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Unread 08-23-2011, 04:08 PM   #1
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Steam shower slip joints..is it really a sign of plasticizer loss?

Thinking about this slip joint thing today from another thread. And I really can see where the walls would move that much to cause a problem..one that caulking could not fix.

After thinking of a few things I am wondering if this whole problem is related to product design.

I might be wrong here but certain clues are pointing to a concern I have always had with sheet membranes. Plasticizer shrinking!

1. the problem seems to be only recently an issue...perhaps due to the membranes getting older and losing plasticizers.

2. Heat greatly speeds up plasticizer loss..this recommendation is only for steam showers..correct? Also as far as we know that the only place the problem happened...so far..

3. membrane shrinks from plasticizer loss and if two walls are attached without this slip joint then it would pull the corner of the membrane out of the corner when it shrinks..no? That would be the first logical place to go if a sheet product incountered shrinkage.

4. if this is the case and these product are susceptable to the more than 51% plasticizer loss rule(if interested in that..just ask..kinda involved).. WHAT will happen to these membranes after fifty years!

5." new installation specs" im my 28 yr. experience in many facets of different trades. Are usually ALWAYS brought upon by failures..and the first thing companies do is try to fix the problem through installation ..easier fix that way.

Maybe I am being paranoid here but all sales hype aside even with the improvements in high end vinyls these days last I checked they still have plasticizer loss. Why sheet membrane companies after I have inquired always told me their products did not shrink..Always seemed suspect to me..but I digressed since im not a chemist.

Could this be a glimpse of possible future membrane shower failures?
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Unread 08-23-2011, 05:33 PM   #2
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Jim, good post. I do believe only time will tell. Noble has been at it the longest, so i'm interested in what Eric has to say.
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Unread 08-23-2011, 06:12 PM   #3
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Well after I wrote this I did some googling on cpe membranes..And found LDPE and HDPE (low density and high density polyethylene). And found out I am a little off base..while PVC is very suseptable to plastisizer loss Like I mentioned above..CPE is not the same type animal.

However I did learn that while CPE has alot of great characteristics, the two main weaknesses of it compared to other membranes is that it has the highest amount of thermal expansion(they were talking like a meter in a 100 foot..80c temp change) Thats alot even with less heat, also it has problems with stress cracking from being bent..particularly the thinner membranes.

So again I start thinking..maybe with the heat changes in a steam shower maybe what we are really dealing with is expansion..not shrinking as I was previously thinking..

1. In believe Schluter wants kerdi'band used rather then bending the membrane(am I correct on this?) Is this to avoid stress bends?

2. The slip joint is folded into the corner rather then creased.

3. The slip joint due to the nature of it's shape could also provide a place to the material to expand..as well as shrink.(perhaps thats why normal caulked corners over normal folded bends still failed..it's pushing not pulling. And the tile hits the edge much like not leaving expansion space around the perimeter of a room. But this time it's not the wood swelling it is CPE expanding with temp changes.

4. That would explain perhaps the buckling effect DG mentioned if I understand him correctly.


And I quote"Yes, I have been on failures where the walls buckeled and there were no slip joints, several where they had caulk joints at grout joint depth but not through the backing. Have only seen it on commercial though a few loose tile residential jobs. I can see theoretically how you would do a slip joint with a liquid but I have never seen one done myself. Because it is unlikely they can or will be properly constructed my preference is and remains sheet products whether residential or commercial steam. Piano hinging a sheet is easy."


Again I am not a chemist just some food for thought on this slip joint issue that I tend to find kinda odd...beings we didn't need them for the last 2000+ years when everything was just cement that was not affected as much by temperature.

Warning: I might be totally off base on this theory, anyone that understands this stuff better please educate.
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Unread 08-23-2011, 07:09 PM   #4
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Were steam showers built before kerdi came around?

If laticrete wants poly behind for the vapor barrier, couldn't one just use poly and a conventional liner and silicone them together?
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Unread 08-23-2011, 07:24 PM   #5
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Nice thinking Jim.

Do you consider the membranes as polymeric materials ?
Also , do you consider the need of the slip joint as the need of the soft joint , when using this membranes?
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Unread 08-24-2011, 04:48 AM   #6
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My experience may have nothing at all to do with this PVC thread, but here I go anyhow. When talking about membranes, PVC to me is a four letter word. It got that way back in the 80's (?) when PVC single ply roofing was first being introduced in this area. We were told it was the answer to our prayers compared to a conventional builtup asphalt. So we used it on 2 fairly good sized buildings, one manufacturer was Trocal, the other Water Guidance Systems. There was a five year absolute watertight guarantee on both.

You guessed it, at about 6 years old, both membranes failed. They shrunk so much that they were pulling 30" high masonry parapets out of plumb by as much as 2" to 3"!! Then the membranes shattered, which meant that there were literally hundreds of cracks in the field of the membrane. Neither manufacturer would do anything because the roofs were out of warranty. The Trocal rep told me years later that what happened is that Trocal took their membrane that was working well in Europe and started manufacturing and marketting it here. Problem was, in order to save money, they significantly reduced the amount of plasticizers in the membrane.

In the years that I was in architecture, there were only 2 products that we would NEVER use in a building for anything. One those was a PVC membrane of any type.
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Unread 08-24-2011, 06:12 AM   #7
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Quote:
Originally Posted by Jim
1. In believe Schluter wants kerdi'band used rather then bending the membrane(am I correct on this?) Is this to avoid stress bends?
Schluter has no qualms whatsoever about "bending" the membrane. K-band is not a requirement. Kerdiband is actually the exact same material as Kerdi, just thinner.
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Unread 08-24-2011, 10:24 AM   #8
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One thing I'm having a hard time with is were is all this expansion and contraction coming from when using the Kerdi system? Maybe lack of venting, when using a steam shower in a bath do people use poly behind the drywall to minimize all this excess moisture from entering the walls?
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Unread 08-24-2011, 10:26 AM   #9
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Quote:
Originally Posted by Chad
...when using a steam shower in a bath do people use poly behind the drywall to minimize all this excess moisture from entering the walls?
I should hope they'd be smarter than that.
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Unread 08-24-2011, 11:00 AM   #10
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Cx I'm not talking inside the shower I'm talking about the rest of the bathroom? Look I have never done a steamer and have admit I have no clue on the proper way to do so, so be nice. My question was were is all the expansion coming from? Is it just from heat or vapor the shower should be pretty vapor proof with the kerdi system correct so it must be the heat.
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Unread 08-24-2011, 12:33 PM   #11
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Not meaning to be unkind at all, Chad, just don't want any potentially serious misunderstanding laying about for future readers, eh?

Outside the shower, steam or otherwise, the moisture control in the room should be handled with an appropriate ventilation system.

In some climates, the use of a vapor retarder on the inside of exterior walls is mandated by code and in some of those climates that's even a good idea from a building science standpoint.

But in no climate would you ever want to have a moisture barrier or vapor retarder on both sides of a gypsum board panel, not even on an interior wall.

The need for additional movement accommodation in steam units is gonna be due to both heat and moisture changes. If you're using a vapor barrier on the inside of the walls, you'll be dealing mostly with temperature variation and those swings can be pretty dramatic.

If you're using a vapor barrier behind your wall board, you'll not only have the big temperature swings, but swings in moisture content, too.

In some methods, such as that recommended by Noble Company, you have some areas of each in there. Lots of potential for differential movement in various places.

The larger the shower, the greater the potential movement, of course.

My opinion; worth price charged.
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Unread 08-24-2011, 12:51 PM   #12
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Sounds like a full mud shower with membrane would be the ticket for making a solid unit that will not be affected by all the movement or no?
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Unread 08-24-2011, 12:56 PM   #13
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No.

That's the only interior application I'm aware of where the recommendation is to cut the mud walls at the changes of plane. Look at SR613 in your Handbook.
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Unread 08-24-2011, 01:34 PM   #14
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I don't think I want to sign up to do one of these anytime soon, sounds way to problematic.
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Unread 08-24-2011, 04:21 PM   #15
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Like was said..even if we have no real scientific knowledge of plastics, If the membrane is directly under the tile..we can all but eliminate moisture hitting the wood framing members as the culprit. And just how a vertical wood stud could cause horizontal expansion of any real degree is another mystery to me

That just leaves thermal expansion of the CPE,(which is apparently a well known weakness of CPE)

Of course we also have thermal expansion of CBU,Mud,Tile/grout etc...But last I checked that number was like 1/8 in a hundred feet..almost negligable....compared to CPE at over three feet in a hundred feet.

Is this an advantage K-board has over membranes? Is that why a new system that does the exact same result was invented at great cost?


Personally I like sheet membranes and trust them more then liquids and will not discontinue using them even if their is any truth to this theory of mine. But one thing I will do is use slip joints the best I can when I can.

@ Cx, the cutting the mud spec in steam showers may be due to moisture finding it's way thru the paper to the studs..hence the rule..guessing.
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