Kerdi Shower Liner

[r.coward]

I have been working on a bathroom / shower tile job. For the shower I decided to use the kerdi system because I have always thought it seemed like a good and sound way to keep water INSIDE the shower. However I did not anticipate the difficulty I would encounter installing the membrane. More specifically, my problem has been with air pockets under the membrane. ALSO, I am now concerned that the fabric may not be bonding adequately with the thinset (Kerobond) which I used. The air pocket problem was more of an issue with the shower pan than it was on the walls, but in both cases it was a "PITA". I had to use an 8" roller to work the pockets out, and with less than 100% success.

Has anyone had similar problems with this product? Is it just me? Any ideas on what I might be doing wrong?

I am thinking next job I will go back to my tried and true method of using troweled on vinyl coating for water proofing. I do like their drain system though.

[HS345]

Hello,
There is definitely a bit of a learning curve with Kerdi.

I use a combination of drywall knives, and a steel concrete float to smooth the membrane out.

What size notched trowel did you use?

Have you watched any of the Kerdi installation videos? The DVD should have come with your drain. Here is one I found on YouTube. http://www.youtube.com/watch?v=tmSznnc2yss

[ceramictec]

you just need to keep the sheet flat and smooth (with a flat trowel) the thinset out.
you could be using to deep a notch trowel.

also it is hard to get the sheet flat on the pan due to the concave of the pan.
but again, keeping it flat, troweling it out it one smooth left to right downward motion works for me.

[JTG]

Yep
Like a lot of things the first couple times dont' just flow.
Was you mortar good and loose? I found that really helped and the tools the other mention to get the air out. I really liked to use a 12' drywall knife.
JTG

[cx]

Welcome, r.coward. Please put a first name in a permanent signature line for us to use (UserCP/Edit Signature).

I would suggest you go to the Schluter website and view the installation videos they have available there. You might see something in those that would give yoiu a hint what your problem might be. I would also strongly suggest you buy and download John Bridge's Kerdi eBook. Best ten-dollar Kerdi tool on the market.

I can't see a roller being helpful at all with Kerdi. My weapons of choice are sheetrock knives. I like a 12" knife for the large open areas and find that pushing the blade forward across the wall rather than dragging it will help to get the majority of thinset flattened and moved out.

For the smaller areas I like a 6" knife. And for any places with small tabs or in any corners I want a knife in each hand, one to stick firmly (very firmly) into the corner while I drag the piece flat with the other. In smaller areas I frequently also use a 4" knife.

One of the most helpful tools I've found, though, is the Schluter-commissioned 1/8th" square notched trowel for applying the thinset. It leaves exactly the correct amount of pookey on the walls to provide full coverage of the membrane while minimizing the squeeze-out. That and getting your thinset to the correct consistency will almost guarantee you'll have no air bubbles and not much mess at the edge of the sheet.

My opinion; worth price charged.

[ceramictec]

Schluter-commissioned 1/8th" square notched trowel for applying the thinset. It leaves exactly the correct amount of pookey on the walls to provide full coverage of the membrane while minimizing the squeeze-out.

[cx]

Thanks, Brian.

That 11/64ths square notch there is moderately wonderful for setting those bigger mosaics where a 1/4" is just way too much and your vee-notch ain't gettin' it.

Prolly good for the designed purpose of installing Ditra, too, I would think, but I haven't tried that.

[r.coward]

I am the one who originally posted this thread. My name is Richard Coward, I am a contractor in Bellingham, Wash. Thanks to all who responded to my query about kerdi shower membrane. The trowel I used was a 1/4 x 3/16 V. I DID view the dvd which came with my drain. All I can say is it looked much easier in the video than it was in real life. I usually dont deviate too much from manufacturers instructions when I am trying something new, but in this case my GC felt that having a seam held together by thinset was not reliable so he wanted me to turn up the membrane corners in the pan 2" up the wall so that there wouldnt be a seam on the pan floor. I could see his point. Why have a seam in such a crucial area if you dont need one? The only problem was it did make things a little difficult turning that corner and still keeping the membrane fit tight to the corner and then up the wall. And I think it also made it more difficult to get the air pockets worked out. When I would get the air worked out to the edge, it had nowhere to go since the fabric turned the corner and went up at that point. For the end corners I did use the "pre formed" corners which came in the box.

What are the opinions here about this method? Should I have strictly followed the instructions? How reliable is a thinsetted seam? How do you guys do it?

Another question: Is there a chance of the fabric separating from the wall? I had to remove the shower pan material the first time and do it over because as I said there were air pockets. I was surprised at how easliy it came off.

And one more (last) question: What do you think is the relative merit of using the schluter system for wall and pan protection as opposed to using the troweled on latex material (I have used Mapelastic HPG)? If possible, please be specific.

Thanks again. I do appreciate the information. For me every day is like going to school.

[JTG]

Welcome Richard
Yes it is hard to get your mind around the Schluter method at first but it does work and work well. They have a cardboard box that it Kerdi lined at the CTEF school and it is filled with ice and water all the time. Has been for years now and like new. If you get the overlap required you have a water tight seam. Putting the Kerdi in like you were asked to do would make it real hard to get it installed. I understand why you had to fight it.
Yes it does seem like to comes of the wall easy. Not to worry. Get it up there with out air pockets and it will be fine.
As you mentioned there are a number of different ways to "skin the cat" as far as waterproof membrane goes. I like the Kerdi system because of the use of mortar. I'm comfortable with mortar. Doing another type of product is just something else you have to have in stock. Prior to Kerdi we used the Laticrete 9235 system and liked it but not having to paint on the goop a couple coates I don't miss.
I have never been able to get my mind around the paint on membranes that go on top of the mortar bed. I couldn't sleep at night with worry about what was going to happen and the change of planes. Don't have the worry with Kerdi.
Keep watching the forum and look for our summer event here in Seattle when John Bridge is in town. Been doing it for a number of years. Worth the drive down to throw back a few beers with the gang.
Hope to see you then.
JTG

[cx]

Welcome, Richard. Again, please go to the UserCP, find Edit Signature and enter the first name there. Some of the older members have trouble remembering a few thousand first names, eh?

but in this case my GC felt that having a seam held together by thinset was not reliable so he wanted me to turn up the membrane corners in the pan 2" up the wall so that there wouldnt be a seam on the pan floor. I could see his point. Why have a seam in such a crucial area if you dont need one?

Any correct method of installing the Kerdi on the floor will not result in a seam at the wall/floor junction. The "seam" will always be at least two inches from that junction.

I, too, tried turning the floor piece up the walls for my overlap there, but only once. Big PITA, that. I now use Kerdi Band and the pre-formed inside corners all around the floor/wall junction and then cut my floor piece to closely fit the floor only. I always have my wall Kerdi already installed (and usually tiled) before I ever get to the floor, so it all works our well for me.

And unless its really convenient to fold a sheet around a corner, I generally use the Kerdi Band in the vertical corners as well, and cut the wall pieces to fit closely to the adjacent wall.

It's a little more expensive that way, perhaps (Kerdi Band being more costly than the Kerdi sheets), but I find it makes life much easier when working alone.

My opinion; worth price charged.