# redguard on densGuard trap moisture?



## wopachop (Feb 12, 2008)

thought i read on john bridge that if you use a liquid membrane like redguard over hardibacker you must not use poly or felt behind the backerboard....saying that could trap moisture. 

so if densGuard has a build in moisture barrier would that mean i can use redguard?

i called the tech line and the dude said you dont need the redguard but its ok to use it. wouldnt the seam leak without redguard? and anyone think redguard could trap moisture when used on densGuard. not sure where the moisture would get in maybe from behind where the two panels meet. 

also im trying to decide what order to do this shower what would you guys recommend?

should i install densGuard and tile wall before even doing the top layer of deck mud on the shower pan? seen a couple pics on the other forum of people doing it that way. its only a 3x3 shower. thanks for any advice


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## Bud Cline (Feb 12, 2006)

When a waterproof board such as Denshield is used you use no moisture barrier behind the board. You must however address all the seams and fastener penetrations. (I'm not personally familiar with "densGuard" but it sounds like the same type product.

If by saying "top layer of deck mud" you are saying you intend to do a two-cast floor then the board shouldn't be installed first.

If you are doing a KERDI or CIS application then you can install the board first.


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## wopachop (Feb 12, 2008)

Bud Cline said:


> When a waterproof board such as Denshield is used you use no moisture barrier behind the board. You must however address all the seams and fastener penetrations. (I'm not personally familiar with "densGuard" but it sounds like the same type product.
> 
> densGuard is sold at lowes and is blue instead of gray but the same as densShield. when you say address all seams is that just thinset or do you use a liquid membrane on top of the thinset..?
> 
> ...


i asked the same question on a motorcycle forum but there are couple tile guys...one dude said i should tile the wall before finishing the shower pan with the top layer of deck mud. what do you guys think?


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## WarnerConstInc. (Jan 30, 2008)

Did you ask the Sons of Anarchy, I think that is a tv show.


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## WarnerConstInc. (Jan 30, 2008)

I really dont think Densguard and Denshield are the same thing.


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## JazMan (Feb 16, 2007)

DensGuard is not the same as DenShield. You do not want to bury these boards in the deck mud. Look at their instructions & sketch. They are kinda vague in their instructions I think they want to avoid the obvious? However, when installed after the deck mud, how do you fasten the bottom 6-8"? You shouldn't puncture the membrane behind. Another reason I only do Kerdi showers. 

Jaz


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## MattCoops (Apr 7, 2006)

I once asked a tile guy how to rake out the forks of my harley
He said it wouldn't ride level


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## wopachop (Feb 12, 2008)

no densGuard and densShield are exactly the same product except for the color. there used to be a thread i even took close up pics of both boards but my search wont find it. i guess lowes wanted blue...densGuard come in 3x5 sheets and densShield is larger i forget now.

the guys giving advice on the motorcycle forum are tile contractors they seem to know alot.

so you guys understanding the question im sorry i suck when it comes to trying to explain stuff..? 

maybe im just trippin....is it true that when installing hardi backer with a moisture barrier behind the board you would not want to also use a liquid membrame on the front of the board because it could trap moisture?

thats why im wondering if using a liquid membrane with densGuard is bad since it has a built in moisture barrier.


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## Bud Cline (Feb 12, 2006)

Looking at their respective websites both products appear to be basically the same product. 

GP has this to say: "_Since DensGuard has a built-in moisture barrier, never install vapor retarders directly behind DensGuard Tile Backer."_



> address all the seams and fastener penetrations


Seal them with something.

I see absolutely no reason you couldn't coat Densguard with RedGard if that's what you want to do. You can certainly "address the seams and fastener penetrations" in that fashion. Coating the surface directly WOULD NOT be the same as installing a moisture barrier then installing DensGuard over it.

My furnace doesn't seem to be working properly! I think I'll go to the NASCAR Forums and see if I can get it fixed.


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## wopachop (Feb 12, 2008)

Looking at their respective websites both products appear to be basically the same product. 
yeah im positve man...there was a thread i think you were even posting in it...bout 3-4 months ago but i can find it by searching.

GP has this to say: "_Since DensGuard has a built-in moisture barrier, never install vapor retarders directly behind DensGuard Tile Backer."_



Seal them with something.

I see absolutely no reason you couldn't coat Densguard with RedGard if that's what you want to do. You can certainly "address the seams and fastener penetrations" in that fashion. *Coating the surface directly WOULD NOT be the same as installing a moisture barrier then installing DensGuard over it.*
right....but what im trying to figure out is what happens when you redgard the seams on the front side of densGuard...since the densGuard has a built in moisture barrier on the back.

ill try to explain it again sorry. i read that its bad to use redguard on hardibacker seams if you used a moisture barrier behind the hardi. maybe i can find the thread and post the link.

My furnace doesn't seem to be working properly! I think I'll go to the NASCAR Forums and see if I can get it fixed.
ah you guys are gonna rip on me now :laughing: its actually a forum dedicated to glamis dunes....its a huge area of sand dunes in socal where we ride dirt bikes and dune buggies. but there are like 30,000 memebers....lots of construction guys.


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## Bud Cline (Feb 12, 2006)

OK OK OK, let's back up!

Both Denshield and DensGuard have a protective surface on the face of the board. THAT is the first line of defense and THAT is the surface that must be respected. When it comes to seams and fastener penetrations they can (and will) render the surface "not waterproof" anymore, unless those breaches are repaired. Caulk, silicone, RedGard can be used for the repairs and covering the seams after they have been filled with thinset.

Now, the second line of defense with those products is the interior of the board. It is made of components that are not effected by moisture. I have tested Denshield and found that to be 100% true of that product. Even if moisture should get through the surface-cover the moisture won't hurt or deteriorate the board's interior. BUT, you still don't want moisture getting through so you repair the breaches and seams.

NOW, the surface is already waterproof so you wouldn't want a moisture barrier behind the boards also to create a "moisture sandwich" trapping moisture between the two water barriers. If the surface is however truly waterproof then condensation can still be an issue in there.

HOWEVER, to apply additional waterproofing (RedGard) to the already waterproof surface of the board will not have any effect on the interior of the board and will not create the feared "moisture sandwich". (Bytheway - I think that is a stupid sounding term, I hate it. Had nothing to do with the creation of the term "moisture sandwich.")

Do I have us all totally confused now?


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## wopachop (Feb 12, 2008)

ok i got ya....i thought the yellow fiberglass backside was the moisture barrier. 

i remember reading something about the surface of a board needing to breathe somewhat so that the thinset could set properly. wonder if the front of densGuard breaths or if its a moisture barrier.

btw densGuard is 32" not 36" wide ill go buy densShied from this other place its wider but not as tall if i remember correctly. 

ive been shimming all day those walls were pretty bad. they want a shampoo niche on that exterior wall atleast its over 1/2" bigger now :thumbup:

hey at the bottom there will be a gap in some places between the densGuard and the hot mop what should i use back there i have thinset, mortar for the curb, and deck mud but that stuff is only for flat areas i believe....what do you guys think?


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## wopachop (Feb 12, 2008)

you were right i got this from the densShield site


Q: 
To which side of DensShield tile backer should I apply tiles?

A:
The DensShield panel should be positioned next to framing with the coated (grey) side facing away from the studs. Apply mortar or mastic and tile to the coated (grey) side of DensShield. *The acrylic coating stops moisture penetration on the surface.*


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## Bud Cline (Feb 12, 2006)

> Q:
> To which side of DensShield tile backer should I apply tiles?
> 
> A:
> The DensShield panel should be positioned next to framing with the coated (grey) side facing away from the studs. Apply mortar or mastic and tile to the coated (grey) side of DensShield. The acrylic coating stops moisture penetration on the surface.


That question probably came from a techie during one of their inspirational meetings.

So.....what's that picture all about.


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## wopachop (Feb 12, 2008)

i had to shim out the backer board pretty far. in some spots the board is not touching the hot mop area.

what should i put behind the board to keep it stiff?

damn im about to do it right now just gonna use thin set i guess.


edit: i wasnt signed in and thought i had posted pics of the shower pan....yeah that pic above just shows how much i had to furr out the walls.


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