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Discussion Starter · #1 ·
SHOWER REMODEL: Any thoughts on mounting cultured marble wall surface directly onto Redgard-coated substrate?

My cultured marble fabricator / installer says he often mounts directly onto plywood or gypsum board. No Redgard, no nothing. But all I can think about is the corner joints, which will only be sealed with silicone. If water ever works its way behind that silicone bead...

So I'm thinking if I coated my substrate with Redgard then we're good, assuming PL 90 / PL 700 will bond to the Redgard.

Thanks.
 

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Most of the cultured stuff we pull out is thrown right on the drywall. Unless the adhesive would eat the red guard I would think it would be a nice extra level of protection. I would do a test spot of redguard on a piece of drywall and throw some adhesive on it and see what happens.
 

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Discussion Starter · #3 ·
Thanks. Looking into Georgia-Pacific's DenShield. Claims to be waterproof backerboard. Exterior surface is a deeply-wrinkled acrylic enamel. If I paint Redgard into the corners of this substrate, it might be a good solution.

If anyone's used this product, would appreciate any input.

Link
 

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Just make sure you prime the surface with redgard for proper adhesion. If the substrate is bone dry it will suck the water out if the redgard and cause a poor bond. Prime by mixing 1/2 redgard and water. Haha don't ask me how I know.
 

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Discussion Starter · #6 ·
Heard back from CBP. They say if you want to apply onto Redgard any adhesive other than thin set, to do the following: Apply a skim coat of Speed Finish Patching & Finishing Compound onto the RG then apply adhesive onto skim coat.
 

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I like to use flashing (butyl) on corners and seams when I install cultured marble or granite slabs on shower walls . The thinset or pl will not adhere to the butyl but it is a relatively small area over all . It's the last line of defense but a very good one .
 

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I like to use flashing (butyl) on corners and seams when I install cultured marble or granite slabs on shower walls . The thinset or pl will not adhere to the butyl but it is a relatively small area over all . It's the last line of defense but a very good one .
Everyone has their own ways, but where does the water go when it hits the flashing?? It's going to dam up somewhere unless the bottom of the panels are left unchalked.
 

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Just make sure you prime the surface with redgard for proper adhesion. If the substrate is bone dry it will suck the water out if the redgard and cause a poor bond. Prime by mixing 1/2 redgard and water. Haha don't ask me how I know.
Ok, I won't ask you how you know this because there's a damn good chance you made this up. How "dry" do you think Durock might be? Pretty dry, huh? Yea, that's what I thought. Redgard is a "water borne" product, not "water based." The water in the product will dry up and leave the water sealing qualities to cure like they are designed. I'm pretty sure I've read the directions on the container and there's no instructions for "priming."

You are supposed to apply a minimum of two coats onto whatever surface you are using as a base, whether that be sheetrock, Durock, plywood, concrete, blocks, or whatever. I use a small roller and it dries so quickly, that by the time I finish the entire shower, it's usually dry enough to second coat.

I don't do cultured marble panels but I've taken them down and I don't ever remember there being any waterproofing behind any of them, and the only time I remember any water damage was a panel that was broken.
 

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::blink::

You could look at custom building products' spec sheet for Redgard. Taken from the instruction sheet on their site under surface prep...

Bonding to lightweight concrete or gypsum based surfaces

... Prime all surfaces to receive RedGard® with properly applied manufacturer's sealer or with a primer coat of RedGard®, consisting of 1 part RedGard®, diluted with 4 parts clean, cool water. In a clean pail, mix at low speed to obtain a lump-free solution. The primer can be brushed, rolled or sprayed to achieve an even coat. Apply the primer coat to the floor at a rate of 300 ft/gallon (7.5 M/L) of reduced material. When dry, apply at least one full coat of RedGard® to the primed area.
 

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I use a primer coat of Red Guard on cbd. I think it soaks into the pores of the cbd better than a full strengh coat. The first full strengh coat now has something to grab to when rolling it on.

However, you could trowel it on, too. In that case, you're pushing the matetial into the pores so I wouldn't prime.
 
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