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Unread 08-21-2006, 11:16 PM   #16
T_Hulse
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Maybe their tech line will tell you different, but 3 things:
The instructions say you have to use thinset.
Their Redgard video shows them going over Wonderboard with the joints already filled with thinset.
When Custom looked at that tile that cracked through Redgard, I've been told that was their reason for disclaiming it, no thinset in joints.

Nathan I noticed you've mentioned 'never had a problem' twice. You know for every bad method you can think of their will be guys that come here & tell us they've been doing it that way for 30 years with no problems (like Jersey mud). "Not" having a problem really means nothing. For one, our sample size is too small as individuals. For two, you really don't know if you've had a problem. Tile setters are rarely called back after a year, and many of these problems take some full seasonal cycles to really show up (1-5 years).

Matt I'm not talking about an extrodinary event, more like a monthly event in well used showers. It doesn't take the same amount of force as it would to break a tile in your hands. You have the size & weight of the 2 large CBU boards where they meet with no blocking. The boards want to move independently but the tile is locked into both. It want's to crack there already. It doesn't take much of a bang to encourage it when they're not tied together well.

Shaughnn the 1/2" gap is 4x the recomended width. I don't think the boards can be adequately be locked in together at that thickness. Is it screwed or nailed?
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Unread 08-21-2006, 11:28 PM   #17
Kx250
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1/2" gaps seem big, time to get the 6" mesh tape out.
If the gaps were smaller I would red guard the rest of the wet area's on the tub (if there's no vapor barrier behind the CBU) and set it.
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Unread 08-21-2006, 11:31 PM   #18
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Tom,
Nailed with 1 1/2" galvanized roofing nails only around the perimeter. I know the stuff id landfill. I just want something I can hand the homeowners that convinces them of that also.
By the way, I also promised them I would try to track down an independant inspector in the area to document the work that's already been done and paid for so that they can attempt to recover their lost money from this licensed and bonded contractor. Jerry and Mike told me they knew of an inspector, when I was at the bar-b-que but I've forgotten who they directed me to. Do you also have some suggestions?
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Unread 08-22-2006, 06:05 AM   #19
MHI
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I thought it was just the corner joints.

Joints on the same plain should be always be thinsetted, and 1/2 inch is way too big.

How many joints did this guy have in a tub splash? I would just have one horizontal with factory edges, and the two corners.
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Unread 08-22-2006, 07:15 AM   #20
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Matt,
It was a 63" x 36" tub and the surround went to the top of a double-hung window, so there were 7 joints including the corners.
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Unread 08-22-2006, 08:51 AM   #21
T_Hulse
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If you want something in print you could use a copy of the Durock install instructions. Show them the 1/8" requirement & explain that is the optimal gap width for best locking the boards together to avoid tile cracking on that joint. Tell 'em you don't think 4x the spec'd width is good enough to do the job.
Truthfully though, I bet that maybe half the CBU jobs going in now have similar installs.
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Unread 08-22-2006, 10:05 PM   #22
stullis
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You have enough other problems on the job that require it to be torn out.
But if it was just the spacing issue I think you could deal with that. You can with sheetrock and I don't think CBU is all that much different.
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Unread 08-22-2006, 10:16 PM   #23
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It's not the gap that I'm asking about. I know it's bad. What I'm curious to learn is whether or not thinset and web tape applied over a Redgarded joint will have the same strength as thinset and web tape over virgin CBU? That's all folks.
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Unread 08-22-2006, 10:24 PM   #24
stullis
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I think that answer is NO.

Tom pretty much cleared that up. If there was any way Custom could say that I'm sure they would.
Of course Hugh (Indiana Floors) said that it could be done over pre-stressed concrete joints in that motel.
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Unread 08-22-2006, 10:33 PM   #25
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Not sure how you're gonna get a definitive answer to that one, Shaughnn. The only testing I know of that would be at all applicable would be the shear-bond testing with thinsets on CBU and waterproofing membranes. Both of those require only a minimum of 50psi bond strength to pass the testing, though, so I don't know that you'd be able to get the actual test results.

Maybe Custom would give you a straight answer if axed directly. Maybe.

Instinctively I gotta say no matter what kind of bonding results they have, the presence of a flexible membrane between the CBU and the joint mortar is gonna make the joint less rigid than bonding directly to the CBU. But I don't know how to prove it.
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Unread 08-22-2006, 10:43 PM   #26
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Scott --

Quite a memory you've got. I'd love to hear how the RedGard Motel turns out in the long run.
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Unread 08-22-2006, 10:43 PM   #27
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Shaughnn

I think another way to phrase what CX is saying is to explain to your customers that RedGard and other liquid waterproofers are not designed to have a tenacious (sp?) bond to the substrate the way thinsets are. By their very design, they want to pull away from a substrate that is flexing too much so they can retain the watertight envelope.
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Unread 08-22-2006, 10:44 PM   #28
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Scott

I had forgotten about that whole debacle. Thanks for bringing it up.


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Unread 08-22-2006, 10:47 PM   #29
Shaughnn
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Thanks all,
I think that CX and Rob finally hit on points which clicked in my head. "Contact Custom and badger them for an answer" and "designed to seperate".
Yipee! My work here is done!,
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Unread 06-30-2020, 05:50 AM   #30
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I know this post is over a decade old but I happen to be reading it and wanted to share a solution for anyone running into this issue. I believe in an easy solution to this:

-Remove the mesh tape
-Use a wire brush on an angle grinder to remove as much redgard on the joints (It does not have to be 100% removal!)
-Apply the thin set to joints

Hope this helps someone else.
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