Thinset (thin-set) : Changing Water Ratio's that are spec'd by manufacture

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JohnfrWhipple

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"Never mix mortar outside of the manufacturer's liquid recommendation." - I read this quote this morning on another online forum. Sadly this forum does not have the ignore feature and the poster of this comment is from our local Kerdi Salesman Jim. You can read it here:

What a contradiction to previous posts. I ask you how do you mix thin-set loose to follow the spec's by the sheet membrane makers and not over water the thin-set?

Something has to give. I think it's more reckless to follow the measurements than not. I find that the thin-set is never loose enough when mixed by the book. My experience has shown me that you need a premium sheet membrane that allows any type of thin set. Something like NobleSeal TS, NobleSeal CIS or Laticrete's Hydro Ban Sheet Membrane. And you need to jack up the water ratio.

I have privately tested Latcirete 254 thin-set mixed 20% heavy on the water content. Even with this added water the thin-set passes all my private shear testing tests.

This one point is a subject of much debate. If you call the makers of the sheet membranes they ask for the thin-set to be a little loose. Ask the maker of the thin-set and they say follow the rules. As a builder, tile guy or DIYer - you need to bend one of the rules. Which one do you bend?

I say buy the best thin-set you can. Then mix it a little loose. Not to loose. Depending on the time of year I add between 10-20% more water with my Laticrete 254 mix. I once set a brick over Ditra with this mix. I hung over 1600 ponds of water off of the brick. I tried this same test with AF207 and the brick slide off the substrate still attached to the uncoupling membrane.

Time and again I have run other tests measuring tensile and shear forces. All with the 20% over water mix. Time and again something else failed before the thin-set. When the thin-set did fail it was always at a higher rate that required.

What would happen with a cheap ass thin-set like a VersaBond or non-modifed? I don't know the answer - I never use these cheaper products....
 
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JohnfrWhipple

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CX - smarter than the tile manufactures own technical man himself.

LOL - too funny. If you read the thread on the other forum you see near the end of the discussion the Ardex technical rep recommending Ardex X5 for a Kerdi install and to get non sage thin-set. CX (I think he is the primary shareholder of the other forum) chimes in to say it's required to use non-modifed thin-set.

Why this is funny to me is that CX knows that Ardex allows this and that he is debating with the company directly. Why is this? I think this is because Ardex does not sponsor the other forum. I think this info that Ardex allows modified thin-set with Kerdi is a dirty little secret that Schluter does not want spread. I believe this since it is an unfair playing field for all the other companies.

Anyone using Kerdi would be foolish if they did not work with Ardex thin-sets.

If you call Ardex they will confirm this and they will give you a ten year warranty.
 
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ShowerDude

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again, an opt out clause for any possible wrrty claim by mfg. to cover thier ass yet still sell slogans and jargon.

the warrenty ? false advertising.
 

JohnfrWhipple

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Makes you wonder sometimes.

One of the worst thin-set I know of for #^&#ed up water ratios is Ardex X32. I was told by a top salesman it's OK to modify it somewhat. I was told in training (Ardex Class) to follow the mix. In the training the Ardex Tec had to add more water.... TFF

I laughed my ass off. The water level on X32 is out to lunch.

Once again it comes down to location and skill set. And I warn a DIY if you try and follow every rule you are going to run the chance of something not working out that well.

I add 10%-20% to the Laticrete 254 spec. And that is 10%-20% on top of their high end. That's my recommendation. I like it. It works for me. I also wipe the back of my sheet membrane and flat trowel the cement board first. So clearly I have no clue what I'm doing.... lol
 
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Jadnashua

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For Schluter, they allow any A118.1 mortar to be used. They recommend DitraSet. If you read the installation instructions for DitraSet, they allow 5-6 quarts of water to be used. So, still being within their mixing instructions, mixed with 6qt for the full bag would be 'looser' than if mixed with 5qt. To embed the fleece properly on their sheet membranes, using the full amount is the better choice, and, is fully within their instructions. Setting a large format tile with the same DitraSet, mixed with 5qts, it will be thicker and perform better on that larger, heavier tile. FWIW, DitraSet is called out as both a thinset and a medium-bed mortar on their product sheet. Some products give you a range, some do not. Not following the instructions can give you unpredictable results. Too much water, and the cement particles end up further apart than designed. They can only grow their crystalline structure so far, and that happens way before all of the water is either used up in the process, or evaporates. That means that the tips of the crystals are only interacting with the ends of adjacent particles...they end up being much more fragile. Read my thread on US thinsets in the Tutorial section.

I was at a workshop at Mapei earlier this year and they showed us some microphotographs of overwatered thinsets and slc products...the aggregate tends to settle out of overwatered mixes, and the cement floats to the top. Only when mixed with the designed amount of liquid does the material retain the full capability of the product. Choose the proper thinset for the job, mix it properly, and you should not have an issue. There are a huge number of different ones out there, and for use on any specific product, those designed specifically to work with it often tend to give easier, faster, better results. At least several companies make mortars specifically designed for use with membrane installation. If you want to make your job easier...use one of those and mix it per instructions.
 
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