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Old 05-01-2006, 02:49 PM   #1
meierk
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Kerdi over Denshield

Ok, I know now that Denshield was not a good choice for a shower installation, but that is what my local Home Depot recommended and that is what I had installed. Unfortunately, the installer did not care that Denshield is supposed to be installed with silicon between the joints and without vapour barrier, which I have on one outside wall.

I have contacted Georgia-Pacific (manufacturer of Denshield) with my concerns and they indicated that the lack of silicon between the joint is not a problem if I use 2" mesh tape when tiling. However, they did say the vapour barrier could be a problem if water gets between the Denshield and the barrier. I asked if this would happen because of condensation or because of water leaking. They said it would only be a problem in the case of water getting past the Denshield.

This basically tells me that I can either take the Denshield down and redo with cement board and Kerdi or find another way to ensure that water can never penetrate the Denshield. This got me thinking... I have always seen Kerdi installed over cement board, but can I install it over Denshield. Georgia-Pacific indicated that they have never tested Kerdi over their product, which brings me here. Has anyone here ever installed Kerdi over Denshield? Was it successful? Did you use non-modified thinset as recommended by Schluter for Kerdi use, or a latex modified thinset as recommended by GP for Denshield use?

Kevin
Calgary, AB

Last edited by meierk; 05-01-2006 at 03:04 PM.
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Old 05-01-2006, 03:23 PM   #2
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I would think this would be a great place to use versabond...its modified so it works with denshield, its only slightly modified so it works ok for kerdi. If you have a scrap of denshield, take a small piece of kerdi and make a test board with versabond. Let it set a couple of days then try to pull them apart...if it gives much resistance, you will probably be ok. Dont bother taping the joints, the kerdi will suffice in stopping the water.

But wait for others to respond...I am only suggesting this test should you have the material and time available to try it.
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Old 05-01-2006, 04:02 PM   #3
lou432
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I`ve put Kerdi over Denshield many times! some of the builders I work with spec there custom showers w/Denshield, which I use to install right on the Denshield ,but I never caulked the corners I taped +mudded then when dry used a liguid membrane on all joints + since I`ve become a believer in the Kerdi/Schluter way , I still use Kerdi over Denshield.Until the builders change there spec from Denshield to Sheetrock.

The two trips to SC with Schluter + the numerous question+answers ,one of mine was the same as yours ; Can you put Kerdi over Denshield? YES! With what thinset? UN-MODIFIED!!! Yea you could use Versabond but it I believe it would void Schluters warranty on the Kerdi.

Good Luck!!!
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Old 05-01-2006, 04:09 PM   #4
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I think the kerdi spec says you should use whatever is appropriate for the substrate (in this case modified) and unmodified between the kerdi and tile. I suspect most modified will take a long time to dry, so I mentioned versabond. Its good to know it can be done even with unmodified thinset...I wish I had used it now instead of regular drywall under my kerdi...a little extra protection cant hurt.
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Old 05-01-2006, 04:51 PM   #5
John Bridge
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I don't think Schluter has a spec for Kerdi over Densshield. In fact, I know they don't. I know how they think, though. They are going to see two impervious layers, the Kerdi and the face of the Densshield, and they are going to want un-modified "dry set" mortar between the two.

Me, I'd use Versa Bond, but I don't cash in on warranties.

The other problem is that for the Kerdi to be effective it will have to go all the way down and overlap the shower pan.
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Old 05-01-2006, 04:53 PM   #6
Westie
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Kevin : If you do go with Kerdi the best place to get it in Calgary that I have found is Northland Construction.
If you need more Denshield let me know I have 3 4x8 sheets sitting in the garage that I wouldn't let my contractor install. He wanted to put greenborad up, I told him no way so he brought in the Denshield. At that point I told him he didn't know what he was doing and I would do it myself with cement board.
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Old 05-01-2006, 04:55 PM   #7
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Kevin,

I forgot to say Welome aboard.

Welcome aboard.
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Old 05-01-2006, 05:05 PM   #8
lou432
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Yes your right,it does say whatever is approiate for the substrate,+ I`m not disagreing with you + I think Versabond is a great lightly modified thinset .
I`m just going by what I was told @ the Schluter camp+ my understanding of the way Modified+Un-Modified bond to the substrate ,chemical bond vs mecanical bond ,air cure vs wet cure? Plus + gota make sure that I`m doing it to 100% specs for the warrenty ,cause I want to do it right the first time plus I don`t want to eat the job later.

I definitly agree with you if you ment Denshield when you said;I wish I`d used (it) instead of sheetrock? I guess it wouldn`t hurt although I feel quite comfortable with sheet rock+ Kerdi.


FYI... I tore out a custom shower two weeks ago that some one else did 6 or 7 years ago+ used durock on half the walls+Denshield on the other half + the half with Durock was wicking 6-10 inches up the wall + the Denshield had wicked less than 3/4 of an inch. The bed had a Sheet membrane + an ajustable drain with the weep holes filled with mortar so it the bed was completely saturated+ when the walked on itto shower the preasure from there weight + more water was forcing the saturated beds water up+over the sheet membrane +into the framing+into the Dinning room ceiling+light fixtures.

A lesson not to learn!!!!
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Old 05-01-2006, 05:15 PM   #9
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Quote:
Ok, I know now that Denshield was not a good choice for a shower installation
If done right, I prefer Denshield over other products.
But nobody read instructions these days. so doesn't matter what they use it will probably have problems.
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Old 05-01-2006, 05:44 PM   #10
meierk
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Unhappy

Thanks for all the answers.

I did speak to GP today and they said to use a modified thinset with Denshield so Randal's answer makes a lot of sense. I think I should use Versa Bond to bond the Kerdi to the Denshield and unmodified thinset to bond the tiles to the Kerdi. If anyone has any strong objections based on experience, I would like very much to hear from you.

BTW John, I was thinking about doing something over the custom mortar shower pan, but wasn't sure if I should use Kerdi or Ditra. I should point out that the shower is in the basement and the floor going up to the shower is a dri-core subfloor. I was told I could spread a layer of thinset over the dricore and then installed Rhinoboard over that with screws about every 6 inches followed by my tile.

I also have an added challenge that the shower needs to be wheelchair accessable so I will only have a small curb or hump which I was thinking of making out of plywood. Problem is, I'm not sure how to do this. My shower pan is made up of a mortar bed, then a rubber membrane, then another bed of mortar that brings it up to the plywood hump. Do I need to add metal lath to the plywood and mortar over the lath and then install the Kerdi from the shower out to the main floor or am I over thinking this whole process?

Maybe I need to install Ditra over the Rhino board up to the shower and then bring the Kerdi out of the shower over the hump and overlap the Ditra and then I take two tylenol and consume a bottle of whiskey

I am a DIY'er, not a pro and I have quickly learned that the "so called" pros at Home Depot don't earn my confidence. I seem to get a different answer depending who I ask and which day of the week I ask.

Kevin
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Old 05-02-2006, 09:01 AM   #11
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Sealing Dens-shield

Kevin,
I can relate to your problem.
I am installing a prefab shower (neo angle type), my problem is that I have 6 inches to tile between where the shower ends and the celing begins, plus the celing.

I figured Dens-Shield would be the way to go since it comes in 4x8 sheets and I wasn't able to find (or maybe I just wasn't looking hard enough) full sheets of cement board.

Now my problem is how do I seal the joints? I am thinking about using Kerdi (if I can get it in small enough quantities, I only need a coner bead strip about 80 inches long).

Or....since this theoreticaly isn't going to be a high water contact area...do I need to worry about sealing the joints with Kerdi? I think I should as I don't have a lot of room between the shower head and celing. If I have another foot or so I wouldn't be so concerned.

Any thoughts?

ps....I hear ya about hd in cowtown
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Old 05-02-2006, 10:18 AM   #12
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Lou,

What I meant in that I wished I had used it instead of drywall, was for the sake of the water wall. Now I think schluter says its ok for cbu on the water wall as extra precaution...but mine is already up and I aint changing it. I did however paint the back side of the drywall in the water wall area with a couple coats of redgard and the studs too...cause I already had some left over from another project and figured what the heck.
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Old 05-02-2006, 06:25 PM   #13
Kirk Grodske
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You can buy a small roll of Kerdi Band from Tile Experts for $17.00
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Old 05-02-2006, 06:34 PM   #14
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I don't know about the plywood "hump." Can't see that it would work better than mud. The main thing is to keep your shower pan higher at the front than the surface of the shower floor. Otherwise, water will ooze through the floor mud and over the edge of your pan. Don't know how you're going to get around that. Or maybe I'm not getting the picture. That seems to be happening with more and more frequency.

If I could get my hands on Ditra Set (I can't), I'd use it for everything. It is the most wonderful dry set mortar I've ever used. If you can get it, use it.
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Old 05-03-2006, 05:14 PM   #15
meierk
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Only reason I was considering a plywood hump is because the mud bed I created doesn't seem very stable. I created a dry pack bed and after it dried I accidentally spilled a little water on it. It was like pouring water into soft dirt - it just washed away. A few days after that, I was vacumming off the bed to clean up all lose debrise before installing the pvc liner and I vacuumed several pieces right down to the concrete floor under the dry pack.

Maybe my mix was not correct, but not being a pro, I have no way of knowing. In anycase, I am very nervous about creating the bed on top of the liner.

Kevin
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