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-   -   DITRA Doesn't stick to Substrate (https://www.johnbridge.com/vbulletin/showthread.php?t=63340)

Rajanpad 06-02-2008 06:41 AM

DITRA Doesn't stick to Substrate
Hi Folks,

First of all, let me thank you for all the great advice I got from this forum. Thanks to you, I tiled my kitchen floor without much difficulties.

I have a problem with my living room, though. I tried to lay DITRA using modified thin-set (Versabond) on Plywood substrate but IT DIDN'T STICK!! What could I be doing wrong? The consistancy of the thin-set is pasty. Should I have made the thin-set more liquidy? I remember reading that it's better to have a runny mixture of thinset so that it can seep up through the membrane of ditra and bond.

One of my friend (over the phone) told me that the substrate might 'pine' or some other type of wood, rather than plywood. Would that make a difference?

My understanding is DITRA requires Modified thin-set for wood floors.

I'd appreciate any input.


John Bridge 06-02-2008 06:51 AM

Hi Raj, :)

I think "runny" might be the wrong word, but the thin set definitely can't be stiff or pasty. You need enough water to allow some to go into the wood without completely drying out the mix. The mix should be very loose but still retain the ridges when troweled on.

Also, don't spread more than you can cover quickly. If you allow the surface of the thin set to begin to dry ("skin over") before you get the Ditra down you've got a problem.

Rajanpad 06-02-2008 09:46 AM

Hi John,

Thanks for the info. I will go at it one more time tonight and with any luck I'll get it right this time.

Do you think the weather might have played a part? It was hot yesterday here in NY (high 70ยบ and the windows and the doors were open. Maybe the windflow dried out the thin-set quickly?

I'll keep you posted about my progress tonight.


ceramictec 06-02-2008 09:48 AM

did you press it in with a wood float, piece of 2x4 or something to press it onto the thinset ?

Rajanpad 06-02-2008 10:36 AM

Yep, I pressed it with a rubber float but no luck. I did the same thing in the kitchen and it worked but not in the living room. A real mystery for me. However, as John suggested, I'm going to make a different consistancy and see if that helps.

GregO 06-02-2008 11:20 AM

Hi Raj,

I agree that a looser mix should do the trick. Also make sure your plywood is as dustfree as possible - any dust or debris acts as a bond breaker, not allowing your mortar to adhere properly.

Good Luck! Greg

mozilla 06-02-2008 01:21 PM

3 Attachment(s)
I use a 2 X 4 to seat the fleece backing on the thinset & like John said, make sure you don't let the thinset slake & break the jobs into sections making sure you have enough time to get to it. The consistency of thinset should be like loose peanut butter & should hold a point.

FYI- 1st. image- i used a 1/4 v notch trowel 2nd.) checked for coverage 3rd pic) break out the 2 x4

Saldibs 06-02-2008 03:42 PM

If you spread to large an area with thinset, and you had the doors and windows open with a good air flow on a very warm day, your problem may have been that the thinset was allowed to "Skin Over" so when you put the ditra on top of the thinset the adhesion was impaired by the skin on the thinset.

jgleason 06-02-2008 04:01 PM

Good pics Randy! The pic Randy posted that shows the Ditra pulled back is a good one. If you don't get that kind of coverage then you haven't done it right!

Randy - the 1/4" trowel puts a little too much thinset down, other than that looks like good consistency on the thinset.

Rajanpad 06-03-2008 08:43 AM

Great Pictures
Hi Randy,

Great Pictures. Thank you.

Folks, I think I've discovered what the problem was. The mixture was too 'thick'/dry. I re-did it yesterday with a looser consistancy and it seemed to stick well. The consistancy I found working was the kind that won't run out of the bucket when you pour, but rather 'ooze' out. When I did spread them, it looked like the consistancy on Randy's picture.

However, I'm using a 3/8" V notch trowel, as recommended by DITRA. I did the kitchen this way last week. In your opinion, is this ok? I don't want the ditra to 'unstick' in the future because the layer was too thin.

Thank you all for your great advice.

Much appreciated.


Davestone 06-03-2008 11:34 AM

That trowel is fine.

John Bridge 06-03-2008 12:43 PM

3/8 in. V-notch is way too big for putting down Ditra. I use a 1/4 X 1/4 square notch, and I lay it at a low angle to the floor. You want enough thin set to cover the fleece, but you don't want it building up under the mat.

mozilla 06-03-2008 01:30 PM

No problem Rajanpad & thanks for the compliment jgleason. I learned all my "diy" techniques from the fine folks in this site...ditra,substrate, thinset, trowels & laying 1000' sq ft of ditra in the last 2 months is also a good teacher :)

BTW- Like John said, laying your trowel in a low angle helps ALOT.Dunno if your into ebay but i buy my 3M rolls for a good price compared to the local tile dealers here.

tiletalker 06-06-2008 07:23 AM

Having installed millions of square feet of Ditra since 2001, all the advice above is accurate. Skinning over of the thinset is the main culprit here. Remember one thing though, yes you want a soupy mix, and you need to roll the Ditra onto the fresh thinset fairly quickly and press into it with a wood block or 2x4, but do not expect the thinset to ooze up into the empty channels of the Ditra. Those channels are to remian empty to allow for subfloor movemtent once the tile is set. You guys are great!

Rajanpad 06-09-2008 09:31 AM

Thank you all for all your help, Folks.

I want to give an update. The laying of DITRA and tiles went well, thanks to all the advice I got from this forum. Miraculously, I managed to avoid most rooky mistakes (such as mixing more than I can spread before the thinset dries) though I did make some. All in all, the job turned out well.

Thanks again, Folks. I still have projects to do and I have a feeling I'll be hanging here for a long time to come.


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