Ditra---why Or Why Not Use It?

 
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Old 02-28-2010, 05:34 PM   #1
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Ditra---why Or Why Not Use It?


I've never understood the reason to use ditra or the newer, larger ditra.
For most things, there's a trade-off and of course, other options. As contractors, we should know the "whys" of the things we do....and other options, be they better/worse/same.

So, anyone care to talk about ditra? (FWIW, if anyone want's to, they can also do similar threads with any product they like and hopefully we all can chime in there).

Pro: Lightweight.

Con: seems to eat thinset by the bags; requires two different types of thinset; hard to trowell (for me anyway), it's a barrier to the heat transfer when using radiant heat

Alternatives: easyboard, cork, denshield (never used that on floor), ?


Also, I've never understood what "uncoupling" means.
What is it?
Why do we need it?

Gratzi.
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Old 02-28-2010, 05:45 PM   #2
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Re: Ditra---why Or Why Not Use It?


Pros:

1. Waterproof
2. Lightweight
3. Much less labor to install
4. No fasteners
5. No dust
6. Easier to store
7. Easier to transport
8. Uncoupling
9. Full labor warranty (installed correctly)
10. No tools or power required to install outside of a trowel and utility knife

Cons:

1. More costly material wise than cbu
2. Requires more thinset


uncouple [ʌnˈkʌpəl]
vb
1. to disconnect or unfasten or become disconnected or unfastened
2. (tr) to set loose; release

It means that movement from the substrate will not be transferred to the tile. Cbu does not offer this due to being directly bonded to the substrate. Surely you can see the advantage of this in wood frame construction.

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Old 02-28-2010, 06:03 PM   #3
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Re: Ditra---why Or Why Not Use It?


Pro: Lightweight.
Easy to install.
Does not need expensive tools to install; no shears or saws to cut, no pneumatic nail guns or collated screws to install.
Not bulky, easy to store.
Vapor/moisture management.
Cost.
Uncoupling membrane.
Crack isolation.
Adds only 1/8" to floor height.


Con: seems to eat thinset by the bags; Not true. Uses very little more than installing CBU. I'd say no more than $20 worth of thinset over 150 sq ft. Considering there's no mechanical fasteners needed, the cost difference is most likely less.

requires two different types of thinset; Only if installing over plywood or OSB. A liquid additive used with non modified thinset not only solves that "issue" but most liquid additives are as good as modified thinsets (eg Kerabond + Keralastic)

hard to trowell (for me anyway) Using a trowel has never been an issue to me. However, you will need at least 2 different size trowels to install Ditra & then tile over it.

it's a barrier to the heat transfer when using radiant heat Not true. Polyethylene is not a good insulation material. Actually, the ribs allow for even heat distribution. Plus with all the thermal expansion/contraction going on with a heated floor, the uncoupling properties of Ditra are actually a positive.

Cannot use tiles under 2" x 2".


Also, I've never understood what "uncoupling" means.
What is it? Not chemically bonding the tile installation to the substrate
Why do we need it? Subtle horizontal movement in the subfloor can transfer to tile/grout resulting in cracked tile or grout failure. For thousands of years the uncoupling theory has been used for installations that are still intact today.
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Last edited by angus242; 02-28-2010 at 06:51 PM.
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Old 02-28-2010, 08:30 PM   #4
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by PrecisionFloors View Post
waterproof
But in order to waterproof it, don't you have to buy another product to do the seams?

Quote:
Originally Posted by PrecisionFloors View Post
uncouple [ʌnˈkʌpəl]
vb
1. to disconnect or unfasten or become disconnected or unfastened
2. (tr) to set loose; release

It means that movement from the substrate will not be transferred to the tile.
BINGO!
Thank you. I've never gotten anyone to splain that to me. I've heard it over and over, but no one has specifically said what that means.
Looking at how it was designed, the structure, I've long thought that and thus, it's use over places that shouldn't be tiled--I called it a "severe duty anti fracture membrane". And that's how I've been using it. Like I said, I use different products for the same things...but in different circumstances.

This is why I like to know or figure out the "whys" of things.

And this is why I've never understood their use on countertops.
And this is why I've told people that tiles stuck down with ditra come off easy. I've been told no, but the structure of it--uncoupling--dictates that is so. I tried to splain how when you twist a plastic glazing shim, the thinset will come off of it easily, so why not the plastic of ditra? That was a question that no one answered.

So....why wouldn't carpet glue work to bond the ditra to wood?
It sticks like the dickens.
It's more flexible than thinset--thus is retains the bond to a flexible thing (plastic).

And as ya'll can tell, I don't like unanswered questions when things point one way, but I'm lead to believe they are the other. No offense to anyone here, there or anywhere. Discussion is good.
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Old 02-28-2010, 08:35 PM   #5
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Re: Ditra---why Or Why Not Use It?


/raises hand

I have a question. Set the tile with unmodified. What about porcelain?
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Old 02-28-2010, 08:55 PM   #6
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Re: Ditra---why Or Why Not Use It?


CO, if you have demo'd Ditra installations, and it came up as easy as you say, it probably was installed using cheap thinset, or incorrectly. Why would a Ditra installation need to be torn out anyways? What were the reasons for your supposed tear outs?

Quote:
Originally Posted by CO
But in order to waterproof it, don't you have to buy another product to do the seams
So what. What do you use to waterproof your substrates? Why the aversion to multiple products?

Quote:
Originally Posted by Kyras
I have a question. Set the tile with unmodified. What about porcelain?
What about it?

Try this experiment, take a high quality unmodified thinset such as Kerabond, or Laticrete 272, or Laticrete 317, and stick two pieces of porcelain tile together. Let them set up for 24 hours, and try to pry them apart. With the unmodified thinset sandwiched between two impervious layers, the portland cement can properly hydrate, resulting in a very strong bond.

Having said that, there are some modified mortars which will work with Ditra. Unfortunately, Schluter is unwilling to condone their use in the USA at this time. This is largely a function of politics, and marketing strategy IMHO.
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Old 02-28-2010, 09:01 PM   #7
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by Kyras View Post
/raises hand

I have a question. Set the tile with unmodified. What about porcelain?
The use of modified with porcelain tile and an impermeable membrane will not properly allow the thinset to cure. Or I should say it can take, depending on conditions, the modified thinset up to 60 days to cure.

A test performed by the TCA showed that using non-modified thinset to mount porcelain tile to Ditra achieved an average shear bond strength of 190 psi OVER the minimum spec of ANSI 118.4

I make sure porcelain tile is back buttered before setting over Ditra. Also, the use of a quality non-modified with a high portland cement ratio is recommended.


EDIT: Or, use a self-curing modified thinset.
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Old 02-28-2010, 09:05 PM   #8
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by angus242 View Post
Con: seems to eat thinset by the bags; Not true. Uses very little more than installing CBU. I'd say no more than $20 worth of thinset over 150 sq ft. Considering there's no mechanical fasteners needed, the cost difference is most likely less.
Between that and the floor, it's neglible. But don't you think it takes a lot more thinset because you have to fill all those holes even before you can trowel anything down for the tile?
For troweling, I don't like the it as it's not flat. Hardi is flat, but the dryness seems to want to grab the thinset, whereas cbu is just like smearing it on, well, concrete. I think that's just a personal pref thing tho.

As far as fasteners, the thing I DON'T like about denshield is the fastening. I have to use nails and am not thrilled about that, so I sneak in a few durock screws and redguard them.

Quote:
it's a barrier to the heat transfer when using radiant heat Not true. Polyethylene is not a good insulation material. Actually, the ribs allow for even heat distribution. Plus with all the thermal expansion/contraction going on with a heated floor, the uncoupling properties of Ditra are actually a positive.


IIRC, the ribs you talk about are the high points along the "squares".
Aren't those air spaces? Air convects heat, opposed to say thinset/stone/concrete that convects it. Convecting is about a billion times more efficient. OK, exaggeration, but this is why one can measure/feel earthquakes 1/2 way around the world, why water is a better conductor of "sound", etc. On that "carpet glue" job, they wanted radiant heat under it. We said it wouldn't conduct up to the floor very good due to the ditra. (IIRC, it was new back then in the US and certainly no one here had ever dealt with it). We were pulling mfg propanda from the heat people, from schluter, etc. talking to anyone and everyone. No one had a solid solution. Some said the heat should go on top of the ditra (which we agreed with) and others said below.

IMO, the uncoupling itself doesn't lend to any for of efficient heat exchange/transfer. It'd be interesting to see some data on this, actual data. One of the things I use leftover ditra for is to keep the floor warmer than the slab, preventing/reducing eliminating convection of cold from the slab--and it works. Now I've got a bunch of bloo goo, so I'll use that for such things.

Speaking of old world stuff, does anyone even shotblast their substrate anymore if it's not broom finished? Does anyone even talk about that anymore? I know there are people that say acid etching is good enough, but it's not--it's only for thin film coatings. Even then, it's borderline.....
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Old 02-28-2010, 09:05 PM   #9
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by CO762 View Post
But in order to waterproof it, don't you have to buy another product to do the seams?

Yes you do, Kerdi band.


So....why wouldn't carpet glue work to bond the ditra to wood?
It sticks like the dickens.
It's more flexible than thinset--thus is retains the bond to a flexible thing (plastic).

I honestly can't say it wouldn't work. I do know you're on your own as far as a warranty is concerned. I usually don't question the guys that designed it in the first place, and have waaaaay deeper pockets for R&D then I do lol.

And as ya'll can tell, I don't like unanswered questions when things point one way, but I'm lead to believe they are the other. No offense to anyone here, there or anywhere. Discussion is good.
Quote:
Originally Posted by Kyras View Post
/raises hand

I have a question. Set the tile with unmodified. What about porcelain?
That has been a question for many Kyras, myself included. Again I refer to the people who have done the R&D. I do know why they require dryset. Highly modified thinsets require air to cure, or at the very least a much longer cure time, that Schluter knows most will not give before grouting. I personally have had NO issues using modifieds with Ditra or Kerdi. I also use good sense when it comes to cure times. I have installed a lot of large format porcelain over both with zero bonding issues.
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Old 02-28-2010, 09:22 PM   #10
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by HS345 View Post
Why would a Ditra installation need to be torn out anyways? What were the reasons for your supposed tear outs?
Actually, I'm making all this up because I have nothing better to do....

The ditra tearouts I've done have been for repairs and changes. The best one was when the "designers" (the money people) came in and saw how dark it was and we had to demo the whole unit. Turned out the designers were telling the architect what to do. Or mebbe.....

Quote:
What do you use to waterproof your substrates? Why the aversion to multiple products?
Depends upon what it is...and if there's a need to. Shower/tub walls, I rarely did, but sometimes I'd do a foot off the bottom. why I have no idea. Must have been bored. Horizontals and joints I usually did 9235 because I always had some of that on hand. Later, I started using redguard as the HO would buy it and they were in small jobs.
I'm out of black stuff, have a boatload of blue stuff and no red stuff.
I do have some carpet glue tho.

One used to be able to buy ditra off the roll at the local HD. Not no mo.
Now they sell rolls. And I don't think they sell kerdi for the joints. Might have to break out the redguard and drywall tape.....
Another negative I forgot to mention about a schluter product--availability.
But on the bright side, they're turning out installers/distributors by the boatload.

Seriously, if I wanted waterproofing, that meant horizontal and ditra would be right down there with hardibacker for my preference of use.

Quote:
Having said that, there are some modified mortars which will work with Ditra. Unfortunately, Schluter is unwilling to condone their use in the USA at this time. This is largely a function of politics, and marketing strategy IMHO.
Thanks for that input. I've not got those products on hand, but there's a pallet of 255/254 that I've been thinking of using a bag to try out. I hear that 255 is a godsend, but as usual, my bud says, "I've tried them all and they all say the same thing...." that makes me want to try it all the more.....
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Old 02-28-2010, 09:25 PM   #11
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by CO
As far as fasteners, the thing I DON'T like about denshield is the fastening. I have to use nails and am not thrilled about that, so I sneak in a few durock screws and redguard them.
But wait, but wait! That's four different products you hafta buy. I thought you didn't go for that sort of thing.
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Old 02-28-2010, 09:30 PM   #12
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by CO
Thanks for that input. I've not got those products on hand, but there's a pallet of 255/254 that I've been thinking of using a bag to try out. I hear that 255 is a godsend, but as usual, my bud says, "I've tried them all and they all say the same thing...." that makes me want to try it all the more.....
Just beware, I said some, not all. 254/255 wouldn't be good choices. You want the self hydrating varieties of modifieds.
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Old 02-28-2010, 09:36 PM   #13
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by HS345 View Post
But wait, but wait! That's four different products you hafta buy. I thought you didn't go for that sort of thing.
You misunderestimated me you obama voter.

I use different products for different situations--the commonality among all of them is they are all commonly available everywhere. And most things I have in a storage unit/spare bedroom that I call "the tool room", sans the sheetstock. Well, OK, I don't think HPG is. Thank buddha 5 gal buckets can last for many "small jobs" where i'd use it.
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Old 02-28-2010, 09:40 PM   #14
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Re: Ditra---why Or Why Not Use It?


Quote:
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Just beware, I said some, not all. 254/255 wouldn't be good choices. You want the self hydrating varieties of modifieds.
OK, the just on this board I'll use that as an excuse to use 255. For me, I'd just want to see what all the hubub is about and why something should cost 30/bag. I've used mapei's ultracontact for very specific things, so i'd like to see why 255 should be used. I'm helping on a job that's winding down next week, so it may be a while before I can try that on something.
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Old 02-28-2010, 09:43 PM   #15
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by CO762 View Post
Between that and the floor, it's neglible. But don't you think it takes a lot more thinset because you have to fill all those holes even before you can trowel anything down for the tile?
You use less under but more over. Like I said, for 150 sq ft, it is about $20 of thinset more I'm using as opposed to what I'd use for the same sq ft of CBU. You'd also need about $8 worth of fasteners to screw the CBU. That means it's roughly $12 worth of "extra" thinset needed to install Ditra compared to CBU. That's not what I'd consider anywhere near a lot.
EDIT: Did I mention the cost of the alkali resistant mesh tape

I stand by my statement, polyethylene is not a good insulating material. It will not effectively stop heat from radiating through it.
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Old 02-28-2010, 09:49 PM   #16
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by Angus242
I stand by my statement, polyethylene is not a good insulating material. It will not effectively stop heat from radiating through it.
Additionally, heated floors tend to have more movement, another distinct advantage of using an uncoupling membrane in a heated tile assembly.
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Old 02-28-2010, 10:03 PM   #17
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by CO762 View Post
And this is why I've told people that tiles stuck down with ditra come off easy. I've been told no, but the structure of it--uncoupling--dictates that is so. I tried to splain how when you twist a plastic glazing shim, the thinset will come off of it easily, so why not the plastic of ditra? That was a question that no one answered.
You are correct, thinset does not stick to the plastic. That is why the cavities have a cut-back design. Once cured, the thinset is locked into the Ditra. Same concept as a dovetail joint in wood. Pretty strong joinery, no?


Quote:
Originally Posted by CO762 View Post
Discussion is good.
Well it has been pretty good for you. Seems you had some misconceptions to the overall concept of Ditra in both installation and performance.
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Old 02-28-2010, 10:05 PM   #18
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Re: Ditra---why Or Why Not Use It?


Quote:
Originally Posted by angus242 View Post
Plus with all the thermal expansion/contraction going on with a heated floor, the uncoupling properties of Ditra are actually a positive.
Quote:
Originally Posted by HS345 View Post
Additionally, heated floors tend to have more movement, another distinct advantage of using an uncoupling membrane in a heated tile assembly.
I said that but something about an earthquake came up and well.....
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Old 02-28-2010, 10:19 PM   #19
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Re: Ditra---why Or Why Not Use It?


Oops, I missed that. Shame too, 'cause you said it so much more eloquently than I did.
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Old 02-28-2010, 10:31 PM   #20
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Re: Ditra---why Or Why Not Use It?


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Oops, I missed that. Shame too, 'cause you said it so much more eloquently than I did.
Nah. But I do think we made sure the point has gotten across!!

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