# Mastic in a Shower



## Anderson (Sep 7, 2009)

I have never used mastic for anything. All I know is it is kind of a glue. I have done several showers and used modified and unmodified thinsets. I have a new guy working with me and he has set some tile for me and is an expert by his description. 
So today we are getting ready to start a new shower after the old one failed. I sell the owner on a kerdi membraine etc etc.
As we are driving my guys says how its not gonna take him more than a day to set the tile in the shower with mastic. 
I don't remember exactly the reasons but a red flag goes off and I start telling him that its water soluable and that its organic and will grow mold.
Am I wrong do any of you guys use mastic in a shower. Are the other reasons for or against.
thxs guys


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## world llc (Dec 9, 2008)

i think you CAN use mastic on shower walls and ceiling, but you shouldn't... i don't

and if it's over kerdi, it will never dry... you HAVE TO use un-mod thinset.


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## thom (Nov 3, 2006)

I've used both mastic and thinset in showers, not on kerdi though. I've never used mastic on shower floors or any floors for that matter. The mastic dries and stays dry, no problems. Removing a tile a few years later is just as difficult with mastic as it is with thinset. Mastic does not re-liquify. 

Mastic allows you to go faster, it doesn't allow any slippage. It gets installed pretty thin so don't use it with a large/heavy tile. 

Maybe things work well because I live in a really dry part of the country.


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## ChrWright (Jul 17, 2007)

I would never use mastic in a wet location. Ever.


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## Paulie (Feb 11, 2009)

Anderson said:


> I have never used mastic for anything. All I know is it is kind of a glue. I have done several showers and used modified and unmodified thinsets. I have a new guy working with me and he has set some tile for me and is an expert by his description.
> So today we are getting ready to start a new shower after the old one failed. I sell the owner on a kerdi membraine etc etc.
> As we are driving my guys says how its not gonna take him more than a day to set the tile in the shower with mastic.
> I don't remember exactly the reasons but a red flag goes off and I start telling him that its water soluable and that its organic and will grow mold.
> ...


So what did the guy do when you told him about the orange sherbert cloth? :laughing:


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## Rich D. (Oct 14, 2011)

I recently tore out a shower that was failing. Only about 6 months old. The guy had no idea what he was doing. Let me elaborate. 

The membrane was up only 1 inch over the old cement board then sandwiched with another layer of wonder board. The curb was exposed wood. He sloped it all wrong. Clogged the weep holes, no pitch and he used wood he cut on a slope to slope the cement on the floor. AND LEFT IT IN... OH yeah and he used MASTIC on the walls.

So I had to rip the shower out. Well I was able to rip the 10"x14" tiles off the walls with my bare hands. And under the tiles there was a nice thick layer of black mold growing on the mastic. There goes up the plastic and the respirator on.

I would NEVER use mastic in the shower. 

I know they make a mastic for "wet' locations but like a kitchen backsplash not something that will get soaked. 

And for kerdi. Only unmodified otherwise it will never dry.


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## Lbpuente (Apr 16, 2011)

Never use mastic over kerdy. it will never dry.
and avoid using mastic on wet areas.:thumbsup:


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## world llc (Dec 9, 2008)

Rich D. said:


> And for kerdi. Only unmodified otherwise it will never dry.


TCNA tests show it will dry, but it will take up to 60 days under normal conditions. Schluter warned us even though the portland may cure in that time, the latex may not coalesce sometimes causing it to leach into grout.

bottom line: use dry set


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## Rich D. (Oct 14, 2011)

world llc said:


> TCNA tests show it will dry, but it will take up to 60 days under normal conditions. Schluter warned us even though the portland may cure in that time, the latex may not coalesce sometimes causing it to leach into grout.


I also heard that. I'll just stick to the unmodified (dry-set) like they recommend.. works well.


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## tileman2000 (Feb 14, 2011)

If they think using mastic in a shower is acceptable, it's time to find another tile installer. I'd be surprised if they even knew what Kerdi is.

Not to mention, thin-set is much cheaper in price.


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## Rich D. (Oct 14, 2011)

world llc said:


> good read:thumbsup:
> 
> where in jersey are you?



I'm over in Hudson county :thumbsup:


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## Anderson (Sep 7, 2009)

Had a talk with the guy today didnt go to well as he's mean doing tile for a while and seems to think his way is fine although he agreed wont work on kerdi. 
So I had to give him the old "my way or the highway"


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## kevjob (Aug 14, 2006)

I dont even use mastic on wainscoting outside the shower, mastic IS NOT FOR SHOWERS!


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## TNTRenovate (Aug 19, 2010)

The only time I use Mastic is on a kitchen back splash. In and out in a few hours. Love the stuff!

It is not designed for showers. It may "work", but it won't last and will mold and mildew.


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## Lavezzo Const (Oct 27, 2011)

I have used mastic in showers but never over kerdi, but on top of Durock or hardi. Id go with the white thinsethttp://www.lavezzoconstruction.com


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## Anderson (Sep 7, 2009)

I had it out with him today and to clarify his position is that he can use mastic when setting 4x4 porcelain, and epoxy grout. 
I understand what he is saying, that basically no water can get through, but then who ever built a shower with the idea that water can get through.


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