unmodified and modified thinset mortar

I am going to be using versabond thinset mortar purchased from home depot.

It says fortified thinset. But no where can I find whether it is modified or unmodified.

Can I use this for both under ditra and above?

Below ditra is gypcrete

Yes, it's modified, if Schluter will quarantee this application, then go for it, I would talk to them first.

Ditra is great stuff. But expensive. Made for germany because it is illegal to mecanically bond to a substrate over there. Also made for tile pros to cut down on labor hours. It sounds like you shuld contact schluter before venturing into this product.

Ditra is a great product, the gypcrete is the problem here.

Schulter said use unmodified instead of modified

What is gypcret? Is it like masonite?

Tony-- when setting the tile, use unmodified. However, underneath you want a modified (fortified) thinset.

I am getting very different answers. I called schulter and they said use unmodified thinset for both layers. Then the guy that sold me ditra said use unmodified between gypcrete and ditra. Use modified between tiles and ditra.

I just bought unmodified thinset premium plus from hd made by custombuilding. I guess I will be using this between the gypcrete and ditra. It says u can mix with water or with acrylic mortar mix instead of water for a stronger bond. Do I need this mix? IF I added this mix, does it make my thinset modified then?

I am starting early tomorrow morning

Yes, it makes it modified. If Schluter says to use the unmodified in both places, then do it.

So I used unmodified thinset for under ditra using custombuildingproducts premium plus.

But according to custom buuilding products, the do not recommend ditra as a sublayer at all.

Here is the link

http://www.custombuildingproducts.com/docs/tech_bulletins/TB9%20Bonding%20to%20DITRApdf.pdf?user=diy&lang=en

And also while schulter recommends unmodifed for both below and above ditra, custom building products is recommending using modified thinset and actually the ones with strong bonds and additives.

This is really confusing. Should I go ahead and use unmodified and follow what schulter says? Or since I am using custom building products's thinset, should I follow their recommendations and use a modifid thinset with strong bond?

Help

Tony, use modified thinset for everything ok. This really shouldn't be that confusing. I do it all the time and the only thing it affects is the set up time, meaning you may want to wait another day before you grout especially if it's a porcelein tile your installing. Never ever had a problem.

The reason is (pros) is that my store never orders in un-modified. I bring in every copy of the
Tile Letter ans every other magazine I get but I think all they do is look at the pictures

Ya might pull them aside and whisper to em that it's CHEAPER. They'll hear that!

I have and it goes in one ear and out the other.

I've actually spent hours upon hours on the showroom floor educating the consumer.

Salesmen are not installers and about all of them learned by listening to me.

Use unmodified thinset. It's not a question of adhesion, the vinyl component of modified thinset needs air to dry unlike unmodified thinset which reacts with the water you add, to set. So if you sandwich the thinset between two waterproof and basically airproof layers like, for example, ceramic tile and ditra, the only way for the vinyl to set is for it to slowly react with the air that gets exchanged between the grout lines before you grout.

I'm not saying that the modified thinset won't eventually set, but it would take a long time and the ultimate strength of the installation is sketchy at best. The reason that people have "sucessfully" used modified thinset in this type of application is that because it is still mortar, the yield strength of the thinset still gets fairly high even without the vinyl component being fully cured.

If you still insist on using modified thinset be aware that because of the small surface area that is actually exchanging air (the grout lines) you will need probably on the order of one and a half to two months for the vinyl in modified to achieve cure (and you can't grout until then, otherwise the vinyl will be blocked from the air) If you use modified thinset between two impermeable layers like Denshield and ditra it will probably never properly set.

Why would anyone use DITRA over Denshield to begin with?

OH, BY-THE-WAY - This thread is more than four years old and has been laying dormant all that time until now, but thanks for the input.

Mike T is giving you the correct advise. Its all about drying time. Go to Home Depot and read the instructions on the ditra package.

Who should go to HD to read instructions?

BTW, HD does NOT sell an unmodified thin set that I would recommend for setting any tile. All Custom makes now is Custom Blend, a very cheap mortar.

I recommend following Schluter's instructions, so in this case unmodified should have been used.

Jaz

I've used customblend for the last few years and have found it to be an real good 9/10 mortar. No problems thus far. Got it in me own home too

Well, it does meet minimum standards and I'm sure it'll work just fine for wall tiles and soft bodied floor tiles on concrete. I & many pros just don't trust anything that cheap for floors that get much traffic. Why take chances to save $3-4 per bag as compared to a good quality unmod?

I'd rather use better quality materials than just bare minimum.

Plus I believe this thread had mentioned Ditra and again they and I recommend a premium unmodified to set all tiles on it.

Jaz

I get what you are saying Jaz but I had to rip that mud up before and it bonded like an SOB. It stuck to the tiles and pulled out of the Ditra waffles. I always thought that if unmod mud was anymore premium it would have the polymers in it. I know this is reply 20 but lets keep it going this is interesting and educational I saw bags of Multiset there and never gave them a shot either. Only to keep my prices down did I go with the $5.89 bag. Thanks for your help on this one