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I would like to know if it is ever an acceptable practice to mix or blend two diverse thinsets together, and under what circumstances one may resort to this practice (outside of desperation to finish a job in a shorter timeframe)?

Specifically, I'm interested in Laticrete 125 with Mapei Ultralite Mortar Pro, in any ratio, as this is what was done.

I commissioned my 1100 sq ft floor (on a post-tensioned concrete slab on the second floor of a condo) to be tiled with 18"x18" porcelain tiles using Laticrete 125. So far, all of the floor has been installed with 125, except it seems that in my ~70 sq ft master bathroom, the installer has diluted the Laticrete 125 with Mapei Ultralite Mortar Pro, in a ratio that appears to be 1/3 Laticrete to 2/3 Mapei, although I would say it was likely mixed a lot less scientifically than that. I believe this was done to save time, since he was unfamiliar with 125 and did not know how much coverage he would get up front, had not ordered enough 125 at the start of the job, and so he resorted to doing this without consulting his boss or me about it.

Also, it appears the trowel used in the bathroom has 1/4" notches, while the rest of the apartment was installed using a 1/2" notched trowel. My understanding is that 1/2" is recommended for use with these larger format tiles.

As an engineer, I realize that it is impossible to know for sure what any blend of products would do without proper testing, but I'm hoping there may either be someone who has experienced this before, or may know why it is either acceptable or never a good idea to do something like this, as I am not an expert, or even experienced in this area.

Thanks!

izvinite
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2 Answers2

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I'm hoping you haven't paid yet.

I don't think any manufacturer would consider this acceptable. (You could call their tech support just for laughs and see what they say.) At the end of the day, manufacturer's specifications are what matter.

So let's assume you have a sub-standard job. Off the top of my head, here's a few options:

1- tear it out and do over. (At the installer's expense.)

2- if they won't do over, on the premise that you didn't get what you paid for, pay them less. (Possibly a number approaching zero, given the risk of massive failure. If it went to court, I can't imagine that the installer would prevail.)

3- engage a different professional to fix everything and backcharge the first installer.

4- trust the installer when he insists that the job will be fine and functional. This approach requires that you actually believe you'll be able to find him in 6 months when the tiles fail.

Aloysius Defenestrate
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It is Probably be fine. As it has been five years and no reply of bad news. Both thinsets are medium bed mortars(no sag)for tiles larger than 15". Only difference is the latacrete 125 is specially made so it can be used with or without a crack/fracture guard underlayment of some sort. As long as he used an appropriate underlayment where the mapei was used. I don't think it would be an issue.

Technically, as for me.. I always use an underlayment as a crack prevention, with any type of thinset. And If I were to use the laticrete 125. I would still use with an underlayment. But on a surface that would have more of a tendancy to flex and move. Such as, on a plywood floor on second story track home or older mobile home floor.As it would just add another layer of safety to crack prevention. Although,I have also used Mapei. Im not a big fan of the stuff, but it works. It tends to have a short pot life with too much sand and not enough cement for my liking. If you need to pick the tile up and add or remove some to help level it. It doesn't like to stick back down again, and have to scrape it off and re-apply new thinset.

Smotty
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  • Are you the `izvinite` who posted the original question answering under a new account? If not, don't presume that a failure to reply means all is good, many people come here ask a question and _never_ come back, not even to respond to explicit requests for more details. Additionally, if you'll take the [tour], you'll note that this is a Q&A board, not a discussion forum. After what seems like a wild guess at an answer, this wanders off into I don't know where about basketball and bowling. I'm not sure that's applicable as I stopped reading. – FreeMan Mar 18 '22 at 11:29
  • Please [edit] your answer to specifically _answer_ the question asked, or this will likely be deleted as a low quality post. You could even add your "one more thing", presuming it addresses the question asked. – FreeMan Mar 18 '22 at 11:30
  • That's the standard engineering axiom: Quality, Price, Speed: pick two. (Applies to just about everything, really.) But what does that have to do with answering this question? – FreeMan Mar 18 '22 at 12:24
  • Then please [edit] your question to A) highlight the actual answer, and B) remove all the chatty commentary, as that's inappropriate for this board. As it stands, it's hard to determine exactly what the answer is, and I'm not the only one who thinks so, as I'm not the one who clicked the down vote button. – FreeMan Mar 18 '22 at 12:33
  • I answered his question. If it is OK mixing those two types of thinset mortars for the type of application they were being used for. The latter part of my response was to accredit my experience and to add deeper insight into a product that applies to using the type of mortar substrate he was inquiring about. The second is referring to a layman's installation technique. By using bowling and basketball profession for people to relate the leveling system technique. aids similar to someone who relies on bumpers or trampoline to do thier job. Last, help any readers interested. Not get ripped off – Smotty Mar 18 '22 at 12:57
  • I agree with you on that one, just my two cents. – Smotty Mar 18 '22 at 13:04
  • But my reply definitely answers his question better that the previous response.if someone came here to look if they can mix the two mortars. But the replies were 4 "what if" options with no knowledge about the materials used . IT doesn't even answer any questions – Smotty Mar 18 '22 at 13:05
  • Happy? I deleted the extras. Guess nobody wants extra advice.that pertained to his question. It's not like people had to read it all to get the answer. It was added after people who were more interested in the subject more than others. – Smotty Mar 18 '22 at 13:19
  • Plus I think it was me who down voted my own comment as I have too fat of fingers for a cell phone – Smotty Mar 18 '22 at 13:21
  • Eventhough I answered his question. Then went on how apply it and a certain technique that is now most commonly used and. As to what type of finished product, (not flat floors) of the same type of tile install and material used. The individual who asked the question. If two types of mortars the installer was mixing what. Which would also accredit exactly what you can expect to get from 90% of installers similar, either subbed out of hourly. If read throughly my entire respone was related entirely his question application and situation,what to look for not pay Quality prices for subpar work – Smotty Mar 18 '22 at 13:54
  • In response answering questions with insight to a question. As people have different interests.One not interested would skim read say, its needless chatter not relevant. But to others interested, as an informed indepth answer to relate to or understand. Even to the simplest question.EXAMPLE Question:What kind of butterfly is yellow black and big, I have never seen it before? Answer:A monarch butterfly(someone not interested in butterflys sees answer any more is irrelevant).. yet, continues to why they have not seen one.Describing generation migration and homes destroyed built on habitat. – Smotty Mar 18 '22 at 14:45
  • I have never seen one before?is not a direct question , but can be implied and have an answer into why.. similar to the question a about mixing two mortars ,and as to why they may have an installer who may or may not know entirely what he is doing by observing jf he actually used an underlayment on the different type of mortar now used that requires it. What type of technique he uses and how he's employed to answer his other questions. To determine if he should replace that section without it, with insight how much to paying for a quality tile install. As prices vary from $3 to $10 perft. – Smotty Mar 18 '22 at 15:01
  • I down vote freeman comment to my answer. Cya – Smotty Mar 18 '22 at 15:04