What is "Modified" thinset?

[Pirate]

You experts are always talking about modified thinset. What is it exactly?

Is Versabond and Flexbond considered modified? Does modified thinset, actually say "modified" on the bag?

I know Versabond and Flexbond is supposed to be used on floors that aren't totally rigid, right? Can you use these thinsets on any thinset application, or are there situations were you have to use "unmodified" thinset?

[Trask]

How bout I give credit where Credit is due? Dr. Henry M. Rothberg.. Founder of Laticrete is pretty much the reason we have Latex and Polymer Modified Portland Cement Mortars.
Here's a great bit on the early development from those responsible for it.

http://www.laticrete.com/portals/0/tds/tds107.pdf


The short easy answer is that adding latex and/or polymers to a thinset mortar improves bond, gives it the ability to flex, and improves work time dramatically.

Modified thinset will often be called by a number of names..."Multi-purpose", "fortified" or anything that has the word "flex" in the name.

[ceramictec]

Originally Posted by Pirate

Is Versabond and Flexbond considered modified? Does modified thinset, actually say "modified" on the bag?

Yes

[Lazarus]

Yep....I can only add that, you can take a basic, unmodified thinset and add the recommended liquid latex additive, which is more $ but results in a VERY modified thinset.

[Pirate]

So, can you use modified thinset for all thinset applications, or do you sometimes have to use unmodified thinset?

[ceramictec]

each type of thinset has a specific use and some tiles and or manufacturers require different types of thinset to be used with material.

[Davestone]

There are times i will use a non modified,like underwater,or where i don't need a modified but want more body,like a basic ceramic install over cbu,or over bare cement,but other than an underwater install(and there are underwater modifieds) you will benefit from modifieds.

[MudMaker]

Howdy Randy.. Do you have a Pacific application you wish to address?

[Pirate]

No Pacific (or do you mean Specific?) application, I just wondered, since you guys talk about "modified" so much. For my basic floor (plywood with Hardibacker, but no flexing) and backsplash, I used Flexbond, just to be safe. It seems crazy for a DIY'er to have to keep several types of thinset on hand, if one will do it all.

[Trask]

Your application is perfect for Flexbond..and for 90% of the "standard" jobs Modified thinset is the standard. Unmodified has gotten a good deal more attention in the last few years primarily because Schluter Ditra and Kerdi Membranes require it for the installation of the tile on top of their membranes.

I also have used liquid add~mix to modify unmodified thinsets..it's how we did it when I was growing up and it is still hard to beat the latex count of liquid add mix vs. dry blend modified. On a few big jobs in years past it was also a cost effective means of getting quality modified thinset in large quanities. We called the add mix "Moose Milk"...I still miss the smell of that stuff.

[MudMaker]

Originally Posted by Randy

No Pacific (or do you mean Specific?)

No I meant to say Pacific.. San Diego drew me to use the term.. seemed appropo... I use versabond for what you are doing.. It's a little less modified but still will do the job.. FlexBond is a higher cost alternative but again, still great.. It's hard to imagine the tenacity of a thinset.. It is a true marvel.