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amadog
10-09-2006, 10:07 AM
Hello,

I've had several bags of this relatively old thinset (> 1 year) laying around in my garage, for over a 1 year, and decided to use it to lay down the hardibacker 1/4" boards on my new bathroom floor, before laying down tile.

This old thinset, which was never opened, was in my unheated garage, sitting on top a styrofoam base, did have large clumps which I had to crush, and then mix. Other than this, the thinset had the same consistency and feel as any other thinset I've always mixed.

The other day I had a water spill accident, and a section of the already layed down hardibacker, screwed in and applied with this old thinset, got extensively wet. What I noticed was that the thinset that I could reach turned into a muddy consistency and was able to be wiped off, even though it was set and cured several days prior. Then I tested to see if it was possible to remove a piece of hardibacker board. I was able to lift it right off. My previous experience has shown me that once thinset cures, it's cement, and it doesn't turn back into a muddy mess, like this one did. Is the reason for this because the thinset is bad (past it's expiration date, which it doesn't have on the package). Or would the mixing, too wet, or too dry, affect the thinset in this way?

Now, the current issue...is that I layed the whole floor with hardibacker 1/4" and this old, supposedly expired thinset. Should I worry? I plan to level the floor with SLC anyway, since the floor is pretty off-level on one side, afterwards I plan on applying a liquid membrane like RG to complete the prep for the tiling. What I will do immediately is throw out the old bags of thinset, buy only a couple this time, and do all my seams with the new thinset.

Thanks,
Amado

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bbcamp
10-09-2006, 10:12 AM
Yes, you should worry. Thinset can hydrate in sealed bags. Your year old thinset probably has. Good plan on throwing the old stuff away and buying only what you can use in a month or so.

Shaughnn
10-09-2006, 10:15 AM
Amando,
Once it's put into the bag at the factory, it starts to absorb moisture. SHelf life rarely exceeds 6 months, though I try never to use anything older than 3 months. If the bag has been opened, reduce the shelf-life by half.
Shaughnn

amadog
10-09-2006, 10:22 AM
OK, I will worry, but I think it would be ridiculous to uplift all that hardibacker now, figuring I will be applying the SLC, and the RG. I don't see how I can get it wet afterwards. Of course, I will start using new thinset for everything at this point. What do you think guys?

Thanks,
Amado

bbcamp
10-09-2006, 10:37 AM
Your floor is only as good as the materials you used in it. Your floor, your call.

Trask
10-09-2006, 11:42 AM
We cycle through thinset pretty fast and if a I get a bag that's suspect It becomes fill...Just too much liability to take a chance with such an intregal portion of the job.

jadnashua
10-09-2006, 05:23 PM
The clumps you broke up should have been a major red flag...once cement hydrates, you can't for practical purposes drive the moisture out again...it has been incorporated into the molecule - it is no longer water, but part of the cement. WHat you had was bascially sandy cured concrete mud since most of the cement was already cured. If it was a modified thinset, the texture may have been from the latex modifiers...it will break down. Now, the thinset under cbu is to fill voids and provide 100% covereage, but sand is asking for trouble I think.

JSaffle
10-09-2006, 10:14 PM
Is there a way that I can tell whether I may be experiencing a similar issue with bad thinset? I laid some Ditra over Versabond over plywood. I noticed that the bag was dated 08/05; it had a few clumps that seemed to break up easily.

I found a few dried pieces of the thinset that were left over on a drop cloth and wet them. They did not seem to break down, but I could snap them in my fingers. I could grind them against one another, and they would break apart.

The Ditra seems to stick well. I had a couple high spots that caused me to cut out and replace some small section of the matting. It resisted being pulled up, but I could pull it up by hand with a good tug. When it came up, the fleece was mostly intact, and I could see the texture of the fleece and ridges in the thinset.

The project is a small bathroom, and I have not yet laid tile on the membrane. If the thinset does turn out to be bad, now is the time to fix it. Any thoughts or ideas?

Thanks,

Jim

Shaughnn
10-09-2006, 10:32 PM
Jim,
That's over a year old and YES, the thinset has expired.
Shaughnn

JSaffle
10-09-2006, 10:44 PM
The thinset under the Ditra that I replaced would mostly scrape up with a chisel and drywall knife difficult to scrape all the way down to the plywood. If I pull up the remaining Ditra, do I need to remove all the thinset completely down to the plywood? Or is 'gray' plywood OK?

Jim

Shaughnn
10-09-2006, 11:01 PM
Jim,
The subfloor has to be clean of flat and free of debris. I take that to mean that mounds of spent thinset aren't acceptable. You don't plan to reuse the Ditra after you pull it up, do you?
Shaughnn

JSaffle
10-10-2006, 08:15 AM
What I meant was that I can scape up most of the thinset until the floor is flat, but there will be a small amount that wants to stick to the plywood almost like a (very) thin skim coat across the floor. It will be quite an effort to get the floor down to completely bare plywood.

Although the Ditra might come up with the fleece intact, I have enough to repeat the job and will probably trash the used stuff.

This was my first thinset project, so I do not have any experience to compare what unexpired thinset should be like. How should it behave after curing? If I were to examine it, how would I know that the process worked?

Thanks for all your help.

Jim

Shaughnn
10-10-2006, 08:31 AM
Jim,
If you have access to a beltsander and a large shop-vac you can use those to take down the remaiing thinset. Because this thin-set is questionable you really don't want to bond to it, as it is going to be the weakest link in that bonding chain. If you sand the floor, use a wel-fitted respirator or at least a dust mask.
You'll know if you've got good coverage by using a gray thinset and watching to see the Ditra darken as you press it into the thinset bed. You want the whole floor to have that dark backing, as any light areas means that you don't have a bond.
Best of luck,
Shaughnn

sgrandjean
10-10-2006, 08:32 AM
Jim,
I'f it's possible, you might want to find a tile supply house that carries thinset. They seem to rotate through their stock a bit more than the big box stores, and I'd guess that you'd have access to a batch with a 'born on' date that is closer to the purchase date.
Cheers.

JSaffle
10-10-2006, 10:36 PM
All,

Thanks for your insight and advice.

Jim

jdkimes
10-10-2006, 11:56 PM
I assume that this expiration would hold true for grout as well.
Bag of grout that's been sitting around indoor for a year even here in dry Colorado.

Trask
10-11-2006, 03:50 AM
Jeff, I don't know for sure in your part of the country... but here in Astoria Or. it rains more than I care to mention and our grout definetly has a shelf life.

jdkimes
10-11-2006, 07:54 AM
It doesn't rain here and it's very arid.
I don't see any chunks or anything in the grout but still wonder if on micro level the cement has adsorbed water and cured.