Not confident about kerdi adhering to wall [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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01-29-2007, 08:59 PM
Well I started my first my first home improvement shower project over Christmas. My wife found the Kerdi system and it sounded like the perfect system. Especially for someone with little experience and concerned about waterproofing. I bought the Kerdi Shower Book by John Bridge online and have read through it several times. My main question at this point in my project is around the Kerdi and thin setting it to the wall. I applied 2 vertical sheets yesterday using unmodified thin set and I don't feel confident that it adhered to the wall enough. There is one small area on the inside of my niche that I can tell did not adhere at all. I found one other approximately 4 sq inch area that I can tell did not adhere. My concern is that the Kerdi can be fairly easily pulled away from the thin set and dry wall. What would keep the tiles that will go over the Kerdi from just pulling the whole thing down?

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01-29-2007, 09:15 PM
Walt, tell us what brand of thinset you were using.... Some of the unmod's aren't very good... I took Mr. Bridges advice from the start and use Versabond, a lightly modified thinset... Over a dozen Kerdi showers later, and not a single issue. You also need to mix it up a little runnier than usual, it'll help with the smoothing. Don't try to peel it the next day, it wont get it's full bond for 2 or 3 days. I've tiled over it right away without any issues though. :)

01-29-2007, 09:25 PM
Alex, I used Custom Blend - Standard Thin Set Mortar from Home Depot. I didn't mix it on the runny side. I figured I better stop and ask questions since I was only about a third into the Kerdi. I need to evaluate whether to pull it down and start over or what.

VanTines tubntile
01-29-2007, 10:08 PM
walt you will definatly want to try another brand of thinset try mapai's kerabond I have had the best of luck with it.. and you definatly will want to mix your mud quite a bit more soupier not so much as to seperate the paper from if going over sheet rock.... good luck with it

01-29-2007, 10:34 PM
Welcome, Walt. :)

It's not so much the brand of thinset you used as the quality, Walt. CustomBlend is Custom's bottom line and is simply not a useful product in my opinion. We love Custom dearly. They are even one of our sponsors. They make a lot of very good products, but that is not one of them. I also do not recommend their MasterBlend in showers.

In the Custom line, you can use the PremiumPlus unmodified or, as it says in your Kerdi eBook, use the VersaBond, even though it's not recommended by Schluter. The Versabond is easy to use and will make life more pleasant for you.

You can also find Laticrete 317 in some Lowe's stores. That's a good un-modified thinset to use with Kerdi.

Job's suggested pookey is good, too.

If you can find a source for the new unsanded thinset that Bostik is making for Schluter under the name Kerdi Set, that would be my very first choice. I've not had occasion to use it yet, but the reviews are very good.

Might look through that eBook again, too. I think maybe you missed a couple of the more subtle points in there. :)

My opinion; worth price charged.

01-30-2007, 02:05 PM
I'm just slightly going to sidetrack Walts thread here... I dont understand the use of UNmodified thinset under Kerdi. While the Kerdi may not allow the latex modifiers in Versabond to dry well, the sheetrock you're putting it on certainly will suck up the moisture and dry it out.

Herr Schluter's Ditra says use an appropriate mortar for the substrate, (generally a latex modified mortar) and an UNmodified between Ditra and tile.. Why not the same for Kerdi?

I still use Versabond for everything. Hell, I even butter my bagel with it in the morning.

01-30-2007, 02:20 PM
That makes logical sense to me.

So, grey or white Versbond for the bagel?? I would think that White tastes better :shrug:

01-30-2007, 02:25 PM
Mastic is better for bagels.... Holds it together better.. :yeah:

01-30-2007, 02:47 PM
Herr Schluter's Ditra says use an appropriate mortar for the substrate, (generally a latex modified mortar) and an UNmodified between Ditra and tile.. Why not the same for Kerdi?It is the same for Kerdi, Alex. Unmodified thinset is appropriate for use over sheetrock. Works just fine.

In fact, plywood and OSB are about the only common building materials a fella would be likely to wanna install Ditra or Kerdi on which would require anything but unmodified thinset, and you're not s'posta be installing Kerdi over them two. Those materials require a thinset meeting A118.11, which is a latex or polymer modified pookey by definition.

That said, I use VersaBond. And one of these days Herr Schluter is gonna tell everyone that it's OK. Oh, yeah, he really is. :)

My opinion; worth price charged.

01-30-2007, 02:50 PM
I'm not ready to put any on a bagel, but I'm starting to really like the smell of MegaLite. It's a good thing I just set my last few glass tiles down. Next up is SpectraLock. I already know it doesn't smell as good.

01-30-2007, 03:59 PM
In fact, plywood and OSB are about the only common building materials a fella would be likely to wanna install Ditra or Kerdi on which would require anything but unmodified thinset,

Learn something new every day... :nod:

I'm still sticking with my Versabond. :tongue:

01-30-2007, 07:33 PM
I appreciate all the feedback! Even the jokes. I need a few laughs as I regroup. I guess I took the comments about using unmodified too seriously and I accepted the first and only unmodified thinset I found at Home Depot. I also think I didn't make the thinset wet enough. I feel confident it will go better when I try it again. I will likely use the VersaBond since I have used that before on a floor and know that it is available.

I'll check back every so often and also explore the site for helpful info. I'll let you all know how attempt number 2 goes. May take a bit to get back on track since I am doing this in my spare time. Thanks! :wave:

03-10-2010, 05:15 PM
Wow, just found this posting, thought I had done my research....

Used customblend instead of the Versabond I normally use and love (and have quite often thought if this stuff was just as tasty as it looks I could work non-stop!!!!) I did recently switch back to Versabond for tiling..

took the spec. too seriously.....bought the only one I could find at Home Despot that was unmodified...but I live in desert and found my Durock was thirsty! skinning for sure, of course I got better as I went along...but had to mix the customblend runny.

I have quite a few bubbles, mostly are quarter size some even dime or screw head size..imagine that.

The largest about 2" by 2"...Do I really have to cut them open, seems rather extreme, can't I inject something?

Are bubbles on the floor so critical?


03-10-2010, 05:43 PM
I discovered a 2" x 3" bubble in my Kerdi. I cut an "X" over the bubble area, carefully peeled back the 4 triangles, spread the thinset, closed it up, combed it lightly with the straight edge of the trowel making sure to get all air and excess thinset out, then patched over it with a piece of Kerdi. Was quick and easy and I see no reason for it to leak.

03-10-2010, 06:21 PM
Yep, that is a great quick method of fixing that type of issue.