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5 Boys
03-08-2005, 03:22 PM
I want to tile a small bathroom that currently has linoleum over concrete. I would like to use ditra between the ceramic and concrete. After I pull up the linoleum, is it ok to use ditra on concrete? If so, do I use a fortified mortar, like Versabond, between the two? After that, do I use an unfortified mortar, like Masterblend mixed with Acrylic Mortar Admix, between the ditra and ceramic tile?



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03-08-2005, 04:21 PM
Welcome, Michael

Yes you can use Ditra on concrete.

Yes, use a modified (fortified) thinset to set the Ditra to the concrete.

Yes, use a unmodified thinset (especially if you intend to install porcelain tiles), no, don't add the admix, that'll make modified thinset.

5 Boys
03-08-2005, 05:42 PM
Thanks for the information. I guess I just mix the masterblend with water?


03-08-2005, 06:08 PM
There are two basic ways to wind up with modified thinsets. One is to use a modified thinset with dry polymers in it (like VersaBond or FlexBond) and mix it with water. The other is to buy an unmodified thinset (like MasterBlend) and mix it with an admix (like CustomFlex or Acrylic Mortar Admix).

For unmodified thinset (also called dryset) use an unmodifed thinset mixed with water.

George K
03-08-2005, 07:05 PM
My understanding is that UNMODIFIED goes between the concrete and the DITRA. Call Schluter 1-800-472-4588

03-08-2005, 07:20 PM
It's the other way around George,modified under,un-modified over. :)

03-08-2005, 07:50 PM
Thanks jdm, I've been trying to find out what dryset is.

George K
03-08-2005, 08:22 PM

I think that is true for a wood substrate, but not concrete. Since Schluter has to warrent their product, I would make that phone call to the 800 number before putting anything, other than unmodified thin set, under their product over concrete. If you find out I am wrong, please e-mail me before I make the expensive mistake of using the wrong thin set under my DITRA.

George K
03-08-2005, 10:09 PM
This is from the Schluter DITRA installation pdf document on their web site.

Tile or stone_________________________________
Unmodified thin-set mortar_____________________
uncoupling membrane__________________________
thin-set mortar________________________________

Notice the sequence of the layers. There is a picture that goes with this, but I could not figure out how to copy it. As you can see, the requirements for concrete substrates are different from wood and other substrates. :)

5 Boys
03-09-2005, 07:52 AM

It looks like you are right, I should use unmodified on both sides of the ditra. Thanks.

Rhode Island Flooring
03-09-2005, 08:40 AM
so what is consideres unmodified? regular dryset with no enhancers? I know masterblend is a HD product right? and fortified is with dry or liquid latex? like keralastic? and you dont use modified on either side of ditra.

George K
03-09-2005, 09:42 AM
Schluter specifies an ANSI number. My guess is that you would look for that ANSI number on the thin set bag. I have not researched thin sets yet. I'm still trying to flatten my slab :) .