ditra for heated floor

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Old 02-14-13, 08:53 AM
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ditra for heated floor

Hi everyone

I'm doing a heated porcelain floor installation in my kitchen (100 year house) and I'm trying to figure out if I need ditra. My wife doesn't like the idea because it will raise the floor, but we're looking into what kind of transition ramp we could install. Besides that, there's just the extra cost that makes me wonder whether we could do without it. I do want to make sure it's done properly though so we don't have issues in the future.

What's the prevailing wisdom for heated tiles, to ditra or not to ditra? 12" x 12"

FYI, the flooring contractor has told me he'd use cement board over our plank subfloor, as opposed to plywood. The joists are 2 x 8's, 16" on center, with an 8' unsupported span.

Thanks for your help!
 
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Old 02-14-13, 09:34 AM
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Cement board is not structural, it cannot be used in place of plywood.

You structure is fine for ceramic but the planks probably are not, best to remove them and put 3/4" plywood in their place with CBU or Ditra over top of that.
 
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Old 02-14-13, 10:06 AM
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Since reading your comment I've looked around online and I see some debate about whether plywood or cement board is better, but I don't see anybody saying "you cannot use cement board under tile." Sorry for being questioning, I just need to make sure I know what I'm talking about before telling my contractor I don't like his methods.

So can you explain further why I can't use cement board? What am I supporting structurally? In my mind it's just the heating wire, ditra, compound, and tile, and lots of people seem to do that with cement board.
 

Last edited by jpenns; 02-14-13 at 10:25 AM.
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Old 02-14-13, 10:26 AM
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I'm not saying you can't use cement board, I'm saying plywood and cement board have different purposes and can't be interchanged for each other (cement board is what I mean when I say CBU later in my post).

Plywood is for structure, cbu is for creating a proper bonding surface for the tile. You need both of them is what I'm saying, or you can substitute Ditra for the cbu.

That make sense?
 
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Old 02-14-13, 11:27 AM
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Ahh, ok I think that makes sense. When he talked about using cement board it would've been without Ditra. So I definitely need plywood. Check.

Now onto the other part of what you said, removing the planks. Can you clarify why that is? If the plywood went on top of the planks would that not work?
 
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Old 02-14-13, 11:58 AM
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Tell us more about them - size, orientation, ....

Generally speaking, tile over planks is a bad idea.
 
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Old 02-14-13, 07:23 PM
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I'm concerned about this;

Originally Posted by jpennes
FYI, the flooring contractor has told me he'd use cement board over our plank subfloor, as opposed to plywood.
That tell us he doesn't have the knowledge or experience to be doing the job.

I looked at the pic in your other thread concerning this project, and although there's no description and the pic is too tight, I see hardwood over something. Looks like two layers, yes?

On the wire and Ditra; You'll want to SLC over the cables probably, so make it 1/2" and then tile over that. Otherwise you might (?) be able to go thinner and then install Ditra.

You say adding Ditra would raise the floor too much? Why? It only adds 1/8".

Jaz
 
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Old 02-18-13, 10:07 AM
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The planks vary in width but are about 6" on average. They're 1" thick, and they run diagonally to the joists.

EDIT: after investigating a bit, the separation that makes it look like two layers is just the groove where the hardwood fits together. It's all just one layer of thick hardwood.

I too have my questions about this flooring guy but he's brought in by my general contractor, who I trust. They're willing to do what I specify re: plywood but it's unnerving having to be the guy who knows what's necessary, based on the advice of strangers online. Thanks very much for the help.

I've decided the ditra will work. I think the flooring guy didn't want to use it and made it seem like it would add significant height. Now I just need to figure out if I can go over the planks, and what thickness of plywood I need
 

Last edited by jpenns; 02-18-13 at 10:23 AM.
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Old 02-18-13, 07:41 PM
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It's not a good situation for the layman customer to teach a contractor how to do an installation.

.....................based on the advice of strangers online.
The point exactly, so, who's looking out for your benefit and who's taking your money?

Now I just need to figure out if I can go over the planks, and what thickness of plywood I need
Not sure what you mean here. No, of course you can't put Ditra on the planks. The thickness of the new underlayment depends on the condition of the planks. If they're perfectly flat 5/8" should do. If the planks had been t&g and perfectly flat, I would have said 1/2", but they're not.

Jaz
 
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Old 02-22-13, 11:20 AM
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It's not a good situation for the layman customer to teach a contractor how to do an installation.
No, I didn't mean putting Ditra directly on the planks, just wanting to make sure that I don't have to take those planks out before putting plywood down. Cause that will complicate things significantly. I'll use 5/8" plywood. Thanks
 
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