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Unread 06-04-2014, 03:21 PM   #1
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Join Date: Jun 2014
Location: NY
Posts: 23
Ditra over Cement Backer board

First off all, hello and thank you for such a great forum. Next allow me to apologize in advance for any ignorance or lack of knowledge I display. I certainly know what its like reading on forums as a professional (NOT TILE...haha) and shaking my head at people posting.

But with all of that said, I really enjoy this forum. I have been reading on here for a few weeks on random points while I have been preparing to redo my bathroom. I am posting this topic, because some of the searches I came up with that addressed this were much older or had conflicting answers in the thread. If I annoy anyone with the repetition, I sincerely apologize.

So I have a 3/4 inch plank style subfloor laid on a diagonal. When we were down to the subfloor I changed some rotten planks out as a result of previous water damage, rescrewed any boards that were questionable and added wood bracing in between the joists from the basement in any spots that had too much bounce in them (bounce from the planks not from joists). I then used the flexbond thinset on the back of the cement board and screwed down the 1/2" cement backerboard on the floor.

I know this doesn't help with strength but due to the way the planks were laid it REALLY helped tie the floor in together and add rigidity to it. When I do the jump / bounce test the floor it is so rigid now (obviously non scientific). The joists were in really good condition and didn't have bounce noticeable or much deflection. It was in random plank boards where that was felt.

Anyhow that is the point I am at now (cement board thin set on top of 3/4inch plank subfloor). I purchased ditra which I intended to put down over the cement backerboard. For some reason I felt that this was another step in protecting the overall job after reading how good it was. However, after reading more, I feel like people have stated that if there is cement board down, I shouldn't add ditra on top of that.

So my question in short is should I return the Ditra or use it over the cement backerboard?

I am laying 12x24 tiles. Again thank you for entertaining my questions and sorry for any frustration in reading my post. Thanks

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