Fiberock Underlayment

 
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Old 09-03-2008, 08:48 PM   #1
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Fiberock Underlayment


We recently did a job using fiberock underlayment, now a few months later some of the 18x18 tiles are not bonding. We have never had this
problem with any other tile board. Has anyone had this happen? We
installed the fiberock using Mapei Ultraflex II, mudded it and nailed the
board down,next layed the tile first flat troweling the fiberock then
combing out the mud with a 3/8" square knoched trowel and setting the
tile. I did not backtrowel the tile. I removed a few pieces and tile has
90% coverage on the back and a clean separation from the fiberock, even
the imprint from the board is visible on the back of the tile. Never seen
this before...........
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Fiberock underlayment-tile1.jpg   Fiberock underlayment-tile3.jpg  
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Old 09-03-2008, 10:59 PM   #2
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Re: Fiberock Underlayment


From the looks of it you also didn't moisturize the Fiberock with a wet sponge to remove factory dust and encourage bonding penetration before the dry board could deplete the moisture in the thinset as should be done with all dry and dusty tile backers.

Gee bad luck huh?

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Old 09-04-2008, 12:04 AM   #3
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Re: Fiberock Underlayment


I would have thought sweeping the floor[underlayment]before and wet mud flat troweled then combed
out would have done it.
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Old 09-04-2008, 07:35 AM   #4
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Re: Fiberock Underlayment


Nope!

Those dry-ass backerboards will suck the life out of thinset immediately. They need to have some moisture soaked into them to slow down that giant sucking action. When the moisture is prematurely removed from thinset (all masonry products) the bond (if any) is weakened. The dry boards will immediately remove that moisture.

In addition those boards have an abundance of microscopic dust on their surfaces in fact they are made of dust to begin with. That dust can thwart the thinset contact even when the thinset has been "keyed" into the board, it really doesn't get "into" the board. I personally think sweeping only worsens the issue.
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Old 09-04-2008, 09:31 AM   #5
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Re: Fiberock Underlayment


My wife both greases and flours her baking pans...
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Old 09-04-2008, 12:17 PM   #6
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Re: Fiberock Underlayment


Thanks for your reply, I see now the problem, I go back to my installation sheet on this fiberock and
all it says is sweep and key in the mud.. no mention of wiping clean with water. Live and learn[the
hard way.....M
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Old 09-04-2008, 01:30 PM   #7
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Re: Fiberock Underlayment


I would never use Fiberock, it's a cheap version of Hardie which I'm not too crazy about either. You saved $2-3 per sheets by choosing Fiberock, do you feel better now?

In light of their instructions, why don't you contact USG to see what they have to say about their junk product.

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Old 09-04-2008, 06:28 PM   #8
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Re: Fiberock Underlayment


I called them ,will meet next week, we will see.
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Old 09-05-2008, 03:01 PM   #9
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Re: Fiberock Underlayment


Quote:
Originally Posted by Bud Cline View Post
From the looks of it you also didn't moisturize the Fiberock with a wet sponge to remove factory dust and encourage bonding penetration before the dry board could deplete the moisture in the thinset as should be done with all dry and dusty tile backers.

Gee bad luck huh?
Yup, this one

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