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Unread 04-16-2021, 03:45 PM   #8
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 14,423
Surface bonded membranes have been around since the 1980's, have millions of installations, and are not new. They work when you install them properly, and it isn't really very hard but you do need to do your research. The advantage is that the ENTIRE shower, is waterPROOF just beneath the tile, so, that gives you some peace of mind about what might be used underneath it, as, at least from the top, water won't get to it.

In a cursory look at some of the 'systems', you'll get the impression that their foam pans are a requirement...that is not true. The membrane will work just fine over deck mud as well, and that allows for more easy customization. Another advantage to the system is that you only need ONE mudbed, as the drain does not need or have weepholes, and the liner is designed to accept thinset to bond the tiles in place directly. FWIW, cbu dust is carcinogenic, the boards are heavy, fairly small (4x8' sheets are available, but a pain to use and get home in one piece!), and, while not damaged by being wetted, are NOT waterproof.

Each manufacturer lists acceptable materials that can be used underneath their materials, and at least for Schluter, that includes plain drywall. To skip a step, they do make tileable, foam panels that, can be screwed in place, or, over concrete, applied with thinset on walls that can also help plumb the wall while flattening it that can be a huge time saver. You need to waterproof the seams and screw penetrations.

IMHO, liquid applied waterproofing, while it can work, and may be the best for some circumstances, is more finicky as it takes a fair amount of experimentation to get the two coats, each the required thickness, without pinholes, runs, or voids. Too thick is as bad as too thin, and it's really hard to get the minimum thickness...it's not like paint where you can just keep adding coats...
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Jim DeBruycker
Not a pro, multiple Schluter Workshops (Schluterville and 2013 and 2014 at Schluter Headquarters), Mapei Training 2014, Laticrete Workshop 2014, Custom Building Products Workshop 2015, and Longtime Forum Participant.
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