A ditra question or two [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile

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Tilehelperdan
10-27-2009, 06:01 PM
So the other day I was talking to one of my suppliers when he brought up a question that I had no idea how to answer. Ok, say your doing a job over ditra. You lay it out, mud it down and snap your lines then start setting. After a while the thinset under the ditra starts to set up while your working on it. So the mud is half set, hard but fragile. His question was wether or not it is possible to break the bond between the subfloor and the scrim on the ditra. I was unable to dismiss it offhand, so im throwing it to you guys.

Question 2- Please agree with me that when installing ditra it is improper to use a 3/8" trowel and force thinset through the scrim into the areas between the cutback cavities. I tried to explain this to a setter and he called me dumb, saying it was impossible for the scrim to be enough to bond it. I told him what he made was a slab on top of the slab, and the ditra was reduced to expensive plastic imbedded in the thinset.

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Timalev
10-27-2009, 07:22 PM
You're right Dan. All you need is a Ditra trowel or at most a 1/4" x 1/4" at a 45 deg. to get the fleece to bond with the subfloor.

I think Schluter recommends you get off the floor for the normal curing period of the mortar underneath or set the next day. I would set tile over it no more than 2 hours after I set the Ditra down.

Jaz
10-27-2009, 07:51 PM
The official proper trowel for Ditra is 11/64 V or just under 5/16 V. A regular 1/4x1/4 is too much. Some use a well worn 1/4 though.

You can start setting tiles over Ditra right away. Setting tile and normal installer traffic will not de-bond Ditra. I think it's because Ditra will absorb the shock of walking on it.

Jaz

Brian in San Diego
10-27-2009, 07:52 PM
Dan,

Regarding your first question...I don't think you are going to be putting any lateral movement on the Ditra sufficient enough to disturb the bond. Light foot traffic above shouldn't hurt it either. Depending on the situation I think I would set the Ditra and start filling waffles. Come back the next day and snapping chalk lines is a whole lot easier. If you are going to line out Ditra I think you either need an ink line or you will need to use a Sharpie. Having trouble thinking that the chalk would be effective on Ditra. But I could be wrong.

I think I used a 5/16" v-notch to set my Ditra on both plywood and concrete substrates. You don't want a lot of thinset under there. You want enough to get 100% coverage but want the scrim in contact with the substrate not laying on a bed of thinset.

Brian

Saldibs
10-27-2009, 08:10 PM
Dan, I have been using Ditra for a number of years now and the only problem that I have run into that will pull the ditra off the subfloor is when you try to lift a tile off freshly set Ditra . They showed us how to do that by using a margin trowel and sliding the tile to break the bond rather than lifting. And as far as question 2 goes you are absolutely right forcing the thinset through the scrim would nullify the whole concept of Ditra. Just go watch their video to refresh your understanding of how it works.

MNTileGuy
10-27-2009, 08:22 PM
How does it feel helper Dan knowing you have a better grasp on the products you're using than the installers.

Gotta give you a :bang: feeling, eh? :D

Bellsfloors
10-27-2009, 08:23 PM
I have installed over freshly laid Ditra and also waiting till the next day. I prefer to install the first day and install tile the next day unless it is just a small project I would like to complete. I don't have the official laboratory testing but I have always felt that just the constant foot traffic could possibly deteriorate the strength of the uncured semi-set thinset. Also depending on if Modified or unmodified are concerned the bond could also be weakened (unmodified the most compromised since the adhesiveness would be less).

Also if you have to remove a tile from the Ditra before the thinset is cured. The mere suction of the tile in thinset is enough to seperate the Ditra from the substrate. You would have to remove the Ditra to respread fresh thinset since the semicured thinset won't rebond to itself after the initial set. This would be further complicated if you were using Ditra as a waterproofer also.

As to the trowel, I have found that a 3/16" x 3/16" square notch trowel works well with a properly mixed batch of thinset.

JimmyJohn
10-27-2009, 08:31 PM
I've never used any of the schluter systems before and haven't heard so much about it until visiting this site. Always been a hardibacker/durock guy...couple additional questions. Really use non-modified to bond the tile to the standard substrate schluter?? If you can lay the schluter out square in a room, do you need to chalk lines or can you go off the little grid squares???

Bellsfloors
10-27-2009, 08:41 PM
Ditra to concrete use Premium Unmodified

Ditra to exterior grade Ply use Modified

All tile to Ditra membrane use Premium Unmodified

I always use my own lines and don't rely on the squares no matter how close they look.

Splinter
10-27-2009, 08:41 PM
I wouldnt trust the little squares to be... well... square. I've stretched, tweaked, moved the Ditra a little while pushing the wood float over it to bed it into the thinset...

Tilehelperdan
10-27-2009, 08:57 PM
How does it feel helper Dan knowing you have a better grasp on the products you're using than the installers.

Gotta give you a feeling, eh?

Hit the nail on the head, Brad. Trying to explain it to him was useless. Like tits on a hog, I tell ya. :suspect:

MNTileGuy
10-27-2009, 09:05 PM
...and to top it off they're a bunch of miserly bastards! :rofl:

The quote from schluterville none of us will ever forget.:D

Ok back to your regularly scheduled program...

Tiletim
10-27-2009, 10:13 PM
...and to top it off they're a bunch of miserly bastards!

The look on Andy's face - priceless

didn't do the quote thing right did I

cx
10-27-2009, 10:29 PM
The official proper trowel for Ditra is 11/64 V or just under 5/16 V.That O-fficial trowel I got for Ditra is a square notch of that size, Jaz, not a vee.

Gotta be right on accounta says Schluter right on it, non? :Ddidn't do the quote thing right did I No, Tim, you didn't. But I done fixed it for you. :)

Gotta pewt the quotee's name immediately after an = sign, which must be immediately after the "quote" in the first set of brackets. No spaces.

Try again, eh? :)

Tiletim
10-27-2009, 10:35 PM
ok how is this

...and to top it off they're a bunch of miserly bastards! =THD

Tiletim
10-27-2009, 10:36 PM
i'm tired try this again

...and to top it off they're a bunch of miserly bastards! =THD

Tiletim
10-27-2009, 10:38 PM
3 times a charm

...and to top it off they're a bunch of miserly bastards!

Tilehelperdan
10-28-2009, 06:08 AM
What can I say. I speak the only the truth. :rofl:


Glad you figured out the quote thingy, Tim. I was proud the first time I did it right. :D

JimmyJohn
10-28-2009, 07:22 AM
Thanks to all...Ima have to give it a try one of these days as much as I hear everyone here swearin by it and not at it

Saldibs
10-28-2009, 01:38 PM
Gotta pewt the quotee's name immediately after an = sign, which must be immediately after the "quote" in the first set of brackets. No spaces.

Saldibs
10-28-2009, 01:39 PM
Just trying the quote thing it to see if I understood, I guess I got it right

cx
10-28-2009, 02:29 PM
Yup, you got it, Sal. :)

John Bridge
10-28-2009, 03:07 PM
Hi Jeff, :)

I just want to say that I can guaranty you the little squares are not lined up perfectly. I've seen the odd one here and there at about a thirty degree angle to the grid. :)