Pre-mixed Thinset? Anybody used it?

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Old 11-29-11, 11:08 AM
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Pre-mixed Thinset? Anybody used it?

I just saw some pre-mixed thinset called "SimpleSet" or something like that. It was a little bit more expensive, but I'm tiling such a small area, I think it may be worth not having to mix up my own batch of thinset. Has anybody tried these premixed products and do they work ok?
 
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Old 11-29-11, 11:32 AM
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Every Pro will tell you to avoid them...but I would have to say it probably depends on what you are doing.

Give us some details and the advice will be better. Is it a wet area, small back splash, heavy traffic, etc, etc?
 
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Old 11-29-11, 11:58 AM
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What size tile, what kind of tile (ceramic or natural stone), where are you putting the tile?
 
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Old 11-29-11, 02:25 PM
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I personally would not use it under floor tiles, but a counter backslash, yes... as it is basically wall mastic.
 
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Old 11-29-11, 03:05 PM
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Sorry, it's for a half bath. The size of the tile has not quite been finalized yet, but well be either 12 or 18 inch ceramic tile.

I am seeing that most reviews on the internet are saying not to use the pre mixed stuff.
 
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Old 11-29-11, 09:01 PM
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I'm not an expert and have only done tile floors twice. Both times I used premixed thinset and I think it came out just fine. I have not had any issues with tiles coming up.

Both of these were very small jobs (half baths).

Again, I'm not an expert and have hardly any experience.
 
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Old 11-30-11, 07:12 AM
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Originally Posted by bigdog43 View Post
Sorry, it's for a half bath. The size of the tile has not quite been finalized yet, but well be either 12 or 18 inch ceramic tile.

I am seeing that most reviews on the internet are saying not to use the pre mixed stuff.
I believe that most of the reviews that you read on the internet are posted by tile pros that have never used mastic on a tile floor. Once it hits the internet it reaches urban legend proportion. Many are relying installation guidance provided by the TCA.

I would not use mastic on 18" tiles. The stuff takes a long time to set up under larger tiles. I have done a half dozen floors using mastic to set 12" tiles. I have never had a failure. Get the subfloor/underlayment/structure right and you won't have a problem.

One thing to know about mastic cure and cure times. It does not set up like concrete. Think stale bubble gum. Under 12" tile it takes about 2-3 weeks to cure. That doesn't mean that you have to wait that long to walk on it. Lots of pros take that cure state as a sign that it is inferior for tile adhesion. It is not.

I have (admittedly unscientifically) tested mastic adhesion, both tension and shear, cure, and water solubility. IMO the only real drawback is water solubility. Mastic will turn into snot under water. It WILL NOT fail under the sort of water exposure you might expect on a bathroom floor. Most of that water evaporates anyway - I did that test too.
 

Last edited by Wayne Mitchell; 11-30-11 at 07:31 AM.
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Old 11-30-11, 01:36 PM
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My 2 cents.

Premixed thinset isnt thinset at all. Thinset is a portland cement based product and cannot be stored already mixed in a bucket. "Premixed thinset" is mastic with sand in it. Mastic is good for backsplashes and small format tile 8" or smaller. Mastic can actually stain some natural stones. The best thing about mastic is those nice buckets that you can use over and over again.

I'd not use it on a floor. With large format tile, there is little to no ability to level the tile with mastic. The tile simply sink into the mastic creating lippage issues. As Wayne said, the mastic can take an enternity to cure, specially when using large format porcelain tile. I've seen porcelain tile removed 3 months after installation where mastic did not cure in the center area of the tile. The larger the tile, the larger the notch trowel you need to use. Using a 1/2" or larger trowel with mastic will be a disaster. Your 18" tiles will simply sink into the mastic when you use a large notch trowel. Some mastics will reimulsify when they are exposed to excess amounts of water. An clogged overflowing sink or toilet could do that. If you use real powdered thinset that you mix with water or an additive, this will not be an issue. If you use 18" tile, consider using a medium bed mortar.

As Wayne's projects prove, using mastic on a floor may not be a guaranteed failure. Setting materials are only part of a good and proper installation. A proper joist system and proper subfloor and underlayment are a must.
 
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Old 11-30-11, 03:52 PM
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HereJohnny - One of the first posts I made on this site was regarding mastic and tile. I had tiled a shower surround, not a pan, using mastic and 8" tiles. Several of the tile pros here told me to tear it down and start over. One guy called me a hack. That last one really pissed me off. So I did some research and testing. Recognizing the stupidity of tearing down a new tile job, even if it was eventually destined to fail, I left it in place waiting for it to fail. That was 7 years ago it's still just as I put it up.

The last 10 years before I retired I worked for and wrote test methods and practices for a DOD engineering facility. I also field tested them. Obviously, I no longer have access to a lab and test materials but I have tested mastic enough to convince me that it is fine when used within the manufacturers guidelines.

I tested water solubility by using two test boards with ceramic tile set on 3/4" plywood with mastic. One I sprayed daily with a garden hose. The other I submerged daily for half an hour. Board 1 showed no evidence of any change in the tile or mastic. The tile essentially fell off board 2.

To test adhesion I used four 12" porcelain tiles set on 3/4" plywood with mastic. I allowed it to cure for 1 week and then I attempted to pry the tile from a corner with a handy bar. The corner of the tile broke off. I then tried to pry a tile from the plywood by driving a 1 1/4" wood chisel between the tile and the backerboard. That lifted the tile but not easily.

To test shear adhesion I place a pull block against the side of the tile and loaded it using a spring scale. The scale maxed at 50# with no measurable tile movement.

At the end of 1 week I bored a hole through the plywood under the center of the tile to check the cure of the mastic. It was still wet, (I still could not budge the tile) nearly the same as when it was spread. I repeated the test for a period of 4 weeks using an exposed section of combed mastic as a control. It took 3-4 weeks before the mastic under the tile reached the same cure as the exposed mastic. I do know for a fact that mastic will eventually cure hard as a rock after some undetermined (by me anyway) period.

I'm in the middle of testing the water permeability of both ceramic and porcelain tiles. My guess is that most standing water (spray/drip) on a tiles surface will evaporate before it permeates the tile.

Try as I may, I cannot anywhere find any real evidence of tile failure when mastic is used as directed by the manufacturer. With that said, if I were a tile guy I would not use mastic because of the cure time. However, as a homeowner/DIYer I think it's an excellent option.
 
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Old 12-01-11, 11:04 AM
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My guess is that most standing water (spray/drip) on a tiles surface will evaporate before it permeates the tile.
I'll agree with that statement. The issue here is that the water will penetrate the grout joints, and the perimeter of the room. If there is enough water it can do some damage. Grout sealer will slow down pentration of the water into the grout but will not stop it. All it takes is one good plumbing leak.

Try as I may, I cannot anywhere find any real evidence of tile failure when mastic is used as directed by the manufacturer. With that said, if I were a tile guy I would not use mastic because of the cure time. However, as a homeowner/DIYer I think it's an excellent option. .
There is certainly a lot more to a successful tile installation than choosing a setting material. The more things you do right, the better your chances are for a successful tile installation. You have done enough tile work (and research) to feel comfortable with your installtion methods and have had success in doing so. I have seen failures on floors where mastic was used. It is not always easy to tell what caused a failure. Sometimes its one thing, sometimes its a combination of things. Short and simple in my book, the more things you do right the less chance for failure. The most common problem I see on floors set with mastic is lippage. If you start with a floor that is not dead flat, youll have issues. There is little to no leveling ability with mastic and the more you put down, the longer it takes to cure. Of course you can compensate for that by doing prep work to make sure you have a dead flat surface first.

Ive used mastic on backsplashes with small format ceramic tiles over the years with good results. You have the luxury of answering to yourself for your successes and failures. I have to answer to the homeowner for mine. The more I can do to guarantee a successful tile installation the more comfortable I feel when I leave the job. The last thing I want is for a poster here to come back and tell me I gave them bad or wrong advice. And yes, as you point out, a pro could never wait for mastic to cure to finish a job and make money.

Manufacturers of setting materials put there products thru vigorous testing and in general when they say there product will do something, it probably will. That doesnt mean its the best product for the job.
 
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Old 12-01-11, 07:34 PM
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Johnny,

Did you by chance copy and paste your answer in # 8 above? I swear I wrote those very words. Either that, or as they say, great minds think alike.

As already stated several times, pre-mixed "thin set" is NOT thin set at all. For an adhesive to be thin set it has to be made with Portland Cement. All you've got there is mastic which is inferior and costs 3-4 times more. It does have its uses though. Kitchen backsplash or any vertical dry area using certain types of tiles.

I would never use it on floors or wet installation. It is easier in some ways, but not to be used if you're looking for high quality results.

Jaz
 
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Old 12-02-11, 10:46 AM
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but not to be used if you're looking for high quality results.

I don't understand. Assuming all other factors being equal and following the manufacturer's instructions, what would keep tile set with mastic from being a high quality job in say a dining room floor or a kitchen floor? In those applications what property of mastic makes it "low quality"?
 
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