Help, Ditra didn't set down as intended. What to do?

enduringSeptember 27, 2012

I mixed Ditra-Set with H2O, to a what I thought was a relatively loose mixture. 1/3 of a bag with 2 quarts of H2O. I had watched the Ditra Videos ad nauseam. I let the mixture slack for 15 min then stirred briefly again. I keyed in the thin set to the surface (SLC). Then I tried to notch it with my V notch 1/4x3/16" trowel that was recommended. I noticed that there was some rubbing off of the thin set. So I tried to keep my angle bigger so I wouldn't rake it too shallow. I set the Ditra and rubbed hard all over with my grout float to set the Ditra into the thin set. I pulled up a corner and only 75% of it was in contact with thin set. I pulled it up and applied more. I finally got that area fairly well and as I continued I thought I was going to be OK. But the other end wasn't set either. I tried to add more thin set there too. I rubbed and rubbed the float with all my might. I pulled up the other end and only about 75% was in contact. Mind you this was only one 7' strip. CRAP. My thin set was getting dry. I pulled it all up and scrapped all the thin set off.


1) What did I do wrong?

2) Was I supposed to wet down my SLC so that the thin set wouldn't dry out too quickly?

3) Do I need to use a larger notched trowel?

This was supposed to be the easiest part of the tile job!

I don't suppose anyone could tell me if I can reuse the Ditra piece I washed really well. It is hanging to dry as I write this.

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Got it down on the second try :)

    Bookmark   September 28, 2012 at 8:06PM
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what did you do differently? Just wondering because we're getting ready to do our floors.. thanks!

    Bookmark   November 20, 2012 at 10:05PM
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Oh crap I can't remember :/ I will look on the john bridge forum cause I think I had posted there to to get info on this issue. I have to say washing the wet thin set off of the Ditra worked just fine. I was careful with the rubbing on the fleece side and hosed it very well. The backing was still tight. I let it dry and re-applied to the floor. I will get back to you on the project after I take a look at the JB forum. Be right back.

    Bookmark   November 20, 2012 at 10:10PM
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Well I looked on the JB forum at my post and I didn't mention this problem there. I think I may have not used enough thinset. And when I pulled it up to check I had a lot of empty spots. One thing to be sure to do is really press it in with your smooth board or what ever you use to press it down. Also be sure the thinset is spread very evenly. I had problems with a few uneven surfaces. Some areas where too high to tolerate so I went back after it was set and cut them out with a utility knife, scraped the thinset off of the floor, and cut out new patches and set them in place. I used "Ditra-Set" thinset. It is an unmodified thinset because I was going over SLC. I hear it is quite a nice thinset. If one is going over plywood I think modified is recommended but I am not sure. I followed the instructions exactly and watched the installation videos multiple times to get the feel of the whole process. I am 60 y.o. and not as strong as I used to be. This project was hard physically for me to do, so I think that accounted for the difficulties I encountered. I could hardly get the thin set stirred. It was a work out. If you guys are fairly strong and attentive you shouldn't have a problem. I can "make" things and have always been fairly competent, but it was my strength that was my downfall on this project.

    Bookmark   November 20, 2012 at 10:30PM
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Thank you for answering. I think we should be able to handle it, just very nervous trying new things and am trying to gather all the helpful notes/experiences before we start. Thanks again!

    Bookmark   November 20, 2012 at 10:50PM
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I totally relate to the nervous part. I take a long time to do things because of nerves. My DH says, "well of course it is taking time, you've never done this before". Very supportive.

Here are the steps of my floor in pictures. I know this is beyond the scope of this post but here is a summary of my floor job. I have the tiled walls to do yet, and the sink (i'm making out of soapstone), and the cabinet man to install the cabinets.

Getting the deflection corrected to accomodate stone tile. If interested in using a calculator for this go to the John Bridge forum. We added joist between existing joist. We screwed them to the subfloor on the top side every 6 inches or so. DH doing this awful job:

3/8" exterior grade filled AC (I think) plywood over 3/4" old subfloor and 3/4" fir tongue and grove. Screwed down 4"oc, though was supposed to be 6"oc, but I forgot those instructions :) so more work than needed:

One of the many steps taken to waterproof my floor in prep for SLC, it is like water and will run out of your room into the basement or where ever:

My heating wire installed. I calculated this layout almost to the last inch. That is because I drew out the layout several times to get it worked out on "paper" first (computer). I primed for SLC before I laid this out and again after the layout, being careful not to pool the primer (read that somewhere?) I also laid a plastic lath over everything and stapled it down every 4" or so, to provide strength to the SLC:

Pour SLC, have help!

Ditra down, before my patch repairs, I know you can do better than this :)


Finished floor. I used slate and Laticrete epoxy grout. Still need to caulk the threshold:

If you haven't done so search for stacyneil's bathroom and the process she documents when she did her bathroom floor and the SLC job. Very helpful.

    Bookmark   November 20, 2012 at 11:41PM
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Wow thats nice... How did you attach that plastic/foamy blue waterproofing thing to the perimeter of the bathroom?

    Bookmark   November 21, 2012 at 10:53AM
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First of all I bought the 1" thin strips of wood, and used old scraps of caulk tubes I had, to affix them to my studs for a water proof type dam, all around my room. Then I used the blue stuff to face it using a hot glue gun every so often. I used the blue stuff because I wanted to take the wood strips out so I would have a gap between the studs and the SLC for expansion of wood, as I have an all wood house. The blue stuff was so the wood wouldn't be stuck to the SLC. I don't really know if that would have stuck or not.

I can't link a JB forum site that is a tutorial for putting in heated floor and SLC because GW thinks it's spam. Here is the address www dot john bridge (alloneword) dot com

I pretty much followed this procedure but I think I did a few things different too. It is located in that forum's "Liberry" and is called "SLC & electric radiant heat". There is a ton of stuff over there. If you haven't visited it's a must. I use the same name over there. I haven't done a lot of posting there but have posted a few questions. Check it out.

    Bookmark   November 21, 2012 at 3:08PM
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