# Shower- backer board and mud base



## HS345 (Jan 20, 2008)

Nope, rubber roofing is composed of rubber (go figure), pan liners are not. 

Sealer in no way, shape, or form, stops water. Read the label. Sealers allow vapor transmission by necessity.

You might try researching industry standards for tile assemblies. 
I'm not engaging in a pissing contest either, I just wouldn't want anyone to read your postings, and think this is a proper way to build a tiled shower. No offense.


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## JKRasku (Jan 7, 2007)

angus242 said:


> Kerdi (or other sheet membranes) keeps the moisture IN the shower. .


I probably havent done enough research, do you use normal thinset and grout? What do you use to seal the seams?


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## angus242 (Oct 20, 2007)

JKRasku said:


> I probably havent done enough research, do you use normal thinset and grout? What do you use to seal the seams?



Not sure which seams you're asking about.

You (or others) may ridicule my procedure but I stand by it. There may be other ways to do it, but I doubt there are better.

Starting in the stud bay:
Blown-in cellulose
No vapor barrier
DensArmor
Fiber tape seams
Kerdi w/Kerabond
Kerdi-BAND seams
Tile w/Kerabond
Urethane grout

Unless there's natural stone going in the shower (and I discourage that), no need to seal anything.


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## BuildersII (Dec 20, 2009)

HS345 said:


> Nope, rubber roofing is composed of rubber (go figure), pan liners are not.
> 
> Sealer in no way, shape, or form, stops water. Read the label. Sealers allow vapor transmission by necessity.
> 
> ...


So basically I'm an idiot, but no offense right?

Both "rubber" roofing and shower liners can be and are made from PVC based synthetic rubbers, although roofing is sometimes made from EPDM as well (and I'm sure others, I don't know everything.) Either is acceptable for this application. The roofing is designed for flat roofs and standing water situations, not to mention constant exposure to sunlight and temperature changes, and comes in greater thicknesses.

As for grout sealer, it does aid in water resistance by filling the pores in the grout, but I didn't claim that sealer made grout waterproof. The sealed part went along with the whole *maintained* thing I was getting at. If grout degrades, water gets behind tile in significant quantities and can cause problems. That's all I'm saying.


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## JKRasku (Jan 7, 2007)

angus242 said:


> Not sure which seams you're asking about.


 
All of the seams in the kerdi fabric are sealed with thinset?


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## HS345 (Jan 20, 2008)

I didn't call you an idiot. If you feel comfortable using materials in applications other than they were manufactured for, then by all means, go ahead. 

You are simply wrong about the function of grout. Properly installed wall tile in a wet area is unaffected by water. Now, if water makes it through the substrate, and into the wall cavity in sufficient quantities, all bets are off. But as I said, in a properly constructed shower, this will not happen.

I really did mean no offense, we all gotta learn this stuff sometime. I built quite a few showers improperly before I learned the proper methods.


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## HS345 (Jan 20, 2008)

JKRasku, I'm not sure why you keep referring to Kerdi as a fabric, but that's not what it is. 

Yes, Kerdi seams are made with unmodified thinset. I know it sounds counterintiutive, but the science behind it is sound, and it works like a champ.


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## JKRasku (Jan 7, 2007)

HS345 said:


> JKRasku, I'm not sure why you keep referring to Kerdi as a fabric, but that's not what it is.
> 
> Yes, Kerdi seams are made with unmodified thinset. I know it sounds counterintiutive, but the science behind it is sound, and it works like a champ.


 
Ill call it membrane. I was doing some internet searching and saw a post on John Bridge forum that said he has seen water wick up under the membrane, but never any leaks. Do you normaly water test, and have you seen it wick before?


Ken


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## angus242 (Oct 20, 2007)

JKRasku said:


> Ill call it membrane. I was doing some internet searching and saw a post on John Bridge forum that said he has seen water wick up under the membrane, but never any leaks. Do you normaly water test, and have you seen it wick before?
> 
> 
> Ken


Yes, extensive tests have been done and water molecules will wick into the seam 3/8" but no further. That is why the MINIMUM overlap to each side of the seam is 2". And it's not the thinset that prevents moisture migration, it's the fleece that does.


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## HS345 (Jan 20, 2008)

I do not usually flood test my Kerdi showers, but I have in the past, and I have seen wicking, but the water doesn't penetrate more than about a quarter inch or so.


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## HS345 (Jan 20, 2008)

I posted this pic in another thread. In case you missed it, here it is again.

Note the wicking of the water up the fleece. I think if the seams leaked, this cardboard box woulda been toast.


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