JohnfrWhipple
BATHROOM DESIGN & BUILD
Can I use any thin set?
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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 Eric mentions that drywall was removed from the TCNA book years ago so I guess we know Jim's copy is outdated and Eric also mentioned that you can get what ever kind of report you want but the code is the code and with TCNA, ANSI and TTMAC drywall is not listed.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_files/ICC-ES/ESR-2467.pdf
Jim should know - they must discuss this at the lunch table
JW
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.
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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
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
This is awkward, but...
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