what ever kind of report you want but the code is the code and with TCNA, ANSI and TTMAC drywall is not listed.

That is not what bugs me. What bugs me is do I use regular non-modifed thinset to install ditra on plywood or can I use any thinset for ditra or Kerdi. And further more do I need to use the Kerdi Flex to seam my Kerdi sheets. We always use Kerdi Band or scraps of Kerdi or overlap the Kerdi itself.

Crazy that the ICC rules need to be followed verses the Schluter rules.

http://www.icc-es.org/reports/pdf_fi...S/ESR-2467.pdf

Jim should know - they must discuss this at the lunch table

JW

I'm still trying to decide which matting to use; Ditra, Spider Web or the Noble Seal TS. I thought that modified, like Versabond was fine to use to bond the Ditra to plywood. According to what you just wrote, that is up in the air now too? One you did not mention (for tiling over plywood) is Tavy thin skin and his glue. Would you rather me start another thread on that?

[jadnashua]

The installation instructions are referenced and cover this.

Bonding Ditra or DitraXL is dependent on the substrate it is going over: they call out modified to bond it to a wooden subfloor and (I think, I'd have to reread the manual, either modified or) unmodified over masonary materials...it's pretty clear. Since Ditra is only spec'ed for floors, and the deflection issues and movement issues with wood are the biggest unknown, the use of a modified is called for, espcially since there's a moisture release path, both through the substrate and by the open channels of the membrane itself, out to the sides.

They call for unmodified when installing Kerdi, both under and over, and unmodified on Ditra over as there's no good moisture migration path between the tile and the waterproof membrane.

If you want to deviate from this, they say you need to call both them and the material (likely tile) manufacturer to come up with a suitable solution, if there is one. I have heard, indirectly, that they've allowed a rapid set modified when asked. Rapid set mortars are not likely a good solution for a DIY'er because of the limited pot life.

IF you want Ditra or Dita XL to be waterproof, then you need to band the seams, just like you do with Kerdi and that calls for an unmodified, since it is on top of the membrane. This may call for two different thinsets, or the same one and mixing it with either water or their addative to make it into a modified (probably the simplest since you don't have extra thinset in the wrong configuration - you make it up to need as required).

This is all called out in the manual. The key is: suitable and per the manufacturer's instructions.

[johnfrwhipple]

Jim I just got off the phone with Woody at the ICC. Woody tells me that any deviation from the ICC report will net a build not to code since it does not follow the ICC instructions.

The process goes like this.

Schluter puts together a system and has it privaetly tested. Then they send the test results to the ICC. Then the ICC writes up the procedure based on the private test.

The ICC is clear that the instructions must be followed.

"
Installation must comply with this report, the manufacturer’s published installation instructions and the applicable code. In the event of a conflict between the manufacturer’s published installation instructions and this report, this report governs." * Source

http://www.icc-es.org/reports/pdf_fi...S/ESR-2467.pdf

Do you find it odd like me that Schluter choose to use Kerdi-Flex for the test? Did you know that Kerdi Flex is 12mil thick? Kerdi is 8mil and Kerdi band 4mil.

The ICC report also states that seams need to be banded with Kerdi Flex, not Kerdi and not Kerdi Band.

In Europe this Kerdi Flex is used in showers with Kerdi DS the 20mil version of Kerdi.

Jim you posted the information and now you choose to stay neutral. Surely the ICC report is right. And the report is not something they even test - they just write it up.

So to get back to your discussion about drywall.

If you use drywall and Kerdi and then seam your sheets of Kerdi with Kerdi - Flex your good to go. That is the proper procedure.

Thanks for the information Jim.

JW

[BobL43]

The installation instructions are referenced and cover this.

Bonding Ditra or DitraXL is dependent on the substrate it is going over: they call out modified to bond it to a wooden subfloor and (I think, I'd have to reread the manual, either modified or) unmodified over masonary materials...it's pretty clear. Since Ditra is only spec'ed for floors, and the deflection issues and movement issues with wood are the biggest unknown, the use of a modified is called for, espcially since there's a moisture release path, both through the substrate and by the open channels of the membrane itself, out to the sides.

They call for unmodified when installing Kerdi, both under and over, and unmodified on Ditra over as there's no good moisture migration path between the tile and the waterproof membrane.

If you want to deviate from this, they say you need to call both them and the material (likely tile) manufacturer to come up with a suitable solution, if there is one. I have heard, indirectly, that they've allowed a rapid set modified when asked. Rapid set mortars are not likely a good solution for a DIY'er because of the limited pot life.

IF you want Ditra or Dita XL to be waterproof, then you need to band the seams, just like you do with Kerdi and that calls for an unmodified, since it is on top of the membrane. This may call for two different thinsets, or the same one and mixing it with either water or their addative to make it into a modified (probably the simplest since you don't have extra thinset in the wrong configuration - you make it up to need as required).

This is all called out in the manual. The key is: suitable and per the manufacturer's instructions.

Thanks Jim, I did download and read the manual a few weeks ago, but can't seem to remember anything about using their own additive. going to re-read it again. This sounds like more art than the science it should be to me. And maybe that art is in the form of BS

[johnfrwhipple]

Jim what edition is your IRC Code Book and TCNA?

I think you have copies that are at least 10 years old.

I heard again from another industry insider who said the TCNA removed drywall ages ago and likewise even the Gypsum industry does not want their product in showers.

I think you need to update these manuals or at least get your information from someone who still works in the business.

Just saying.



JW

[jadnashua]

John, you're not interpreting it correctly. They state: 'The membranes are separated at expansion joints to avoid restriction of the joint movement, and the seams are sealed with flexible KERDI-FLEX.'

Got a crack in the floor? Need to keep it waterproof? Butt the DITRA seams and seal it with KERDI-FLEX. Build a shower: read section 3.4.1 again...it calls out Kerdi-Band for waterproofing the seams.

Determine acceptable backer boards? Read section 2.0, it lists gypsum board. This is from August 2011, not old, although they also did a test on it a long time ago. The test reports are not valid forever.

[jadnashua]

Thanks Jim, I did download and read the manual a few weeks ago, but can't seem to remember anything about using their own additive. going to re-read it again. This sounds like more art than the science it should be to me. And maybe that art is in the form of BS

Most thinset manufacturers offer an addative that can be used with their dryset (unmodified) thinsets. WHen you use this addative, it essentially becomes a modified thinset. You use that instead of water when mixing the thinset up. It is not a Schluter thing...it is entirely a thinset manufactuer thing. If your job might require both types, you can stock up on the unmodified and the addative, then, by choosing how you mix it (add water for unmodified or the addative/admix) and you get a modified). This can simplify things for you. There's nothing in the Schluter installation manuals about this, they only state what type to use, not how you obtain it.

[johnfrwhipple]

John, you're not interpreting it correctly. They state: 'The membranes are separated at expansion joints to avoid restriction of the joint movement, and the seams are sealed with flexible KERDI-FLEX.'

Got a crack in the floor? Need to keep it waterproof? Butt the DITRA seams and seal it with KERDI-FLEX. Build a shower: read section 3.4.1 again...it calls out Kerdi-Band for waterproofing the seams.

Determine acceptable backer boards? Read section 2.0, it lists gypsum board. This is from August 2011, not old, although they also did a test on it a long time ago. The test reports are not valid forever.

Jim did you know that Kerdi Band is only 1/10 of mm in thickness or 4/1000ths of an inch? I always thought it was just Kerdi cut into small rolls. Kerdi is 8/1000ths of an inch. That is enough protection in the corners?


So Jim are you saying that Kerdi-Flex is also good for cracks?

And what about the thinset?

"4.0 INSTALLATION
Installation of Schluter® - KERDI, Schluter® - DITRA and Schluter® - DITRA XL membranes and accessories must comply with this report and the manufacturer’s published installation instructions. The manufacturer’s published installation instructions must be available at the jobsite at all times during installation.
The membranes are suitable for use with any bonded, thin-set mortar without the need for additional adhesives or primers.
The membranes are separated at expansion joints to avoid restriction of the joint movement, and the seams are sealed with flexible KERDI-FLEX." * Source

IS it OK based on the report to use any type of thinset with ditra and kerdi or only un-modified? Or does the report say to use only unmodified thinset and if that is the case what about Ditra over plywood? The report does not list or recommend modified or un-modified. They state "Any Bonded Thin-set." What does that mean?

You mention the report like the ICC did testing on it - they did not, the ICC simple uploaded the testing results Schluter had done elsewhere.

The ICC is not a building code I'm told but the procedures in them must be followed as they are the ones the manufacture had tested.

[jadnashua]

The report specifies following the instruction manual...the manual specifically identifies which thinset is required. Unmodified for Kerdi, and surface dependent for Ditra. One thing to keep in mind with Ditra is that on the top of it, the thinset only has to hold the tile...it does not bond to the membrane, and, because it can't outgas to dry, they specify an unmodified on top. On bottom, depending on the substrate, you may have up to two paths for drying: one through the channels created by the waffles and another through the surface. The 'pillars' that form when you fill the dove-tailed waffles lock it into the membrane, and hold the tile up. The sizing of the waffles is such that to get a minimum of three pillars, you need at least a 2" tile (thus the restriction in the manual when using Ditra as to minimum tile size - the pillars form the vertical support structure).

I'll go back to my example from another time: is 1/8" glass any less waterproof than 1/2" stuff? Then, consider that it is OVERLAPPING the underlying material, so it is essentially adding to the thickness of the SYSTEM and doesn't stand alone. Kerdi installs must be taken as a SYSTEM, made up of correctly applied parts.

[mtcummins]

So to get back to your discussion about drywall.

If you use drywall and Kerdi and then seam your sheets of Kerdi with Kerdi - Flex your good to go. That is the proper procedure.

JW

Did I just hear John say that drywall in a shower is proper given a proper installation? Did hell just freeze over?

[johnfrwhipple]

Did I just hear John say that drywall in a shower is proper given a proper installation? Did hell just freeze over?

MTCummins "Hell did not freeze over" I was trying to ask Jim a question.

I was asking Jim the install process with Kerdi over drywall.

Jim what primer do you recommend to people when applying Kerdi over drywall walls that have been skimmed out with drywall compound.

Schluter is a litttle fague on this point. Can you offer up some insight for use? Perhaps you can start a thread on John Bridge's forum?

I have started some testing with Mapei's products. But while I work this out here in Vancouver what do you think I should use?

MTCummins what do you use as a latex primer with Kerdi installs over drywall?

Dale Kempster mentions using a Custom or Mapei product but does not say exactly which one? Since I do not recommend Kerdi over drywall and I do not think anyone should go this route at least for those following all these old threads where the use of drywall is actually promoted as better than CBU we should give out the best possible advice.

So boys "Which Latex Primer do you recommend over drywall compound on drywall for a Kerdi installation?"

Thanks for the help!

Merry Christmas Men - let the debates only grow in numbers in the new year. May all your tile installs be straight and true and all your showers "Water Tight"!

JW

[jadnashua]

The best thing is to not mud the walls before applying Kerdi. The thinset and the membrane works great to fill minor (nail/screw) holes and fill the tapers of the boards or joints. I'll try to get a read on what works, and if I do, I'll report back. My personal feeling is, if it is a small area, you have virgin drywall around it, and the tile is fairly large, it's not a big thing since even if the moisture from the thinset does soften the stuff, once it dries, it's good, and the whole area around it is tight in the interim. Now, on a large area like a seam, it could be a problem best averted by not mudding in the first place.

Being a holiday weekend, responses will be delayed, but I would think that this, for example would work fine: http://www.custombuildingproducts.co...er=arc&lang=en

Every thinset manufactuer sells a laytex primer for its SLC, and similar products that improves the bond and seals the underlying materials so the cement products will stick better.