SLC between cement board and ditra

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Old 02-29-16, 01:11 PM
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SLC between cement board and ditra

Question,

I'm tiling my bathroom floor need to level the floor. The floor is 3/4 plywood with cement board (glue & screw) on top (I know, I should have done things differently, but this is a first for me - this is where it is at). I am using the Schluter Ditra Heat membrane and using self leveling compound.

So here is my question, do I [B]need[B] the primer and mesh if it is only between the Durock and Ditra Membrane?

Is there anything else that you think I should know about this step?
Thanks much!
 
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Old 02-29-16, 04:02 PM
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What glue and screw? I don't understand what that means and certainly would hope that whatever "glue" you used is rated for heat. An answer like "this is where its at" is most likely not what you want. Tile should be an install that lasts years and years. But if not done correctly, can fail in short order. First time or hundredth time you should do some research so you know what you are doing. We can help, but I have a thing about trying to correct and make adjustments for something that is wrong in the first place. Also, if using ditra heat or ditra, the cement board is not needed. Tile needs a flat surface, not necessarily a level surface.

So, lets figure out what you have, what you used so far, be specific with brand names and types.

Need to know your floor make-up, size of joists, spacing of the joists, unsupported span of the joists? Then is the 3/4" tongue and groove or not? What was the glue used on cement board? Type of screws used? and a complete description of what is wrong with the level.

Sorry for all the questions, but the goal is a successful installation.
 
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Old 03-01-16, 02:28 PM
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Indeed a lot of questions and thanks for taking the time... Had I realised... I would have skipped the cement board and shim the area of the floor which slopes. But "this is where we are at" meaning I don't want to rip up the whole floor.

floor area is approximately 7'X7', joists are 2x12, 16" on center, unsupported span is approximately 15', 3/4" is tongue and groove.

(made a bit of a mistake previously) I used Liquid Nails between the 3/4" and the joists, (don't remember which screws I used for 3/4" to joist) I actually used AcrylPro tile adhesive between Durock cement board and 3/4" and I used Durock floor screws for Durock to 3/4"

the floor is not flat. There is a significant break point between the level and not leveled section of the floor. The significant slop is in one corner of the room and the lowest point is about 3/4" off.
 
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Old 03-01-16, 03:20 PM
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Hate to be the bearer of bad news, but your AcrylPro Adhesive is not heat rated. Here is the line lifted from the spec sheet

Not for use over radiant heat systems.

Can be found in this document - http://www.custombuildingproducts.com/tds/tds-127.pdf

Either lose the heat, or tear out - let us know how you plan to proceed. I am really curious the reason for the slope in a floor whose joists are 2x12. They are usually rock solid and well within specs for span.
 
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Old 03-01-16, 04:03 PM
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Hmmm....

Would the same apply under the (unnecessary) cement board which is under the dira membrane?

Settlement related to home being built in 1904 plus they really chopped things up when they added plumbing over the years.
 
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