Will a bead of caulk adhere to Redgard seam?


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Old 09-21-18, 02:07 PM
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Will a bead of caulk adhere to Redgard seam?

Is it ok to caulk the cbu -tub small gap in shower wall after the Redgard is applied? If so, would you use kerdi fix or silicone and is there an application window when it must be applied?

Also, does sanding down thinset bumps and uneven spots cause any issues with Redgard adhering or will it stick to it just as well?
 
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Old 09-21-18, 04:02 PM
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Dont use Redguard, its a krappy liquid sealer and is prone to leaks when installed incorrectly,

If you want an absolute water proof membrane system look into Ditra or Prova, you will never be disappointed!!!
 
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Old 09-22-18, 03:24 AM
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Not sure I understand what you are trying to caulk ?? The cement board should come over the tub lip. Seems get filled [and taped] with thinset. You wouldn't caulk until after the tile is installed. Scraping down bumps in the thinset shouldn't be a problem.
 
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Old 09-22-18, 04:25 PM
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Kerdifix is good stuff, use it not silicone. Be sure you tool it flat if you use it. I can't speak as to the cure time of Redgard... so I would be sure you follow the Redgard label directions about double coating and cure times, then wait as long as possible before caulking. If you have to use a rub stone to smooth out your thinset seams that is fine, you might just give it a once over with a damp rag to remove any dust that might cause adhesion issues. Best to apply the thinset smooth in the first place so that all you need to do is run a wide putty knife over it to pop off any grit or bumps.
 
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Old 09-22-18, 07:23 PM
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I have a dedicated putty knife just for shower and cement board installs. First off, all seams should be taped and embedded in thinset, this includes the corners. Scape down any high spots with your putty knife. Then you apply the redgard (multiple coats).

As far as the small seam between the CBU and the tub deck, leave it as is. Your tile will bridge that gap and you caulk after you finish with tile and grout and seal. Then you caulk it to the tub.

Question, does your tub have a tile flange on it?
 
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Old 09-24-18, 06:31 AM
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Originally Posted by Marq1
Dont use Redguard, its a krappy liquid sealer and is prone to leaks when installed incorrectly,

If you want an absolute water proof membrane system look into Ditra or Prova, you will never be disappointed!!!
Marq1- Any waterproofing system will be prone to leaks if not applied correctly. There's nothing wrong with Redgard, if you apply if according to instructions it works well.

As to other waterproofing membranes for showers and tub enclosures, Ditra is typically not used. Schulter's waterproofing membrane for that application is Kerdi.
 
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Old 09-24-18, 06:37 AM
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HeresJohnny, how strong should the redgard bond be? I did a couple test spots. One primered, one just dampened board. Both resulted in initial very strong grip. Was very difficult to lift an edge but if I kept picking at it, I could easily peel away big sheets of it, that did have a thin layer of the surface cbu material embedded in it.

Does that seem like an adequate bond?
 
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Old 09-25-18, 03:02 PM
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It has a round hump all the way around. About half inch to 3/4 inch. The boards were placed on top of it, touching. I thought there should be a tiny gap for expansion joint but the shower guy insisted my cast iron tub will not move. I applied kerdi fix down there to prevent any wicking.

Redgard question. I noticed the seam that joins my hardie board tiled area to the greenboard, has some joint compound in it on the greenboard side of the tape. Technically, it's not in the shower area but pretty close, about an inch or two away.

I know RG won't stick to joint compound so i primered the whole seam (thinset shower side and joint compound side) with zinsser water based primer.

Should it be ok?
 
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Old 09-25-18, 03:58 PM
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Yes this kerdi fix is amazing!
 
 

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