Ditra leaves floor uneven

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  #1  
Old 05-30-13, 09:48 AM
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Ditra leaves floor uneven

I'm retiling my small bathroom, 5'x10' with 12"x24" floor tiles. I believe I laid down the Ditra correctly:
  1. 3/4" t&g plywood subfloor over joists
  2. modified thinset
  3. Ditra
  4. unmodified thinset
  5. 12"x24" floor tiles
Due to it getting late, I let the layer of Ditra over modified thinset dry over night.
The next day I began laying tile and noticed that the Ditra was very uneven in some places (1/8"-1/4" hill or valley in a 1 sqft area), most likely from the spots where my knees left impressions as I was pressing the Ditra into the modified thinset.

So, did I do something wrong? How are you suppose to keep the Ditra flat when you have to be on your knees to press it into the thinset? That's how they do it on the videos.

Thanks.
 
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  #2  
Old 05-31-13, 09:29 AM
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What size trowel did you use? I cannot imagine 1/4" high spots. With proper trowel and installation, the ditra will folllow the contour of the subfloor. Was the subfloor dead flat before you installed the ditra?
 
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Old 05-31-13, 07:54 PM
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Couldn't find Ditra trowel

Ditra recommends a 1/4"x3/16" v-trowel (or 5/16" v-trowel). The best I could find was a 1/4"x1/4" square trowel.

The 3/4" plywood subfloor didn't have divots in it, but I'm not sure that it was dead flat.

Was the trowel size my problem?
 
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Old 06-02-13, 05:34 AM
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Could be. thats a lot more thinset than Schluter recommends.
 
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Old 06-04-13, 10:20 PM
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That trowel will leave about 2x the correct amount of thin set. But that still can not account for the problem you described. Maybe you're exaggerating a bit? There is no way your knees cause a 1/8-1/4" divot. The stuff is only 1/8" total. Did you use a wooden float to press Ditra into the thin set? Didn't you back out as you worked?

I think the floor was not flat and those big tiles are giving you problems.

Jaz
 
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