Correct thinset for glass mosaic tiles on kerdi/ditra

[Karen_BC]

Hi guys,

I have been an avid reader of this forum for the last couple of weeks. Thanks to all the information provided I’ve managed so far to forge ahead with my bathroom remodel even though I am a first-timer.

But now I feel that I need a little bit more direct support since I can’t figure out which thinset I should use to attach the glass mosaic tiles (translucent with coating on the back, face mounted on paper) in my shower.

The tiles are supposed to go onto:
a) the back of the shower niches cladded in KERDI and
b) 3 feature strips in between the white ceramic field tiles (to hide that I got fooled by the nominal size of my tiles ) where I already attached some DITRA strips to make up for the height difference between the tiles.

Really appreciate your help.

Karen

[muskymike]

Hi Karen, welcome. You will need to use a non modified thinset with a latex additive added to it instead of water. TEC makes a thinset called super flex that all you have to add is water and it sticks to glass. You will have to let it dry for a few days before grouting being on the kerdi.

[Karen_BC]

Thanks for the good advice. Does anybody know where I can buy TEC products in British-Columbia? I have only found US dealers online.
Thanks
Karen

[John Bridge]

Hi Karen,

There are other brands. If you can get TEC you can use their dry set with latex additive. Call my friends at Interstyle (makers of glass tiles in Van, BC.)

http://www.interstyle.bc.ca/

[Brian Barbier]

Just to add a note on this subject...
I have been back and forth on this issue of modified thinset requirements for materials being used on a kerdi system that has an unmodified requirement.
The consensus from Schluter related folks is don't use modified on kerdi at all. Well, the last phone call to Schluter got me that answer specifically, anyhow. But of course the product manufacturers of porcelain and glass all say use modified. And a speaker at a tile conference who covered ANSI 118.4 says that's exactly what modified thinset is for. So, my most recent solution: back butter the glass mosaics with modified thinset, a very thin layer, and set them into the unmodified I used everywhere else in the shower.

Maybe the pros here can start a consensus thread, where everyone puts in their $.02 worth, short and sweet, on their take on this situation... just a thought...

Brian

[Karen_BC]

I just had an interesting talk with the tech support at Interstyle (John, thanks for the tip) and they suggest to use Mapei Grani Rapid (they had good results with their tiles on waterproof membranes - or as an alternative Kerabond Keralastic).
They also recommended that, since I am dealing with a small paper faced mosaic tile on a shower floor, to use the thinset as grout.
Which means to trowel the thinset into the grout joints of the tile sheets, then slightly backbutter the tiles, trowel a thin layer of the same thinset onto the kerdi and press the tiles in firmly (and no, they don’t see a reason for using an unmodified on top of the kerdi since Grani Rapid will set up quickly in between two impervious surfaces).
The downside of this method is that there is no way to make adjustments to the tile layout: the paper will be dampened and removed only a couple of hours later. And since the thinset will be more permeable than grout it will need a penetrating sealer (has to be repeated after 6 to 8 months and after that on a routine basis).
K.

[John Bridge]

yes, I figured they would tell you about rapid set, and if you were to check with Schluter, I think they would go along with that also.

But I think you can use regular modified thin set with 1x1 in. tiles. Air will get to them.

[Karen_BC]

Originally Posted by John Bridge

But I think you can use regular modified thin set with 1x1 in. tiles. Air will get to them.

Yeah, confuse a poor newbie right now I am ready to use my heat gun – just kidding!

But seriously: Glass tiles/Grani Rapid/Kerdi might be a compatible trio but mix in my non-existing skill level and I fear that my shower floor will be doomed – if anything I need time to get stuff right.
So before you suggested the „regular modified“ I was about to order some Superflex - but unless I am driving down to the U.S. I have to wait for at least 6 weeks.
So my question: would you use „regular modified“ for the shower floor and the the 1 inch strip in between the wall field tiles? And by „regular modified thinset“ do you mean Versabond (or is this not modified enough) or are your referring to some other product?

Thanks again for the input!
Karen

[jadnashua]

From what I've gathered from reading here, IF you can afford to wait awhile before you grout, then modified is okay. The non-cement components of the modified thinset need to dry, and with a waterproof membrane underneath, and big tile with few joints like a dense porcelain, there is almost no surface area to allow those components to dry out. They will, but since the grout lines are the only means of escape, it can take a long time, maybe a week or more. But, in your case, you are using small mosaics - lots of grout lines per square area, thus lots of breathing rooom for the moisture to evaporate. I'm not a pro, nor have it tried this, but I've put porcelain tile on top of Kerdi with Versabond, let it sit, and it certainly set up hard as a rock. So, take that with a grain of salt...if you can wait for it to dry, go for it...the glass is difficult to get to stick if you don't.

[John Bridge]

That's the way I see it, Jim. Give it a few days before you grout it. I don't know that I go along with using white thin set as grout. That's been a mess every time I've tried it.

Sorry for the confusion, Karen. We are opinionated.

[e3]

i may be wrong , but I thought the glass tile people DID NOT want to be bonded directly to a membrane.They want the membrane behind the Backerboard..(oceanside scott flemming ?)

[NCTILEMAN]

Eric, you may be right, but that sure would rule out using kerdi for glass tiles. The little amount she has would probably be okay though.
Gary

[tileguynky]

Originally Posted by John Bridge

I don't know that I go along with using white thin set as grout. That's been a mess every time I've tried it.

Sorry for the confusion, Karen. We are opinionated.

Now if somebody would just make a white grout that matches the white thinset. No matter how hard I try, always seem to find the little spots of thinset that protrudes through the grout. Have tried to let the grout dry to see if it would match once cured, so far no luck. Tried with TEC and Custom Megaflex. Not much fun cleaning grout joints out on 1x1.

[John Bridge]

Eric, We don't even know whose glass tiles these are. They are only 1x1s, and she can use any modified thin set to stick them on initially-- the grout will hold them in after it sets. She isn't going to be walking in the backs of the niches.

Again, Karen, let the tiles dry a couple days before grouting -- just to make sure that all of the thin set behind them has dried. You are sandwiching modified thin set between two impervious surfaces. It needs to air dry, and it can only do that from the edges of the tiles.

Now I would not want anyone to construe this advice as applicable to a floor or to larger glass tiles.

[Karen_BC]

Thanks guys,

So far the glass is sticking just fine and I am happily tiling away.

As far as the shower floor is concerned (yes, the same glass tile mosaic is supposed to go on there as well – but it might be a while, I still have to tackle the kerdi drain/mud bed) I am leaning towards using Mapei Keralastic/Kerabond (readily available around here) unless you have a better suggestion.
BTW I can’t believe how much excellent advice I have been getting on this board – you guys are the best

K.