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Old 09-13-2017, 08:08 PM   #1
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Mapei Aquadefense for steam shower vapor barrier?

Hi, I'm hoping someone can save my failing eyesight from staring at this tiny phone screen for 12 hours and help me answer this question. I've already talked to the very nice people at Mapei customer service, but unfortunately their tech support center is still lights out in Florida after hurricane Irma. Don't they understand I have tile to install??!

We're installing a 5x7 steam shower in our rehabbed 1870's farmhouse (swoon, right?) and our guy likes AquaDefense for the job. Over Redgard. Over Kerdi or Noble (which he's never worked with.) At first we thought he was showing his incompetence since Mapei's installation guide specifies using an additional vapor layer in steam shower applications, which he denied. Then while trying to convince him he HAD to switch gears and go with Kerdi/Noble/Redgard for vapor control, I find THIS on Mapei's (new?) 2016 install guide:

"ASTM: E-96 Method E, meeting requirements of <0.5 perms"

What gives?? Everything, and I mean EVERYTHING, I've read online about AquaDefense says it requires an additional vapor barrier in steam showers. But if this information is correct, it's even less permeable than Kerdi. Than everything except for Noble! Did they change their formula to match Redgard? Is it a typo?? I'm about to gouge my eyes out, please Obi-Wan, you're my only hope!

Lisa in Riverside
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Old 09-13-2017, 09:17 PM   #2
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Aquadefence pdf

Limitation states '' In steam rooms, a vapor barrier is required in conjunction with
Mapelastic AquaDefense'' , so it clearly says it needs a vapor barrier which implies the aquadefence is not one .

Recommended products from Mapei to be used in a steam shower , follow the link below

Installing tile in a steam shower

Knowledge -- something you cannot undo once you learn about it --
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Old 09-13-2017, 10:06 PM   #3
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Welcome, Lisa.

Yep, pretty confusing, even the wording in various places on that same page on MAPEI's website.

I started a great long dissertation on permeance testing and requirements in the tile industry, but that's better suited to a discussion in the Hangout. Suffice to say here that the requirement for a permeance rating of 0.5 or less applies only to continuous use steam showers as noted in the TCNA Handbook. Your residential shower would not technically require that level of vapor management, but who's to say you couldn't use it continuously?

I would recommend a sheet-type A118.10 membrane for such a residential shower and would further recommend the USG Shower System membrane, which actually meets the requirement of less than 0.5 perms anyway.

There are other considerations for steam showers that don't apply to regular showers and I hope you've done as much research on those as you have on the permeance of your waterproofing membrane.

My opinion; worth price charged.

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Old 09-14-2017, 08:51 AM   #4
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The "catch" with the liquid waterproofers, like AquaDefense, is that they have to be installed to a proper thickness. It's not easy to get it that thick. If it's not the required thickness then the ratings on the spec sheet don't apply.

I would ask the contractor a few more questions. "How thick does the AquaD have to be?", "How do you determine how thick it is on the wall", "How many coats do you usually do?"

The answers to those questions will tell you if the contractor knows what he's doing.

But I agree with CX about a sheet membrane. I think Mapei has one of those.
Jim Upton
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Old 09-14-2017, 02:06 PM   #5
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While the advice above is good, AquaDefense is now rated <0.5 perms which meets the industry requirements for a steam shower. We made that change last year so you will likely still find outdated references that contradict it, sorry about that. It doesn't require an outrageously thick layer unlike some competing products, we tested it at 20 mils dry film thickness which is less than the thickness of a credit card. Two heavy coats or, ideally, three moderate coats should get you there. Sorry you couldn't get through, if you left a message you likely have had a call-back by now.

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