# Kerdi



## Jer (Nov 13, 2008)

Hey guys,
Took the advice of alot of you and invested in Kerdi moisture barrier for my personal bathroom remodel. Tried to install it over the hardi backer today with unmodified thinset and a 3/16 v-notched trowel as recomended by my supplier. It just isnt sticking well at all and especially on the ceiling. Is there a different adhesive I should be using?
Any input appreciated a bunch!:confused1:


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## Lackey (Nov 3, 2009)

how quickly are you spreading your thinset and setting the membrane? could be that your mix is too dry or the hardi backer is sucking the moisture out before you get a chance to set the membrane.


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## angus242 (Oct 20, 2007)

Use a quality non-modified; Mapei Kerabond, Laticrete 272 or Ditraset.

Mix the thinset as thin as you can while still able to hold a trowel line.

Moisten the Hardi before spreading thinset. I use a spray bottle set on fine mist.

Key in the thinset on the substrate _before_ troweling your grooves.


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## ApgarNJ (Apr 16, 2006)

I installed mine today on that job angus, I am hoping it is stuck by tomorrow. How long does it take to stick, it should be stuck good enough that you can pull on it, it won't come back off? I am waiting to tile until tomorrow. I attached the kerdi and then worked on the tile floor. The kerdi is stuck to the walls but I was afraid to pull on it to test it. I mixed my un-modified thinset that the schluter dealer recommended, pretty wet, it was sloppy and messy but not too runny that I couldn't trowel it. I used a 1/4x 3/16 v notch. couldnt find the 1/8x1/8 square. They didn't have keribond and I wasn't drving all over south jersey looking for it. I already have an hour and a half drive to get to this job. 

How long does it take for the thinset to really make a strong bond with the kerdi. I hope I don't have a mess on my hands tomorrow. The kerdi was easy to smooth out with a grout float and I made sure I didn't push out too much, very small amount was at the edges if any.

I did test the backing and make sure it was embedded in the back of the kerdi like they recommend. If it doesn't stick. I'm ripping it all out, cutting the drywall out and putting 1/2 hardi up. I can't afford on this job, to buy more and redo the whole thing. I can't imagine making the thinset any wetter than I did. It was already slopping off the edge of the trowel putting it up. . 

The place didn't have any kerdi-fix in stock. I've read on Jbridge where you can use an equivalent caulking/sealand at the tub. I can't imagine on a tub surround with a large lip and the kerdi down to the tub that it would ever leak an inch upwards after it's been sealed. The tile also gets sealed once it gets installed.


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## JazMan (Feb 16, 2007)

Don't pull on a corner, it proves nothing cuz you're applying about a gazzilion times more pressure than in a real installation, plus it's a different kind of pressure. Tiles applied to it apply pressure of their weight over the entire size of the tiles. 

By your description of the consistency of the thin set, it sounds to me is was a bit looser than ideal. Did you moisten the wall board first? I usually don't need to if I'm going over wall board, but it can help. Next time try a cement finishing trowel instead of the grout float. It would seem to me it would be kinda sticky to work out the air.

Jaz


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## ApgarNJ (Apr 16, 2006)

the grout float was a smooth one, not a black rubber one. It glided just fine. I was told by angus to make it wet enough to hold and edge when troweled. Which it was. it wasn't too runny like it could pour out on the ground and all over. just runnier than it would be if i were setting tiles.

what do you think about a kerd-fix alternative. I was going to use a Geocel 2300 clear sealant/adhesive as this stuff sticks to just about anything and it's worked great in other applications. I have to go way out of my way driving down to this job to get to a place that stocks kerdi-fix. I already ran the kerdi past the drywall and down to the tub surface. It's almost an inch past where any water would leak between the flange and the drywall. 

Tiles on the wall are going to be 6", so there is no way the tile would be in jeopardy of failing. 

I won't pull on anything tomorrow then if the tiles hold, they told. There weren't any air bubbles. it smoothed out just fine.


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## angus242 (Oct 20, 2007)

Sounds a case of the virginities. :laughing:

Jaz said it all about the Kerdi. :thumbsup:

Do you have the Kerdi tucked behind the tub flange or over it?

A little German birdie once told me 100% silicone would work. :whistling


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## ApgarNJ (Apr 16, 2006)

thanks angus, lol

yes, it was a virgin kerdi party today. I do like it though. I put the kerdi Over the flange. and the kerdi runs to the ceiling. I ended up with 1/4" hardie on the floor though, this shower is rarely going to get used and even in the summer, the outdoor shower gets used a lot more than this one will. 
I should have the shower/tub all tiled up tomorrow. 6" tiles in a brick pattern. no niches, no shelves. I haven't done a shower without those items ever. so it should go faster. only have to cut around the tub pipe, valve and shower supply.


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## Jer (Nov 13, 2008)

Sounds like I have company in this boat....Lackey I used thinset for my first time ever today so it was going on slow but I was doing a small section at a time and then bracing it (ceiling) in an effort to stick it while the thinset was wet.
Angus I am using Mapei unmodified kerabond tile mortar but I didnt know about spraying water on the hardi board first and my mortar was mixed to about the thickness of cake frosting, maybe a hair thinner. Do you spray that water liberally or do you have to be careful not to over wet it?
Apgar mentioned Kerdi Fix...what is that and should I get some? Is there any other product that would be better or should I say a safer bet for a rookie trying to do a ceiling? I sure dont want to spend the rest of my life wondering if a tile ceiling is gonna come crashing down on my naked arse!


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## angus242 (Oct 20, 2007)

Jer said:


> Angus I am using Mapei unmodified kerabond tile mortar but I didnt know about spraying water on the hardi board first and my mortar was mixed to about the thickness of cake frosting, maybe a hair thinner. Do you spray that water liberally or do you have to be careful not to over wet it?
> Apgar mentioned Kerdi Fix...what is that and should I get some? Is there any other product that would be better or should I say a safer bet for a rookie trying to do a ceiling? I sure dont want to spend the rest of my life wondering if a tile ceiling is gonna come crashing down on my naked arse!


It's hard to say how thin I mix my Kerabond. I do it so often, I go by feel. Like I say, thin but still able to hold your ridges. When you are smoothing out the Kerdi, you will see it change color as the thinset penetrates the fleece. That's how you know you got the air out and have appropriate coverage. 

Kerdi-Fix is Schluter's sealant. You use it to connect the Kerdi to the tub flange. It's not cheap...$25-ish per tube. Some recommend 100% silicone instead. 

Like Jaz said, because you can peel Kerdi back after installing does not mean it won't adhere. A ceiling is a bit different. I would wait a day before installing the tile. If you're truly concerned, just use a liquid membrane like Hydro Ban instead. You can just overlap it onto the wall Kerdi.

Once you install the ceiling tile over Kerdi and it's cured, just tap on the tiles. If you hear a hollow sound (like you would on a floor tile that isn't properly adhered), I'd wear a hard hat when showering :laughing:


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## HS345 (Jan 20, 2008)

Silicone does not seem to stick well to Kerdi. If you want a Herr Schluter acceptable substitute, it has to be a urethane based sealant. 

Kerdi Fix is really not as expensive as it seems, for the amount you need. One tube will do three or four tub surrounds, and it keeps well in the tube. When I'm done with my Kerdi Fix for the day, I squeeze a little bit out the end of the tip and let it dry. Next time when you need some, pull the little plug out and you're good to go.


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## Paulie (Feb 11, 2009)

It's official, it's virgin Kerdi week. :laughing:

Here are some Virgin Kerdi questions.

#1. Using Denshield wallboard, what do I fill the seams with? I assume the mesh for tile for tape but what do I use for mud?

#2. My supplier delivered 2 sacks of Kerdi bond. Do I use that for setting the curb and membrane?

#3. Kerdi bond mortar for setting the tile or just regular thinset like always?

Maybe I should start posting at the DYI site. :laughing: Just in uncharted territory here.


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## ApgarNJ (Apr 16, 2006)

I tiled the tub surround today. kerdi was well adhered. 1000% silicone stuck very well to the tub/kerdi connection at the bottom.

6x6 tiles offset pattern. 

one cool thing about the kerdi on a tub is if you start with the short walls and wrap it around the corners, all you need is one row vertically in the middle of the 60" wall. it's the perfect size, and you kerdi-band the butt seams. 

I thought the build up would be too much but it wasn't. Not using kerdi-band would have built it up a lot.


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## angus242 (Oct 20, 2007)

paulie said:


> It's official, it's virgin Kerdi week. :laughing:
> 
> Here are some Virgin Kerdi questions.
> 
> ...



WHOAAAAAA!!!!!!!!!!

1) Why are you using Kerdi over DensShield? Membrane over a membrane? :blink:

2) What the heck is Kerdi bond? :blink:

3) See #2. :blink:

Unless you are installing DITRA over plywood, ALL OTHER SCHLUTER MEMBRANES AND FOAM SHOWER COMPONENTS USE NON-MODIFIED THINSET TO BE INSTALLED (per Schluter). TILE OVER DITRA/KERDI IS ALWAYS NON-MODIFIED.

_Special situations may occur when using moisture sensitive stone or glass over a Schluter product. Call them for recommendations_


OK, I assume you meant _Mapei Kerabond_ for your non-modified thinset. :thumbsup:

If you have already hung the DensShield, save yourself some cash and just get a bucket of liquid waterproofing (Hydro Ban, RedGard) and use that over your seams. Now you're done. :thumbsup:


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## ApgarNJ (Apr 16, 2006)

Angus, what's the main benefit of kerdi over just doing what you just stated. Denshield with hydroban or redguard? not as good?


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## angus242 (Oct 20, 2007)

DensShield already has a waterproof membrane on its surface. You only address the seams and screw holes with some kind of waterproofing.

I believe it comes down to preference. A fabric membrane doesn't take any sort of minimal applied thickness to become waterproof. However, they are usually more expensive and you have to use them over all parts of the walls (ceilings) in the wet location.

Liquid membranes can be applied to the seams/screw holes of wall boards like DensShield. You would use the liquid over the entirety of CBU. Also, you need to apply a minimal thickness to achieve a waterproof perm rating. This can take up to 3-4 coats in certain areas/cases. You also have to wait for it to dry in between each coat. 

There is no "best". It's what _you _feel most comfortable applying. Cost of each material can make a difference and obviously availability. And finally the method at which you can be most efficient with. 

I have criteria for what materials/methods I use. A complete bathroom remodel would be different than just a shower redo.


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## HS345 (Jan 20, 2008)

ApgarNJ said:


> I tiled the tub surround today. kerdi was well adhered. *1000% silicone* stuck very well to the tub/kerdi connection at the bottom.
> 
> 6x6 tiles offset pattern.
> 
> ...


Wow, 1000% silicone?  How do they get it all inna tube? :laughing:


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## Paulie (Feb 11, 2009)

OK, I assume you meant _Mapei Kerabond_ for your non-modified thinset. :thumbsup:
*
If you have already hung the DensShield, *

Nope. But I have purchased the Kerdi. 

So just regular old wallboard? Really?


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## HS345 (Jan 20, 2008)

paulie said:


> OK, I assume you meant _Mapei Kerabond_ for your non-modified thinset. :thumbsup:
> *
> If you have already hung the DensShield, *
> 
> ...


Yep, just regular old drywall (unless it's a commercial steamer).

You can download the installation handbook HERE.


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## angus242 (Oct 20, 2007)

Or if you want to "upgrade" the wallboard, use DensArmor :thumbsup:


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