We are trying to lay slate tile in an entryway. We just read the article in Fine Homebuilding No. 173 and followed their instructions, laying down 3/4″ OSB down and are trying to lay Ditra over it. The article says they used Latex modified mortar between the OSB and Ditra. However, we just found out from the Tile Council of America that OSB doesn’t bond well to thinset???? Anyone have any experience with this? Did the article get this detail grotesquely wrong?
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What about if you prime/seal the osb first. That will eliminate/slow down the loss of moisture from the mortar.
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Is there a product you would recommend? We are very concerned about any moisture at all getting into the OSB.
PVA white glue, Acryl 60, weldwood,... the list goes on and one.Any tile supplier will have something.
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"Did the article get this detail grotesquely wrong?"
Possibly. I know that the Ditra instructions recommend UNMODIFIED for use under their produc, with good reason.
As far as bonding goes, no sweat. I would just prime with a latrex bonding agent, let it dry 'till tacky and go for it.
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Taunton University of Knowledge FHB Campus at Breaktime.
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Ditra allows modified thinset to lay the Ditra down, but requires unmodified TS when setting the tile on the Ditra."I am the master of my fate, I am the captain of my soul." Invictus, by Henley.
What they allow and what they recommend are two different things. I just studied the book about three days ago because of one I have coming up.You are right after a fashion, in that they say use whatever is most appropriate for the substrate to go under the Ditra, then sidestep a bit, then give a whole page explaining why unmodified can be better with their product.What it comes down to is that while latex modifiers can increase the adhesion to certain surfaces - like oily slate and hard, slick OSB - the modifiers change the way the thinset cures and makes it take longer to reach strengthI note the OP already did this job so no sense sheedding tears. They are OK as long as they aren't rolling a piano over it this month.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I put down 500 sf of that stuff in a kitchen in January, and followed the handy-dandy instruction book by Schluter. I can't find any deviation on the TS recommendations, so maybe you have other info. Doesn't matter, though. J. Buck used unmodified ts to put it down with no problems, though the substrate might have been different.
If only it wasn't so expensive.
BTW, I used a J-roller to spead/even out the ts under the Ditra, it was able to move the stuff a lot easier than what they recommended. Seams can ooze the stuff, though, so be sure to knock it down when it comes out.
Have fun.
"I am the master of my fate, I am the captain of my soul." Invictus, by Henley.
I'm of the opinion now that I'll use what's best for the stick with the subfloor.
I've used both modified and un ... haven't noticed any difference.
a buddy said J Bridges is now saying he uses modified on top and underneath too.
from what I first gathered ... the problem was with grout cracking.
the modified cured differently ... (or was it the unmodified?) ...
and since the plastic did absorb any moisture .... it did cure as quick ...
and the "excess" moisture could screw up the grout.
I do have a big ditra job coming up ... so I gotta go read what J Bridges said ...
maybe rethink things?
even if unmodified is recommended on top ... for hard to stick tiles I'll still go with modified ... for fairly basic ceramic ... stuff that'll stick just fine with unmodified ...
if that's what they want that's what I'll give them.
Personally ... unless yer grouting immediately ... I'm not so sure any of this makes a difference?
Could be 100% wrong there though ...
I'll be sure to let everyone know if/when I find out the hard way!
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
"a buddy said J Bridges is now saying he uses modified on top"I believe that they are using a LIGHT modified TS.But I don't remember the brand..
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Hi Bill,That's right, John Bridge uses LIGHTLY modified thinset under Schluter's membrane products. He uses Custom's Versabond under Kerdi without any problems. Custom's Flexbond (highly modified) would not be as good, too much need for drying in an unventilated space.Bill
Used Ditra just recently. Used unmodified as called for between ditra and tile. Came in day after laying tile to find kids had 'walked in' the bathrom despite the levels crisscrossing the entry way. Tiles moved.Went to try and pry out now unlevel tiles and 'voila', they just lifted right out. Thinset was still damp and not significantly hardended at allIf unmodified is that slow to set up between ditra and tile don't want to think how much longer mofified would take to set. Tiles were 12x12.Let's not confuse the issue with facts!
Have you looked over the Ditra website? They have a lot of detailed information there about various substrates, for example:
http://www.schluter.com/5487.aspx