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Unread 01-05-2010, 12:46 PM   #1
dawedler
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Shower Project: Using Kerdi with HardiBacker

I am rebuilding my shower and have some questions regarding Kerdi membrane and HardiBacker board. I have a recessed mortar shower floor that does not have a liner (I guess the builder didn't think it was important). I plan to install HardiBacker on the walls and a Kerdi drain and Kerdi membrane. Then tile the floor and walls.

Here are my questions:
1. Thinset type: Kerdi recommends unmodified thinset to apply the membrane. HardiBacker recommends modified thinset. Can I use Kerdi with HardiBacker? If so, what thinset do I use (modified, unmodified, acrylic, latex)? Is HardiBacker compatible with Kerdi or should I use a different backer board?

2. Drain Install: I need to dig out my old drain (just a standard drain with no weep holes) and install the Kerdi drain. I plan to break up the concrete around the old drain and then mortar in the Kerdi flange rather than redoing the whole pan. I this correct. I will use a concrete patch to make sure there is a smooth pitch to the drain. Is this correct?

3. Kerdi Membrane: Can I install Kerdi on the floor and a foot or so up the walls and then cover the rest of the walls with RedGuard (or some other paint on waterproofer)?

Thanks for any advice you can offer.

Doug
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Last edited by dawedler; 01-05-2010 at 01:01 PM.
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Unread 01-05-2010, 01:09 PM   #2
Shawn Prentice
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1. unmodified under kerdi unless going over ply or osb. You can use hardi, but you really only need drywall per Schluter's instructions and recommendations.

2. You propose to leave the old pan in place and just remove the mortar around the drain? You need to take out the old mud bed.

3. Why? I wouldn't do that. Schluter wouldn't warranty that either.
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Unread 01-05-2010, 01:34 PM   #3
Splinter
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Schluter does require unmodified, but finding a quality one locally may be a challenge. I and others here use Versabond. It will have NO problem drying over the Hardibacker, even the Kerdi-Kerdi overlaps will be fine. Versabond is available at any Home Depot.

You could sink your Kerdi drain into the existing pitched floor, but the cold joint between the new and old mortar may be an issue, even if treated with a thinset when placing the new mortar. Also, how smooth is the existing floor after old tile removal? You'd be better off bonding a new mortar bed to the old one. It doesnt have to be so thick over the existing concrete.

Forget the RedGard.. It'll void any warranty, it's not saving much money or time, and unless you get the RedGard applied thick enough, you might have issues with water getting behind the Hardi, and eventually the Kerdi'd pan.
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Unread 01-05-2010, 01:38 PM   #4
jgleason
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I wouldn't bother with the Hardibacker at all. Just use regular drywall and Kerdi over it. Kerdi works perfectly well with drywall as a substrate.
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Unread 01-05-2010, 01:56 PM   #5
dawedler
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The floor was quite "pitted" after I removed the old tile. I smoothed it out using Top N' Bond Concrete Patcher. Then I began research on drains and decided that the original drain needed to come out since there is no pan liner. It is just a standard 4" PVC drain that is glued to the pipe. It is raised about 3/8" above the pan.
I came across the Kerdi drain and decided to go with that. Should I just break up the whole pan and repour the whole thing? I was thinking that the Kerdi membrane would seal any cold joint issue?
I am a novice at this whole thing so I am trying to keep it simple.

Regarding HardiBacker for the walls, that was my original plan before discovering Kerdi. I guess I could return it and just get drywall. I guess it is extra peace-of-mind protection for someone who has never used Kerdi.
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Unread 01-05-2010, 02:03 PM   #6
dbarberic
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My experience as a first time a first time Kerdi user.

I used 1/2" Hardi Backer because I started building my shower before the Kerdi kit arrived and I did not fully understood how Kerdi worked. I originally thought it was a glorfied pre-sloped pan. Plus, I like the idea of "overbuilding" anything I do.

They are right. If I could do it all over again, I'd go with drywall. So much easier.

The big problem with Hardi Backer is that it just sucks all the moisture out of the thin set which causes it to dry out very quickly before the Kerdi can be worked into it. I even pre-moistened the Hardi with a water spray bottle, but it did not help at all. The sprayed areas would dry in less than 30 seconds. I had so much trouble with the Kerdi trying to install it to my Hardi backer that I ended up ripping down my first attempt the next day and doing it all over again. When I ripped down the Kerdi I found that it never adhered properly because the thin set dried out before the Kerdi had a chance to adhere.

When I ripped the Kerdi down from my first attempt, a skim coat of thin set was left on the Hardi Backer. This helped so much for my second attempt because the skim coat acted as a barrier to prevent the Hardi Backer from sucking out all of the moisture and causing the thin set to prematurely dry out.

So... long story short... don't use Hardi if you don't have to. If you choose to do Hardi Backer, you will have much better results if you do a skim coat of thin set first and then install your Kerdi 24 hrs later.
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Unread 01-05-2010, 02:11 PM   #7
Shawn Prentice
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Quote:
I am a novice at this whole thing so I am trying to keep it simple.
That's the thing. The right way is rarely the simplest.

Quote:
Regarding HardiBacker for the walls, that was my original plan before discovering Kerdi. I guess I could return it and just get drywall.
You can use the hardi, just give it a "drink' first with a damp sponge before applying the kerdi (So, the dry hardi doesn't suck the moisture out of the thinset.) You could have the hardi installed by the time you return it and get the drywall.

Quote:
I guess it is extra peace-of-mind protection for someone who has never used Kerdi.
Don't worry about it. Download a copy of their shower system installation handbook, follow the instructions, ask questions here if anything doesn't make sense.
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Unread 01-05-2010, 02:15 PM   #8
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Here you go:

http://www.schluter.com/media/brochu...book-ENG09.pdf
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Unread 01-05-2010, 02:26 PM   #9
dawedler
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Quote:
That's the thing. The right way is rarely the simplest.
This is what I will tell my wife when she complains that this project is taking to long. To think this started out as a just re-grouting the tile.

Thanks for the shower install handbook.
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Unread 01-05-2010, 02:34 PM   #10
dawedler
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Question:
Where is the best place to purchase Kerdi? I live in Orlando and I am having difficulty finding a local supplier?
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Unread 01-05-2010, 02:35 PM   #11
Shawn Prentice
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The big orange box store, some places online. Check with your local tile contractor suppliers or call Schluter and see who the distributor is there.
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Unread 01-05-2010, 02:52 PM   #12
dsoniat
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Doug, (just a DIY'er here),

my HD (in Tampa) didn't carry kerdi and special ordering through them seemed cumbersome.

i ordered mine from www.tile-experts.com/


took a couple days, but I was nicely satisfied. will put my first piece up over hardie tonight....
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Unread 01-05-2010, 03:18 PM   #13
dawedler
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HD here in Orlando had know idea what I was talking about when I mentioned Schluter Kerdi. I'll check out tile-experts.

@dsoniat
Let me know how the install goes over Hardie.
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Unread 01-11-2010, 04:59 PM   #14
dawedler
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Doug's Shower Remodel - help

I am in the midst of a shower remodel and need some advice. It started out as just a simple re-grout project. Then I discovered mold and termite damage in the knee wall so I have torn everything out down to the studs and pan. I have re-framed the knee wall and now I am stuck.

The original pan is recessed below the concrete slab. It has a two inch high rim of mortar surrounding it that is about a 1/2 inch thick. Wonderboard sat on this rim. The pan does not appear to have a liner and the drain is just a basic single stage drain with no weep holes.

I am trying to figure out how best to approach the pan?

My plan is to install hardibacker on the walls. Dig out the old drain and install either a kerdi drain or divot type drain. Then apply fabric to the corners and use hydroban to waterproof.

Questions:
1. How do I remove the old drain?
2. How should I approach the pan? (leave the rim, slope mud up past the rim to the board)
3. How about my approach to the membrane? (I have considered the kerdi system but then read the thread by gueuzeman and thought it seemed viable).

Right now I am stuck until I figure out the drain and pan. (I will post some pictures of the pan. Thanks for any advice. Doug
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Unread 01-11-2010, 05:03 PM   #15
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Got some pics? you have to make 2 postings then you can put pics in. So tell us a little more. A decision on which waterproofing method will be very helpful in giving step by step instruction. I vote kerdi.
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