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Unread 11-21-2019, 08:54 AM   #16
cx
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Traci, do I understand you to mean you oriented the grain on your second layer perpendicular to the grain of the first plywood layer?
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Unread 11-21-2019, 04:54 PM   #17
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Plywood has significantly more stiffness across the outer plies versus along them, so, hopefully, the second layer is oriented the same way, across the joists, as the first, but offset per the instructions. Your installation is expecting the stiffness between the joists from the ply grain crossing them, not along them.
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Unread 11-25-2019, 09:04 AM   #18
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oh no. will that compromise the job, even in a 4 x 6 space? I thought I read to do it that way.

This is my little "master" half bath so it doesn't get a lot of traffic or abuse, but if I need to redo it, please let me know.

Additional next step questions:

it passes the 3' level test. I have heat system that is only going to be in about 10 sqft - the rest is vanity or toilet. I have ditra and have read old posts stating that it should go under the ditra mat; however, that seems to counter the structural importance of the mat bonding to the thinset layer.

Does it make a difference if it is under or over?
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Unread 11-25-2019, 09:26 AM   #19
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Well, Traci, your original subfloor met the absolute minimum requirement for a ceramic tile installation, so you haven't really hurt anything by installing the second layer in the wrong orientation, but you haven't gained much, either. Up to you whether you leave it or correct the error.

You'll not get any advertised benefit from the Ditra, or similar product, unless it is installed directly below the tile installation. You'd definitely want it on top of any heating system.

My opinion; worth price charged.
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Unread 11-25-2019, 09:44 AM   #20
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I'm missing something, certainly not the first time and not likely to be the last.

Traci, if you are installing Ditra Heat mat, directly bonded to the new and clean plywood you recently installed, you don't need anything else under or over the Ditra Heat mat.
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Unread 11-25-2019, 09:48 AM   #21
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It is a different and separate heat mat. They don't locally stock the heated ditra ...although I am considering adding the time and expense to return what I have and go that direction.

I really appreciate your help.
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Unread 11-25-2019, 10:04 AM   #22
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I would, Traci, I really would.

The Ditra Heat mat is very easy to install and nearly fool proof. I mean, if I can do it...…

Might be a little more costly but will make up for it with ease, and piece of mind, installation.

Been there, done that, as have others here. Let us know how we can help.
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Unread 11-25-2019, 01:47 PM   #23
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Quote:
Originally Posted by Dan
...make up for it with ease, and piece of mind...
Mmmm, which piece, Dan?
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Unread 11-25-2019, 02:10 PM   #24
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The only few pieces I have left.
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Unread 12-10-2019, 11:50 AM   #25
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So my saga continues with another question....

I have a perfectly laid double layer of plywood to which I added thinset and heated ditra and then pre-filled the ditra cavities. It all works perfect except I think there is a little 4-6 inch area that did not completely adhere to the plywood and thinset.

Is this a deal breaker? Will I ever finish this job???

Your humble opinions are greatly appreciated!
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Unread 12-10-2019, 12:46 PM   #26
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What make you think a small area didn't adhere to the plywood, Traci?

But, in short, yeah - a deal breaker I think. The good news is it shouldn't be too horrible to fix, because thinset mortar doesn't really stick to Ditra, and since it's a small area digging the mortar out, and moving the wires out of the way, cutting out that section, cleaning the mortar off the floor, and installing a new piece, shouldn't take too long.
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Unread 12-10-2019, 01:45 PM   #27
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I don't doubt your expertise but I am looking for any way around this . If it is well adhered all around, it is not in the traffic area, not needed for waterproofing and not perceptible to the eye, couldn't the tile just sit there, adhered to the thinset on top of the ditra?
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Unread 12-10-2019, 01:47 PM   #28
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the only reason I noticed is because I was on my hands and knees at eye level inspecting, patting down all within my reach from the doorway the next morning.
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Unread 12-10-2019, 01:52 PM   #29
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Traci, it's yours and you can handle it any way that makes you comfortable. Depending upon your tile size, you may get by with what you have. Or not.

My opinion; worth price charged.
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Unread 12-10-2019, 02:34 PM   #30
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well I guess I am wondering how it will fail under those circumstances. is it adherence, deflection, cracking, movement, waterproofing? what is my concern with this problem?
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