Best backer option for Kerdi membrane

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Old 05-22-15, 08:06 AM
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Best backer option for Kerdi membrane

Hello y'all,

I am doing a shower tiled stall and am wondering what is the best backer to use with kerdi waterproofing membrane? With a little research I am leaning towards cement backer board. It seems that if there is an interior leak (inside the wall) well now that I think of it this is a major problem in itself....If there is a leak and I did use drywall then it will fall apart as where cement backer will not?

I guess my real question is what I started out with...What is the best backer for a shower installed with kerdi membrane?

thanks,

BV
 
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Old 05-22-15, 03:04 PM
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I have moved your thread to the tile forum for more exposure.

Why do you want to use Kerdi membrane? Is it because of the drain system you are using? If you go with cement backer board, you don't need kerdi on the walls. However you do need a pan liner for the floor. Tell us a little more about your intended build and what your process will be for both walls, floor and drain system.
 
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Old 05-22-15, 06:39 PM
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BV,

As you may know, Schluter recommends regular drywall as the backer for Kerdi. But some people just can't let their hands do that, so they use a concrete backer. No problem, that's not necessary, but it's fine. I tell people that I can make Swiss Cheese waterproof with Kerdi. Your choice.

The secret with Kerdi system is the drain and therefore how the floor and the bottom part of the walls are done. Many people use a hybrid method and apply 2 coats of liquid waterproofing for the walls above the Kerdi and change to a modified thinset. I've always stuck to the Kerdi system cuz I didn't care to switch just to just save $50-100.

Sounds like you've done some research and have a good idea how to do the entire job. If you do go with real concrete board, my favorite is PermaBase, although used lots of Durock too. I never cared for Hardie much, cuz 1. it really sucks the moisture out of the thinset and 2. it's not " so it creates transition issues. You should damp sponge the backer just before applying the thinset in either case.

It's important that you use good unmodified thinset, which may not be easy depending on where you're shopping for your materials. What brands are you considering?

Jaz
 
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Old 05-26-15, 07:49 AM
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I am using the Kerdi Membrane for waterproofing the enclosed shower area. I purchased the Kerdi Drain and 48 x 48 shower st.

My plan is to get the walls up. Still trying to figure what route to take...cement backer or drywall? If I go with the drywall what is the best type to use? Next, put up the membrane. Then install the drain and the shower st.

From watching the Kerdi videos it looks like this is the route to take? What do you think?
 
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Old 05-26-15, 12:02 PM
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Bob,

Regular drywall is what Schluter recommends and is all you need. Don't use greenboard if you have a choice. Green/blue/purple board is not as stiff as regular drywall and Kerdi makes it waterproof. Be sure to let us know what unmodified thinset you can get to install Kerdi and tiles.

The order of install is simple and as you said, except the drain goes after the foam base of course, but we know you knew that.

Is this a basic stall or is there a seat or other variations?

Jaz
 
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Old 05-26-15, 01:37 PM
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Thanks for letting me know Jaz.

There is a bench and a niche.
 
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Old 05-26-15, 03:10 PM
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You can build the niche anyway you want using drywall or concrete backer. The bench requires plywood but then you preferably cover it with concrete backer set into thinset. This way you can use the same unmodified thinset. If you Kerdi over ply, you'd have to change to a modified thinset wasting $$ and going against Schluter's rules.

Jaz
 
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