Failed Thinset??

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  #1  
Old 06-04-13, 12:52 PM
J
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Failed Thinset??

I'm trying to understand what could be the casue for a thinset failure. At least I believe I have a thinset failure. I installed a porcelin tile floor in my kitchen/laundry room about a year and a half ago. The entire floor failed. I was able to pull up ALL of the tile by hand. The only thing holding the tile in was what little grout remained and the weight of the tiles themselves. I would say that 99% of the thinset was stuck to the underlayment and not the tiles. Here is what the install consisted of:
3/4 inch subfloor
Durock cement board secured by liquid nails, roofing nails, and screws
Mapei thinset (I don't recall which one specifically)
Porcelin tiles
Mapei grout

My feeling is that the thinset failed. Could it be an issue with the tiles themselves?
 
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Old 06-04-13, 01:09 PM
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No tile expert...but obvious the thinset didn't stick to the tiles. Causes? Wrong material, thinset allowed to sit too long or too dry a mix, trying to do too large an area at one time.

Oops....liquid mail instead of thinset under the Durock? Is that recommended?

Still doesn't explain the lifting of the tiles with a clean back. How big were the tiles? Should they have been buttered before setting?
 
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Old 06-04-13, 01:21 PM
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Part of this floor was set by a "professional" tile setter. he gave the OK for the thinset. he also mixed his own for the portion he set. He back buttered, I did not. the tiles are 6x6, 12x12, and 18x18. I agree that the liquid nails is probably not the proper way to adhere the durock as well. I let them sit per the thinset instructions. They felt very well secured before the grout went in.
 
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Old 06-04-13, 01:35 PM
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Cement board in liquid nails - wrong
3/4" only subfloor - probably wrong, not thick enough
Tiles did not stick - Thinset mixed too dry, or tiles not properly set into thinset - they should be "wiggled" into place and then use spacers to hold

With 3 different size tiles, you made a more complicated pattern lay for your floor. This takes more time to think through which piece goes where. Thinset has a limited working time and may have skimmed over or the cement board drew out too much liquid before you got a chance to set the tile.

We need additional information to move forward. What size and span and spacing is your floor joist system?
 
  #5  
Old 06-05-13, 03:02 PM
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Mapei makes many different thinsets. Some are suitable for setting porcelain tile, and some are not. Porcelain requires a good quality modified thinset. Without knowing the exact product used its not possible to tell you why the tile didnt bond. My guess is that the wrong thinset, probably a cheepo thinset was used.

The liquid nails under the cement board certainly didnt help the situation any.
 
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Old 06-06-13, 10:08 PM
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I vote that you used the wrong thin set, if everything else was done right, ie; trowel notch size, open time, etc.

Beads of construction adhesive instead of 100% thin set coverage under the board is a sure way to get hairline cracks in the grout in a few years, but not related to this issue.

You need to tell us what thin set was used, cuz there's virtually no chance Mapei's mortar is defective. It's almost always installer error.

Jaz
 
 

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