Difference between latex modified thin-set and polymer modified thin-set?

QUESTION

Modified Thin-set Cementitious Adhesives - Can you tell me the difference between latex modified thin-set and polymer modified thin-set?

ANSWER

ANSWER - There are modified thin-set adhesives that meet ANSI A118.4 or ANSI A118.15.  They can either me latex modified thin-set where you add the appropriate liquid latex rather than water or there are polymer modified thin-sets that have dry polymers in the powder and when you add water it activates them to give similar performance as the latex modified thin-set.

7 thoughts on “Difference between latex modified thin-set and polymer modified thin-set?

  1. Donato Pompo says:

    It isn’t that simple. First you need to know what kind of brick it is and whether it has any type of coating on it that you can see or not see. An easy test is to put water on it and see if it readily absorbs. If it does then generally it can be bonded to with a thin-set mortar. If it has a coating or doesn’t readily absorb water then you have to scarify the brick with some type of grinder.

    Once the brick is suitable for bonding to it, you should use a modified thin-set mortar that at least meets ANSI A118.4 requirements to skim boat the brick substrate. If the brick joints are deeper more than 1/4″ then you have to use a mortar that allows for a thicker application such as a Large and Heavy Thin-set mortar that can be applied as thick as 1/2″.

    Depending on the application you might have to float a mortar bed over the brick by first screwing in metal lath.

    After the brick substrate is properly prepared then depending on what type of tile you are installing you need to select the correct thin-set mortar. If it is a porcelain tile an ANSI A118.4 thin-set will normally work, but for glass tile and some other more difficult to adhere tiles you have to use a ANSI A118.15 improved thin-set mortar that will achieve better bond strength.

  2. Troy Carrington says:

    Unmodified or polymer modified thin set for large format (12′ x 24″) marble tile in shower wall application?

    • Donato Pompo says:

      Most thin-set manufacturers recommend either an ANSI A118.4 or A118.15 polymer modified thin-set mortar for porcelain tiles. Schluter is the exception. They use to only recommend ANSI A118.1 non-modified thin-set mortars when installing over their membrane, but now they produce a polymer modified thin-set so they might have changed their mind..

  3. Troy Carrington says:

    Thanks for the quick reply. They do make 3 new types (one of which is their All-Set, which is a modified). So given that, what I currently have meets A118.4 A118.11, which is the same as Schluter’s All-Set, the only difference is the brand (Custom)? Also, long story, but would that same polymer modified thin-set work over RedGuard?

    • Donato Pompo says:

      In theory, any polymer modified thin-set that meets ANSI A118.4 would bond to Custom Redgard membrane. Although it is always best to go with a single course manufacturer for installation products. So if you use Custom Redgard you should use their thin-set and grout. If you use different manufacturers for the different installation products and you have a problem then they all point fingers at each other. If you use all from the same manufacturer then you only have to deal with one company if there is a problem.

      • Troy Carrington says:

        Thanks again. I figured it would be that way, but as I said, long story. Had a contractor use both and do a really horrible job (he’s no longer on the job). So I’m left with what is here and going to finish it myself. Picture a patchwork quilt. Thanks for all your insight!

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