# Ditra over cutback?



## Norrrrrrrrrrrrm (Jan 20, 2007)

Hey guys,
I have a situation where I just removed 200' of cutback tile and now have the residue to deal with. I t is currently bonded to plywood and no way is it coming up, even with a thinner. I am looking to use ditra over the sub floor. I just want to make sure I use the correct thinset UNDER the ditra. After all of the researching I have been doing, it says a modified thinset is ok for this type of application. I am looking to see what others have done in this situation or any other info on this type of application.
Thanks,
Norm


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## tjbnwi (Feb 24, 2009)

Contact Mapie and Laticrete, they'll know which of their products will work if any.

Tom


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## angus242 (Oct 20, 2007)

I would do some kind of skim coat before setting Ditra. I'd be too afraid you wouldn't get decent enough coverage put Ditra straight over the uneven surface. 

There are various ways you could get a smoother finish to Ditra over and a plethora of quality thinsets that would work..


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## Builders Inc. (Feb 24, 2015)

Ardex K15 under the Ditra onto the sub floor, make sure to prime the sub floor. I used it once and it was very strong but took special tools to make it flat. I would prefer level quick and make it flat then Thinset the Ditra to that. But you have to prime surface regardless of which leveling product.


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## tjbnwi (Feb 24, 2009)

http://www.mapei.com/US-EN/Tile-&-S...Compounds,-Skimcoats-and-Additives/Planipatch

Tom


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## angus242 (Oct 20, 2007)

Depends on budget, time restraints and adjacent flooring heights. 

A pourable thinset like Ardex X78 would be perfect for skim coat over cutback. You want Ditra on as flat of a surface as possible. To stick with Schluter's silly warranty, non-modify (or rapidset) over the skim coat to install Ditra.

Because of product familiarity and discounts, I'd go over cutback with Eco Prim, Ultraplan Easy and Mapelastic CI. Tile directly over that. That is if adjacent flooring would allow.


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## Norrrrrrrrrrrrm (Jan 20, 2007)

The surfaces are quite level as is. There are a few spots from the chipping tool in the plywood I will have to spot fill to level off completely. Once the spots are filled and the thinset bed is troweled for the ditra, I will be as right as rain. I just need to make sure the thinset is the proper one. I will look on the mapei website as well for info.


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## angus242 (Oct 20, 2007)

Almost any decent modified thinset would work. For Mapei, I'd suggest Ultracontact. 

When I say smooth surface, I really mean smoooooooooooth.


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## CO762 (Feb 22, 2010)

No one has axed the most important question first:

"Norm, how can you remember how many r's are in your screen name?"


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## Norrrrrrrrrrrrm (Jan 20, 2007)

I wanted my name at least a foot long so I used 12 r's.
Thanks for noticing the elephant in the room.


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## Norrrrrrrrrrrrm (Jan 20, 2007)

Yes Angus was correct. I called Ditra and they said any modified thinset will work. Nice to be able to cross reference. Thanks for all the input everyone.


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## JazMan (Feb 16, 2007)

Why is there any question that you have to use modified thinset over wood?  But, let's go back a little.

If you removed VCT or VAT bonded with a black adhesive, it's obviously either cutback or emulsion. Since you would never install vinyl (or most anything) direct to a subfloor, I bet there's some kind of ¼" underlayment on the subfloor. If so, you need to remove that first. No more cutback.

Please confirm this so we can continue in the right direction.

Jaz


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## Norrrrrrrrrrrrm (Jan 20, 2007)

It was applied directly to 5/8 or 3/4 plywood. If were as easy as a 1/4'' or luan, it would have been removed. The reason I asked which is the suggested thinset that Ditra says to use a non coupling membrane thinset. I wanted to make sure I was reading this correctly and not putting the wrong thinset down when messing with cutback. I wanted to be clear which was acceptable under and over the Ditra.


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## tjbnwi (Feb 24, 2009)

Any thinnest is acceptable between the substrate and the Ditra. The substrate normally determines the mortar type.

Between the Ditra and tile non-modified mortar only.

Tom


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## angus242 (Oct 20, 2007)

tjbnwi said:


> Any thinnest is acceptable between the substrate and the Ditra. The substrate normally determines the mortar type.
> 
> Between the Ditra and tile non-modified mortar only.


Yes but that's when it's OK for you to be smarter than Schluter. I'm not condoning that you break their rules but Ditra is the only crack isolation membrane that I'm aware of that requires non-modified in certain circumstances. They claim air-cured thinset won't cure but Ditra does not have the highest PERM rating out there and yet, all other membranes are OK with modified. So unless Schluter uses magic to manufacture Ditra, it's more of a Schluter, cover our ass-requirement.

Once you know how and why the combo of membranes and thinsets work, you can make your own judgement on what to use.

There are no reports of any Ditra failures I'm aware of. So that means if you do have a failure, big....BIG chance it's already your fault and their warranty isn't covering you anyway. Keep that in mind.

As for going over any (non-asbestos) cutback residue, a quality modified thinset is recommended so that you actually get a bond to the substrate. A cheapo thinset might not bond.


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## Xtrememtnbiker (Jun 9, 2013)

Angus, when we took the class I asked what happens when there is a warranty claim. Cause I had the same thought, if you install everything according to their specs and there is a failure, then what...

He said they cover the entire cost of redoing the job.

He did say they had a few failures because the Ditra coming from the plant in Canada was too close to the big door and when it was really cold the fleece that's heat welded on was failing.


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## JazMan (Feb 16, 2007)

tjbnwi said:


> Any thinnest (thinset) is acceptable between the substrate and the Ditra.


Sorry Tom, but that is definitely not true. But your next statement is; Maybe you mis spoke or got confused. 



> The substrate normally determines the mortar type.


Jaz


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## angus242 (Oct 20, 2007)

Xtrememtnbiker said:


> Angus, when we took the class I asked what happens when there is a warranty claim. Cause I had the same thought, if you install everything according to their specs and there is a failure, then what...
> 
> He said they cover the entire cost of redoing the job.
> 
> He did say they had a few failures because the Ditra coming from the plant in Canada was too close to the big door and when it was really cold the fleece that's heat welded on was failing.


I mean I can't argue with what a rep told you in person. However, unless it's in writing I can't believe it. Maybe they'd cover you, maybe they won't. 

As for a true failure, I think upon investigation if they find fault in their product, the adhesive you used would be irrelevant. 

But again, it's your call if you feel following their unique requirements is for you.


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## JazMan (Feb 16, 2007)

Norm said:


> It was applied directly to 5/8 or 3/4 plywood.


Well, that's really a bad installation, but then again they were doing the job the cheapest way possible, as you know. I suggest you install some ⅜" or thicker underlayment grade ply, then Ditra.



Norm said:


> The reason I asked which is the suggested thinset that Ditra says to use a non coupling membrane thinset.


No, that's not correct. Not "non coupling", they recommend unmodified to set the tiles, but of course you have to use the mortar that is compatible with the substrate. In this case the substrate is wood, so you gotta use modified to install Ditra (or to bond anything for that matter). 

As for a failure in Ditra; That one case many years ago when the fleece delaminated on a bunch of rolls is the only thing I'm aware of. There is nothing else that could go wrong with the product.

As for warranties, I never expected to have a problem. I used a high quality modified to install the tiles for years before they came out with Ditraset in 2006. 

*** BTW, Angus, Ditra is not a crack isolation membrane. It's an uncoupling membrane. 

Jaz


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## Xtrememtnbiker (Jun 9, 2013)

angus242 said:


> I mean I can't argue with what a rep told you in person. However, unless it's in writing I can't believe it. Maybe they'd cover you, maybe they won't.
> 
> 
> 
> ...



I agree. I asked cause I was curious, but who knows what it is in writing.

So the bottom line for me is. I don't know... Schluter says use unmodified, so I'm inclined to do that. Then someone like yourself says it's fine to use modified and I'm pretty darn inclined to believe you.

So I don't know...


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