Thinset/Mortar for Marble

[Yooper Jim]

Hello all. Long time reader / first time poster. Thanks for all the great info. I'm a carpenter by trade but end up doing quite a bit of tile work. Mostly dealing with stone. I have been using the schluter systems for 13 or so years and have had excellent success with them (almost always following the directions). Here is my question.

I am hired to do a marble floor installation. There will be 3 different colors of marble in a pattern. The pattern is four 12" by 12" White Thassos marble in a square surrounded by 3"x12" Hulien Green marble as a border with a 3"x3" square to finish off the pattern. So which thinset should I use.

A. I know the Hullien green MAY be serpentine so I should use an epoxy mortar.

But the white thassos is slightly transparent and could be stained with the epoxy mortar. So for the white I should use a good thinset (white in color) like I normally do.

Is there a single product that would work well for both stones or do I need to use two different products (that would be a pain!).

All tiles will be installed over ditra. Please assume everything up to that is proper.

Thanks eh!
Jim

[ceramictec]

if you have been using Ditra for that long use your regular thinset you use.

I would coat the backs of the green marble with an epoxy as a water barrier.
then set the whole floor with a white thinset per Schluter Ditra instructions.
preferably Laticrete 317.

[Yooper Jim]

Thanks Brian for the quick reply. I have read about coating the backs and think that may be the best solution. But a couple of more questions.

1. What type of epoxy do you coat the back of the green marble with?

2. If the back of the marble is coated with epoxy will it take an extended amount of time for the thinset to cure? I know that it usually cures through the stone and with the ditra underneath the only escape for water is the grout lines?

3. When you use Laticrete 371 do you mix with water or latex admixture.

4. I will be sealing the stone before grouting. Can I use a normal cementitious grout or do I need to use an epoxy grout.

Thanks again,
Jim

[Houston Remodeler]

1- I don't know what types are available around you. Know of the locally availabe manufacturers?

2- The epoxy cures fully, then the tile is installed, so its a mute point

3- Do you mean 3701? then no

4- Seal the marble first. Fusion and Spectralock will discolor the Thassos. I'd rely on cementitious grout for this one.

[ceramictec]

Originally Posted by Yooper Jim

3. When you use Laticrete 371 do you mix with water or latex admixture.

Originally Posted by Houston Remodeler

3- Do you mean 3701? then no

no , he means Laticrete 317 the un modified thinset that he knows
cures with Hydration and is what Schluter requires with Ditra.

[Yooper Jim]

Thanks Paul!

I am amazed at the wealth of knowledge and information on this web site. I always try to get things right the first time and you everyone here has been a great help. Still I'm not quite clear on a couple of things ( Due to not being specific enough in my questions).

1. "Coating the back of tile with epoxy" - When I first read the recommendation from Brian I was thinking in terms of mortar's and I pictured putting a thin coat of epoxy mortar on the backs of all the green tiles. Now after thinking about it and reading it again I'm thinking that he meant a two part epoxy resin (which is what he said, I just interpreted it incorrectly I think). I use West Systems epoxy on my boat and a hand full of other projects. Sooo.

1a. Do I just paint on an epoxy on the back of the green marble tiles?

1b. Do I need to epoxy the sides of the tiles? As I thought about installation I assumed some of the thin set would "squish" up in the grout lines (1/16") and expose the tile to water for an extended period of time, potentially cupping the stone.

3. Paul I meant Laticrete 317 (sorry for the typo). I tried to figure out what the benefit of the latex admixture is but could not find out any good info.

Thanks

[ceramictec]

its good to paint all sides of the green marble as overkill since you are using a cement grout which is mixed with water. it might be extreme but also might be worth it.

[Yooper Jim]

Thanks Brian, I figured that is what you would say. One more question. With the backs of the green marble epoxied will my unmodified thinset adhere to it porperly? I thought about possibly adding some kind of aggregate to the epoxy to give the thinset something to grab onto?