Problem with kerdi adhering. [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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02-19-2010, 07:47 AM
Ok so I buy John's kerdi book call Schluter ask them what type of unmod thinset to use and they tell me mega bond so I mix it up put the kerdi up on the walls around a deck tub surround forget about it for a few days go back today and the edges of the kerdi arent sticking. I pull on the edges and the kerdi comes off with what I would call minimal pulling to me it feels like it anyhow. When I put the kerdi up I made sure I put thinset about 2 inches past where the kerdi was going to on the wall because i wanted to make sure Kerdi stuck. This is my first kerdi shower and bath. Now I'm afraid to tile over it for fear tile will just pull the kerdi down over time. Should I pull the kerdi down and start again? Can I clean the thinset off the kerfdi I used and use it again if thats what you suggest this junk ain't cheap. or should I just try to pull the kerdi back and thinset just where it is coming off at the edges. I bought and used the kerdi 1/8x 1/8 notch trowel and thats what I used to apply thinset. Any help would be appreciated.

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02-19-2010, 09:42 AM
It does take a few days for unmodified to cure hard, but if it has been a few days since you put up the kerdi then you may have a problem. How about a few more details.
1.are you putting the kerdi over drywall? thick was the mortar you used on the kerdi of were you pealed up the kerdi
4.test the mortar you used. mix up a little ball to play-doh consistency, then wrap it in plastic and leave it for at least a day to see if it hardens up.

Three things come to mind right now. First, maybe the mortar hasn't cured yet. Kardi will actually peal off untill the mortar sets really hard. Second the mortar dried out too soon. This can happen if you go over hardi backer with dryer mortar, or if you just squeezed out too much mortar when you did the kerdi.
Third, and probably least likely, you got bad mortar.

02-19-2010, 10:19 AM
Is the Kerdi pulling away from where it is set to plywood?

Unmodified thinset is not the right choice to stick to plywood. Did you cover your framing with CBU?

John Bridge
02-19-2010, 12:02 PM
Hi Jody, :)

It's possible you squeezed all the thin set out from behind the Kerdi at the edges. I've done it. ;) The other thing is not having the thin set loose enough and allowing it to "skin over" before applying the membrane.

02-19-2010, 04:50 PM
Is the Kerdi pulling away from where it is set to plywoodplywood ? where ? :scratch:

I like using MegaBond with Kerdi, it' drys nice. I also suspect you might have flat trowel and pushed out too much thinset at the overlaps.

I like to let my thinset come out the over lap, then flat trowel most of it off and then hit it with a sponge the opposite way so the thinset holds the edge down and drys nice.

Houston Remodeler
02-19-2010, 05:46 PM
Try using one of these to smoosh the kerdi to the thinset. This way you can't squeeze out all the thinset.

02-19-2010, 06:42 PM
Ok guys here are some pics.

Brian in San Diego
02-19-2010, 06:48 PM

That kerdi is not imbedded properly. It looks like maybe the thinset was too stiff or you applied it and let it skim over before the kerdi was put over it. Or it's possible you didn't apply enough force to get it into the thinset. Even with the thinset not quite loose enough if enough force is applied then you wouldn't see the ridges that are so prevalent in your photos.

Plywood is not an approved substrate for kerdi. I know JB does it but Schluter frowns on it.


02-19-2010, 06:49 PM
Answers to some of the questions the kerdi was applied to drywall and the deck was hardibacker but walls are drywall I mixed the thinset to the consistency of probably between peanut butter and soft ice cream. it was not put on plywood not sure where that came from. I flat troweled it afterI stuck it to the wall not sure if I did it too much or not maybe.

Now my question is by what you see should I pull it completely off the wall and start again. and try to clean the kerdi off? or should I leave what is stuck on the wall peal back and try to thinset it again? Thanks guys sorry about the pics are not the best they are from an iPhone

02-19-2010, 06:57 PM

Thanks, maybe I didnt mix it loose enough :bonk: maybe it was too thick. Ill scrape it off and try again with not as thick thinset. Think I can use the kerdi again?

02-19-2010, 07:02 PM
Hey Jody,

If the Kerdi comes off the wall intact (like in your photo) you can use it again. If it pulls the fleece off any part of it while you are removing it I would not use it again.

Try the consistency of a milkshake - works for me. :D

02-19-2010, 07:07 PM

Thanks will do. No a question just popped up in my mind when you said the fleece is there a side that is supposed to go againsed the wall and a side that is supposed to go against the tile? does it matter? Because the side that is against the wall is the side that doesnt seem to be fleece the fleece side seems like it is the side that would be against the tile. should I flip it?

02-19-2010, 07:11 PM
Both sides are the same so no worries there. Definitely looks like the thinset was a bit too stiff and skinned over before you got the Kerdi smooshed into it. Smaller sections, work faster, mix thinset like a McDonalds Milkshake and you should be all right.

Jim wood
02-19-2010, 07:33 PM
I sometimes use a damp sponge on drywall and Hardi, it both cleans off any dust and puts a little moisture in the wall.

02-19-2010, 07:44 PM
Jim - Exactly right, you should always use a damp sponge on your substrate just prior to installing Kerdi. This is often overlooked but is a must do!

02-19-2010, 09:44 PM
Here's a video demonstrating how to apply Kerdi. The application part starts about 2 minutes in. The thinset looks quite loose to me.

02-19-2010, 11:46 PM
Second what has been said. Mix it looser, wet down the drywall first, and apply more pressure when you work in the kerdi.

02-20-2010, 12:29 AM
Thanks guys will do. I figured somethinf wasn't right. Will use the sponge too to dampen the drywall and the kerdi.

02-20-2010, 12:41 AM
Thanks for the video link martin my thinset was maybe as thick as what he used on the floor deffinately have to mix it thiner next time.

The Kid
02-20-2010, 01:24 AM
And dont go pulling at it this time. once your done, leave it be. Itll be fine.:)

Brian in San Diego
02-20-2010, 09:45 AM

I might add this little tidbit. Once you have your thinset on the wall and the kerdi smoothed out and imbedded, peel that piece of kerdi away from the wall and check the coverage. You want thinset to completely cover the wall and the kerdi...if it isn't then you need to make and adjustment to your process. If you do have 100% coverage then put the kerdi back and smooth it back out and press on. You now know what it takes to get the coverage necessary.

Then do like Jeremy says...leave it alone.


Houston Remodeler
02-20-2010, 10:49 AM
You will know you have 100% coverage by looking "through" the kerdi too. From your pic you can see the lines from the notched trowel through the kerdi. That means its not embedded well enough. When you are applying kerdi, press until those lines go away. Its easier to see those lines, or lack of them, with grey thinset.

Houston Remodeler
02-20-2010, 10:55 AM
better pic.

02-20-2010, 06:02 PM
Ok I think I will get it this time. I didn't try to pull it off at first it was I seen it wasn't sticking near the edges so thats when I tried touching the edges and when they seemed like they wernt sticking i lifted with my finger nail and it came up way too easy for my liking I knew something was wrong. Thanks again for the pics Paul. And thanks to everyone else for the quick responses I really appreciate the help.

02-21-2010, 09:25 AM
Do you think it's ok to thinset over the old thinset or should I scrape it off down to the drywall? The kerdi came right off with no problems just wondering if I need to scrape the old thinset off because it's not coming off to easy.

Brian in San Diego
02-21-2010, 09:28 AM
The old thinset isn't going to give you a very smooth surface and that could prove to be problematic for you. Try rubbing the old thinset with a brick (yes, a regular old brick) and see if that doesn't help smooth it out. You want a smooth surface to start. If there is thinset left but it's all smooth make sure you sponge it down with a damp sponge before applying the new thinset.

John Bridge
02-21-2010, 09:28 AM
Hi Jody, :)

If there are any ridges or bumps, they should be scraped down. Then make sure the surface is not dusty by wiping over with a damp sponge. Make sure you keep your new thin set "loose," not runny but loose. Don't try to spread too much at once. :)

Houston Remodeler
02-21-2010, 09:34 AM
You can get one of these to "sand down" the old thinset. Much more ergonomic than rubbing some old brick by hand. Home depot, $11.87 in the masonry section

02-21-2010, 09:37 AM
Thanks John,

There are ridges from the trowel if I flat trowel them in would it be ok or am I going to just dig them out when I go back over with the notched side?

Houston Remodeler
02-21-2010, 09:44 AM

The goal is to get the wall as smooth as possible to work on. That said, you don't have to remove every atom of thinset from the drywall. You will find that you can "even out" the surface by using a rubbing stone over it. There can be little hills and valleys from the old thinset left behind. You will know you have it right by rubbing your hands over the surface. Compare the after to the before. You'll feel the difference. When you re-thinset the walls, dampen the wall slightly with a damp sponge. The old thinset will suck the water out of the new thinset faster than you can put the kerdi up. Use the flat side of the trowel to skin coat the wall to make sure you have all those little valleys filled in. Then procede to apply thinset as normal.

John Bridge
02-21-2010, 09:48 AM
But . . .

Be very careful with the rubbing stone or with any scraper that you don't wear through to the Kerdi. The membrane won't stand for a lot of rubbing. ;)

02-21-2010, 09:51 AM
Paul thanks I have it coming off pretty easy now. I may spray it down with a water bottle not soak it but mist it.

Houston Remodeler
02-21-2010, 09:55 AM
oooohhhh I thawt HE meant taking the thinset off the drywall.... ooops

John Bridge
02-21-2010, 10:01 AM
Yeah, she does. I'm just having one of those, ah, uh, er, senior moments. Sorry. :D

02-21-2010, 10:08 AM
Yea, what John meant was don't rub down so far that you take the paper facing on the drywall down to the gypsum core. :D

02-21-2010, 10:48 AM
Haha sorry guys she's really a he!

03-02-2010, 06:53 AM
Ok guys another question. I put the shower tray in yesterday and noticed when I walked on it that it left some shoe marks from when walked on it to make sure coverage was good. I have been going back and forth weather I am going to put down 1 inch mosaic or 2 inch mosaic on the shower floor. What would be better in your opinion? I seached schluter and dont see a recomendation for tile size or minimum tile size for floor. I am worried about the tray making these marks in it and will it hold up to repeated walking on it after it is installed with 1 inch mosaics. Also what about after I get kerdi down on it. Just the kerdi can you walk on it or will the thin layer of thinset break up? I'm about a 270 pound guy and kinda worried about this tray holding upor will the thinset kerdi then another layer of thinset and tile make the difference and strenthen this tray? Has anyone had any problemsin the past with grout cracking or depressions made with these trays?

03-02-2010, 07:07 AM
Hi Jody,

I know Ditra has a minimum 2" tile size but not sure about the foam tray. I think the 1" mosaic would be fine. One of my trips to Schluter training in SC there was a bit of a torture test on the foam tray. I believe it was 1" glass mosaic tiles thinset to a foam tray (with Kerdi over it). After 2 days both a car and a forklift were driven over it without a problem.

Now if you were wearing stilettos in the shower then maybe the point load on an individual tile would be a problem. Don't think you'll be doing that though. :D

The foam tray without Kerdi and tile installed is susceptible to damage so you want to cover the tray with a scrap of plywood until you are ready to install the Kerdi and tile. :tup2:

03-02-2010, 07:22 AM
Now if you were wearing stilettos in the shower then maybe the point load on an individual tile would be a problem. Don't think you'll be doing that though.

Now Joe maybe I won't be wearing the stilettos but you never know what might follow me home to take a shower!!!

I seen the picture of the forklift on the curbless ramp. I guess the strength is in the products all combined together but was just a little scared with the 1 inch tiles when I seen the foot prints after I put the tray down. Worst case guess I would have to pull it up if it did smash down.

03-08-2010, 09:05 AM
Couple of quick questions on what the suggested method is to install the tile where floor tile meets wall tile.

1. Going from the main bathroom floor to the curb. The tile I'm installing has a factory edge that is kinda beveled I ended up with a full tile that meets right up to the curb and the factory edge will be hidden with the thickness of the thinset and the tile on the vert edge of the curb. Should I install the factory edge down towards the edge of the floor or should I install it towards the top of the curb? The top of the curb will have bullnose edge on both sidesof the top.

2. I am installing the 1x1 mosaics on the floor in the shower. Should I use grout or caulk around the base in the shower what is prefered? Or the correct way of doing things?

Brian in San Diego
03-08-2010, 10:25 AM
1. Dealer's choice but I would say put the factory edge up at the curb. Hopefully the edge at the floor will be hidden with caulk or grout.

2. Industry standard is to caulk all changes of plane. There are some who violate this standard and grout those joints. Like me..:D

04-22-2010, 07:02 AM
Question about split face travertine. I was going to use split face travertine as an accent border in a shower it is going to be at the top of the shower so it wouldn't really get wet but would be in wet area. I know I have read it wasn't recomended for a wet area but if I seal it would it be advisable to use this? in the shower? Also if I decide to us it in the niche would that be advisable or no? I would also seal it there.

Brian in San Diego
04-22-2010, 07:16 AM

Where did you read it wasn't for a wet area? I'm wondering why a natural stone couldn't be used in a wet area. It came out of the ground and probably has seen it's share of water in it's million years of existence. Many will not use stone in a shower due to the maintenance concerns of keeping the stone looking good after being subjected to body oils and residues from soaps, shampoos and conditioners.

I see no reason why you can't use the stone in the shower especially if it's above the shower head. I think the maintenance concerns would be greatly reduced.

I merged this thread with you original shower thread. Please continue to use it for all your project questions.


04-22-2010, 07:37 AM
Thanks Brian it said on the daltile website not recomended for wet area. I know people use travertine in wet areas but i thought maybe it was something different about the split face or something. So then I should be ok to use it as the back wall of the niche then correct? Because that is where it would probably be subject to the most water. Now other thing I don't think I metioned is this is mosaic split face its 5/8 x 1 inch pieces on 12 x 12 sheets

04-22-2010, 07:52 AM
Most folks don't grout that kind of mosaic. Lots of crannies on the surface of the split faces, and lots of grout lines. I think that may be why Dal-Tile doesn't recommend them for wet areas.

04-26-2010, 07:12 AM

I was thinking about a change of plans with the split face I have two pics attached in the first one is a pic of the shower the shower head and controls will be on the left wall in the pic what I wanted to do was put the split face on the inside of the niche that is the back wall in the pic and then on that knee wall that faces the wall where the controls and shower head will be. Do you think that it will be a problem if I put the split face in these two areas if I seal them? not sure how wet both spots would get but they are in a wet area. I know if you seal the travertine it should be ok in wet area, but as Bob stated about grouting im not going to grout these two spots. The thing that has me asking is the travertine split face is really tight together but when i hold up the back of it I can see light shining through. and wondered if the sealer doesnt seal it completely if it will be a problem with the water getting to the thinset?

04-26-2010, 10:39 AM
Also does anyone know a matching caulk for custom's linen grout?

04-26-2010, 11:17 AM
For what its worth I used it about chest height in a shower,and yes you can see light through it.So water will pass through it.your niche will have kerdi or a waterproof barrier behind it,however if the moisture that accumulates in the crevices left in travertine has no place to go and puddles or builds up in btm. of niche that might be a problem.I sealed all mine with 2 coats of the best stone sealer I could find it was a reactive silicone polymer that gave it a slight wet thing though whatever sealer you use follow the directions to a TEE!!If not you could get a yellowing or buildup of sealer that detracts from the look of travertine instead of enhancing.The good news if you should appy to much or let sealer sit to long before wiping excess off.You can actually dampen a rag with the product and wipe the spots where you overdid it.(the solvent in the sealer will dissolve excess left by mistake)PS if you do decide to grout the small spaces it can be done,just takes time and effort slightly wetter grout.hope this might help,ps water goes through grout also,so dont ever just depend on the grout to seal out water,The grout helps shed off the majority of water but the water protective barrier should funtion even if none of the tile in shower is grouted,thats why kerdi type drains have weep holes to let moisture that has seeped through grout have a way out.JMHO

04-26-2010, 11:27 AM
What was the name of the sealer that you used or what is the best everyone recomends if i go this route? The shelf in the niche will be sloped but im sure that there could be the possibility that water could get in the corners. Not sure if I want to take on the task of grouting this man i dont even know where i would start with doing that. That would be really pain full I'm thinking.

Brian in San Diego
04-26-2010, 07:56 PM

I am partial to StoneTech pro series...Enhancer Pro and Impregantor Pro. Enhancer really brings out the color of travertine. Makes colors come out that you wouldn't even know were there. If you want to bring out the color and slightly darken then use the Enhancer Pro. If you just want to seal use the Impregnator or you can use a combination of the two. Make sure if you want to Enhance you do that first. It's critical. Once sealed it cannot be enhanced.