Ditra application on gypcrete [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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08-12-2004, 01:39 PM
We have decided to listen and install ditra on our gypcrete to make the tile last as long as the balance of the house! My question is, do I just use standard thinset under the ditra to bond it to the gypcrete (thermafloor)? When I install the tile, use the same? What would be the recommendation for notch size for both locations? The tile to be installed on top is either a 12"x12" or 13"x13" (approx).



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08-12-2004, 01:45 PM

pages 10 and 12

08-12-2004, 02:50 PM
It calls for "Unmodified" thinset mortar...I have always been told to use latex modified for tile...no exceptions. Is this what you pros recommend?

Thanks for the link!

08-12-2004, 02:59 PM
to see what the pros think go here : http://www.johnbridge.com/vbulletin/showthread.php?t=14549

This seems to be one area where they don't all agree. For what its worth I used Mapei Ultra Flex II (modified) to put the ditra down and for the porcelain tile that I used. We changed our minds on small area after putting down the Ditra and decided to go with hardwood. The Ditra stuck down with the modified thin set was not easy to get up and the failure was in the Ditra bond to the fleece, not in the thinset.

08-13-2004, 03:37 AM

You are using Maxxon's Thermafloor. I have it installed as well.
First thing to do is to call the installer and get some Maxxon Overspray. It is basically concentrated latex that you will water down 4 to 1 if I recall. You will roll the latex/water mixture onto the gypcrete where ever you plan on installing Ditra. The purpose of the mixture is to seal the gypcrete so that gypcrete does not absorb all of the moisture out of the thinset.

The Ditra installation handbook recommends using unmodified thinset to attach the Ditra to the gypcrete. Thats what I did and it appears to work. One suggestion is to use a gray thinset under the Ditra and not white. You will then be able to see how your coverage is.

I still have two bathroom floors, and a mud room and then I am done.

08-13-2004, 09:05 AM
Sounds good. I do have the overspray already, mainly because we are living in the house for 2 months before putting the finishes on the floor. It helps keep the dust down too.

I will order my ditra now! Thanks for the help!

Peter, what notch trowel did you use under the ditra, with the grey thinset?

08-13-2004, 09:18 AM
Hmmmm, 3/16 x 1/4 V-notch trowel if I remember correctly. I am positive that its a V-notch but the dimensions escape me. Check the Schluter site or when you order the Ditra from David Taylor ask him.

David Taylor
08-16-2004, 03:38 AM
Yes, the trowel should be 3/16" x 1/4". Over Gypcrete, the thinset should always be unmodified, including where you're going to be seaming Ditra with Kerdi-band.

It's also known as an A-6 trowel and they're available at HD or Lowes for $7-10.

While you're there, maybe check out a new BBQ. Didn't you say you'd need one after all this work? :D

08-16-2004, 04:25 PM
Oh, I need to seam the ditra with kerdi band? I was under the impression I wouldn't need to do that since I am only using it for an anti-fracture, and not water proofing. Guess I need to order some. Is it necessary?

David Taylor
08-16-2004, 05:15 PM
No, it's not necessary if you're only using Ditra for uncoupling.

Kitchen, bathroom and entrance areas are good places to make it waterproof.

08-16-2004, 05:19 PM
Hi Daniel,
I think David was speaking in general terms, if you were going to use Kerdi band. You don't need it for just antifracture.
Hi David, welcome back. Glad to see you on the boards again. :)

David Taylor
08-16-2004, 05:27 PM
Thanks, Tom - I'm glad to be back.

Now if only I could get off the road and sleep in a bed that doesn't have mints on the pillows. :)