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Unread 07-28-2006, 11:27 PM   #1
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Smile Can Redguard adversely affect KERDI?

My husband and I recently ripped out our old shower and have begun to put in a new one. We opted to use a KERDI shower system, which was relatively easy to put in. The contractors around town who've used this product also go over it (once set) with a layer of Redguard as an extra waterproofing measure. My assumption, after reading about the product, is that one does not need to use Redguard if a KERDI membrane is in place and that the contractors are just taking this extra step out of superstition/habit. But because they recommended we also use Redguard, I purchased some. Now I am having my doubts, however.

My questions:

1. Can the Redguard actually interfere with the performance of the KERDI membrane or adversely affect it in any way? Is Redguard harder to adhere to than the KERDI membrane for the mortar/tile? I'm leaning toward not coating the KERDI with Redguard unless someone with more expertise (almost any of you on this forum, for sure!!) than I convinces me otherwise.

2. Also, before I tile the bathroom floor, would it hurt to put down a coat of primer or Redguard to seal the subfloor? I've never tiled anything, so I am learning as I go, but so far, so good--the KERDI was easy enough for even me to work with!

Thanks for any advice you can offer.

Kathy : )
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Unread 07-29-2006, 12:57 AM   #2
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Unless you want to set up your own testing laboratory, it's going to be difficult to get an authoritative answer to your question. I can guarantee you that neither Schluter (maker of Kerdi) nor Custom (maker of RedGard) has tested the two products together. And neither of them will honor their warranties since you are following the installation instructions for neither.

Kerdi is a great product. You get a shower that is just about 100% watertight all the way up to the shower head. A shower that will dry out quickly because the waterproof layer is just behind the tile. A shower that does not have a drain with pesky weepholes that will clog. A shower that is really first class.

RedGard is a good product and has its uses. But a Kerdi shower is not one of them. You don't need RedGard. You don't want RedGard. Take the RedGard back to Homer.

If you start to have doubts, just close your eyes and repeat to yourself, "I do believe in Kerdi. I do believe in Kerdi. I do believe in Kerdi." until you believe in Kerdi. Your faith will not be misplaced.

Go Rutgers!
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Unread 07-29-2006, 01:12 AM   #3
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1) No, it won't interfere with the performance or adversely effect it. RedGuard is not harder to adhere to. There is no reason to use both products although it can be easier to use the RedGuard in corners and niches without the build up you can get with kerdi.

2) Would it hurt? No, but if you want to waterproof the floor , why not use some ditra and kerdi on the seams?
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Unread 07-29-2006, 05:46 AM   #4
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don't do it

Do not apply Redguard to your Kerdi you would once again be creating a monster. It is amazing to read posts on this website concerning Kerdi and the many methods of installation most of which do not conform to Schluters recommendations . If you have your Kerdi installed then you are ready to start setting your tile and return Reguard to the store you brought it from for a full refund.

"It was a woman that drove me too drink, and I haven't found her to thank her yet" W.C Fields.

Last edited by phobbs; 07-29-2006 at 08:31 AM.
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Unread 07-29-2006, 06:36 AM   #5
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Hello Kathy,
I agree with the others who've said, "Don't do it". Kerdi, when installed properly, is waterproof on it's own. Your local "sages" are engaging in some homebrewed mayhem and you should not follow their direction. Use that extra money you get from taking the Redgard back to the store and buy a nice shelf or accent tile for your project.
Best of luck,
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Unread 07-29-2006, 08:25 AM   #6
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Smile Thanks, all!

You all are confirming what I was assumming--RedGuard at the very least is overkill. I DO HAVE FAITH IN KERDI...I DO HAVE FAITH IN KERDI...I DO HAVE FAITH IN KERDI.

There, I'm completely over what the guys here have been telling me!

Funny how old habits die hard--I'm sure that's why these guys are giving me that advice...and they all love KERDI.

Now on to actually tiling, which should be interesting, since I've never done that, but I'm patient. I'll check out what you recommended for the subfloor.

Thanks again!

Kathy : )
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