The takeaways from this video should be: 1.) Full coverage of thinset under the tile is necessary when using sheet membrane in a shower pan to eliminate standing water, 2.) All sheet membrane systems are not meant to be submerged for long periods of time as this one was, and 3.) The thinset used to bond sheet membrane together makes a difference. Multimax lite from Laticrete is best that I have found to minimize wicking under the bands of sheet membrane. See that video here: kzfaq.info/get/bejne/b8-mirJ1yqq1op8.html

Props man just for posting that! Took some guts and I appreciate you honesty in all your videos. Keep killing it man you’re a inspiration to many.

Unreal transparency and excellent info for us DIY guys not knowing where to place our confidence. Best practices is all you can do and go with what gets you the best results. Rare than any pro actually tests and proofs their materials and skills. Truly a use of the scientific method. You certainly aren’t lacking, sir. Thanks so much!

Thanks for being honest and posting this video despite not getting the results you expected. It is an extremely stressful situation to be in and it takes a lot of courage to share this knowing your customers are watching too. I admire you for your honesty, integrity, and relying on facts as opposed to the sales pitch. The reality is that no waterproofing system is perfect and water does find its way through the membrane and slowly destroys what's underneath. The shower will outlast the manufacturer's warranty only because it is not constantly submerged in water.

I’m a diy. I used the Schluter membrane and Allset then I covered it with 2 coats of Hydroban. I’m hoping that will hold up. Thanks for sharing this video and for your honesty and integrity.

I admire your great courage for posting this. You really looked "bummed-out" which is understandable. Please make another video to explain if/when Schluter responds to this.

Issac, much respect to you for not trying to hide the test results. Speaks highly of your character. Thank you.

Isaac, you just proved what I have also suspected for years, and I have installed my share of Kerdi over the years. I never trusted the thin set as a waterproof adhesive between kerdi and would always overlap as if shingling a roof. I have one word, wedi !!!

you did great explaining wicking,...this is exactly how i did mine minus densheild ,we used kerdi board,and i used dilex eke,soft joints,...sure is important to dry out,and get 100% coverage, and maintain all pinholes etc,thanks for your efforts and video,good ventilation a must,helps dry out...

I really hope for a follow-up video. I'm in the middle of installing the exact system (minus the Ditra Heat). Too late to turn back and at this point the only thing to keep my anxiety from going out of control is to Hydroban the pan and up the wall a considerable amount. Perhaps the whole thing. I do appreciate your integrity by releasing these results. I just really hope for a follow-up with some words of encouragement. Respect

I admire your honesty and integrity Love your videos I have tiled for 25 years. Stil learning

I love these videos, it does confirm my thoughts on tiled showers. They will wear out with time. Nothing is forever.

Hey Isaac, life’s about timing. I’m at the point of waterproofing another shower in my house. I’ve been watching your videos for over a year. My first shower in my house was done with the 2 float method using the rubber liner. I did that about 7 years ago. Hadn’t yet come across your videos. My current bathroom shower stands with the Kerdi mat down and Mapei’s AquaDenfense painted over that and on my Hardiebacker . I just could not bring myself to put up the Kerdi mat on the walls and use the Kerdi band over the seams with thinset as the bonding agent. It always made me uncomfortable thinking that the thinset was going to seal the Kerdi band to the mat. I believe it was your previous tests that changed the language Kerdi uses, from waterproof to water management. This was because of the idea that thinset is not waterproof, and this video really illustrates that. I’ve moved forward and am using silicone to seal the edge of my Kerdi mat (coated with the Aquadefese) to the walls also coated with Aquadefense. I’ve taken strips of the Kerdi mat to make Kerdi bands and overlapped the mat on the floor by an inch and a half and siliconed it in place to the coated wall and the coated Kerdi on the pan floor. I’m going to put my next run of the Kerdi mat horizontally around all three walls overlapping the Kerdi band just mentioned and work my way up, overlapping the sections so they act as shingles do on your roof, and sealing those seams with silicone so water won’t find porous material to be wicked. Any water that would touch the mat coming down the wall will pass to the next mat on its way to the pan without touching a seam that has thinset and without having to climb over a seam but rather drop down to the next layer, like rain on a roof. I really feel that the only way to seal Kerdi together is by treating it with some type of waterproofing so the fibers that are on the Kerdi won’t wick water. I remember watching one of your videos where you used Kerdi’s silicone on Kerdi mat to make a funnel to test the seam. It dripped. The silicone wasn’t the problem it was the fibers that prevented the seal from being water tight. I’ve watched you completely paint Ardex over a Kerdi mat and I thought that was smart. The fibers are no longer a problem and you can silicone a Kerdi band and then treat it with the Ardex or Aquaguard. This whole thing has me nervous but I’m thankful for your dedication to your trade and your integrity to deliver the results you find. Personally I think you should continue to think this through and develop your own method/system and market it. Your the kind of guy that people could support because your interest is all about integrity!

Good for you to post this video regardless of outcome. This has been my assumption/suspicion for years. Which is why i have never jumped into a sealed unit product line. I think i will keep with CBU off of poured pan, and topical waterproofing still. Thanks for all your videos brother. They are always informative. 👍🏻🙏🏻

I love watching this video and seeing other videos where you have grown from it and worked to find the best water prevention products/techniques. Way to go at it. I spoke with an Ardex Technical Rep. Today, who tried to suggest that your videos are not realistic. I have watched many of your videos and find them to be unquestionable. Thank you again, sir for this work.

Always felt this system was shady, seriously you're the man and thank you for proving! Isaac you're very positive in whatever situation's in front of you. Sure you're the installer of this product and good to know now this product has failed you and your customer. If I had this product installed by your company and you told me how it is, I would rather want to truth as soon as possible, and decide how soon and prepare to replace it down the road, 5 years? 10 years? and would still choose you to be the installer.

9 minutes in and I'm convinced to stick with a pan liner! I was always wondering how a thin set was used to seal two pieces of kerdi together never made sense. You proved my point with this video!!

I greatly appreciate your enthusiasm and professionalism. It most definitely adds to the dignity of the trade. I would like to suggest another test, one that may be more realistic. After removing the standing water let the test pan set for several hours. To make it more interesting, use both systems and test simultaneously. I am of the opinion, a traditional pre-sloped mud shower pan under these same test circumstances would have standing water on the mud pan itself also. I theorize, the Curdi shower pan acts the same as a pre-sloped membrane and the thin set would act as the mud bed. You are just eliminating one redundant step, the mud bed. Not trying to be critical but just bringing up a different viewpoint. I’m kind of a novice in the industry, I’ve only been setting tile for 25 years and a general licensed contractor for 30+ years.

Thanks again for another insight to help me improve my skill in the trade. Don’t get yourself down, the fear is for things that have yet to come. I’m sending all the positivity and good vibes your way. I’d like to work with you one of these days if it’s a possibility, Berkeley is not to far off… Stay positive my friend, full love for you and the heart to post even the bad.

You are an honest person and I can't wait to see the flex seal shower I feel like it would do better

Something I always do, and I'm sure I'll get grief, is I will set and grout the shower floor all the way tight to the backer before installing the bottom row of wall tile. I feel the added benefit of having the floor tile sealed with grout completely will help prevent the water from getting under the edge of the shower floor perimeter if the sealant is compromised. I never heat shower floors and use small tiles so I really don't think expansion is that much of a problem. I've done many kerdi showers this way for years and haven't had any call back issues. I learned young to always think like a raindrop when trying to waterproof anything. It always seemed odd to leave a vacant gutter space all the way around a shower floor for water to accumulate.

Dude your awesome for having the guts to show this. I'm sure alot of installers were being blamed but it looks like the thinset is the problem by wicking the water in between the kerdi.

Really glad you did this, it answers the question what happens. I'm still a fan of hot mop. Sold pans if possible.

Issac, you're a man of great integrity. I have a lot of respect for what you just did. I've been watching your videos for a while and have really enjoyed them....you make tile very entertaining. I should also say I'm a waterproofing contractor (exterior not bathrooms) and really didn't trust the kerdi system as I saw it. I just did a shower waterproofing for my house and I did the old fashioned way with copper flashing and tar. I'm curious what came of this with Shluter. Thanks again for posting this. Very brave!

TileCoach you rock. Thank you so much for doing what you do. Respect...

Thank you for your honesty and your commitment to the truth - excellent video

Subscribed. Your a man of integrity. Good luck with all your past Kerdi installations.

been watching videos on WEDI / Schluter for weeks now - as I have a wood substructure in my (old) apartment building, my feeling is the safest option to put in a shower in place of the tub is to put in a shower tray and just waterproof the walls and the connection from the tray to the walls

Schluter system is designed around the premise that you will have a family using a shower averaging 30 minutes each per day. And that while it’s not used the water dries and evaporates off including what gets under the tile. This why they have restrictions on commercial applications. Your test over stressed the system. It isn’t designed to be flooded for a week like that. Id rather see you build a shower system and test it in a way that simulates a person showering in it. And see what your results are after a few months or a year of that test. And don’t have anxiety they technically warranty it’s for life. Always love the videos.

Issac, I would not be overly concerned. In actual use your shower won’t be underwater for days or weeks at a time. When you subject a product to situations beyond its limits the results like this shouldn’t be that shocking. I’ve always assumed there would be moisture wicking with the thin set being the bonding agent. But with 2 or 3 fifteen minute showers a day with no water standing I can’t imagine there being a real problem for years and years. Thanks for posting though, I enjoyed the video and can tell you really care! Not many do anymore. 😃

First of all thank you! Now I am looking at tiled shower systems same way as I look at any roof. Soffit and ridge vents prevent accumulation of moisture underneath the roofing substrate.

We have used topical water proofing in every shower area since 1997 and i still haven't seen or heard any of them failed. One thing is common though that our shower also has underfloor heating which means everything dries faster when floor is warm.

Makes me go for a fiberglass pan with mortar, strategically placed for support, especially on a slab. 20 years ago I installed a fiberglass tub on a slab, I had access under the tub and packed mortar in the area where the slab was. The fiberglass is supported reliably by mortar.

Can only speak for myself. Did a marble bathroom for my daughter. I took the kerdi 8" up the walls for the shower floor and folded in the corners. Tucked in behind the cement board. The walls have kerdi down to the shower floor. Used a 10" band in the corner between the wall and floor. Brought the kerdi out 3' past the shower. The covered every joint with 3 coats of Ardex 8+9. Tried to make sure there are no voids of thinset in the shower area. I am 65 years old and have remolded many bathrooms. The old ways always had water damage. Everthing eventually fails but hoping this marble bathroom last 50 to 75 years or more.

This is real science, with real applications in the field. Great video. I am curious what would happen if you did several different small mock-ups of various systems / strategies and ran the same test.

I still float mortar. There’s so many advantages to the mot mop and mortar bed. I did a marble shower a few years ago and the homeowner talked me into using schluder. The lady of the house didn’t like the color and veins on a few tiles and wanted them replaced. I gently removed the tile and thin set but some of the Kerdi membrane peeled of where the wall met the shower pan. I patched it as best I could but I still worry about it failing. Haven’t got a call back yet but I’ll stick to the old school method. Helps me sleep at night

As a imstaller who works with this system regularly I'd like a follow up video on what the schluter rep. Explanation is/more info etc

Thank you very much for the information. I'm a DIYer and about to install a Schluter shower system. I will Red Guard all my joins and seams.

Good info man. Water damage is a motha amigo. You should find a water damage company and ask if you can “ride along” on their water mitigation process. Just to see more first hand water damage. Even floated tile jobs get damage as well. Thanks for the information man!

I'm going to be redoing my bathroom and have been debating Kerdi vs vinyl lining/traditional mud bed. This sheds some light

I'm sitting in a schluter shower.. tearing it out right now because the linear drain failed. Thank you for this

I always use the grout in a caulk tube on all inside corners of my tile because of the cracking issue I’ve had happen one time. And ever since that I have used the grout caulking tubes and never had an issue again. Around any tub base where the tile meets the tub and all inside corners of the shower and along the top where the tile meets the ceiling.

Well done. It takes guts to post that video. Kudos sir. Love your work and your videos.

Issac - always enjoy your video's. Thanks for the "Edutainment". It wasn't clear how long the flood test was prior to deconstruction in this video. I strongly suspect real life Kerdi showers don't see nearly the same pooling and capillary action as long flood test do - mainly because 15 minutes of flooding while showering followed by several hours of drying won't cause much capillary wicking. Real world showers don't have a couple inches of standing water for several days/weeks. Water pooling under tile without 100% coverage - probably; capillary action soaking substrates below/behind Kerdi - doubtful. Your video does show thin set between membrane layers allows wicking - how far the wicking goes depends on how long the membranes are submerged.

If Isaac goes missing, we all know who’s behind it 👀😂

It would be a great video to have a demo done on one of the first Kerdi showers you did in 2012. Actual shower application for 9 years should prove out the systems capabilities in real, long term use. Thank you for sharing the video. How long was the flood test?

(Thanks for doing the installation TEST videos Issac!) When we replaced our leaking/mouldy shower, I sealed all the Schluter Kerdi joints with one of the (waterproofing) products. +And: the whole pan, curb and niche to help prevent any wicking through the thin set. We felt the extra time and cost was worth it! *Our* ‘tile guy’ thought we were ‘just’ overly concerned with our waterproofing. This ‘redone’ shower should remain waterproofed for the life of the house!?

Cultured marble pans all day. No way a mud pan is drying out completely either even with good weeps. The slope isn’t enough to counteract the surface tension. Don’t turn your shower pan into a bathtub either lol

I’ve always said there should be a product to stick kerdi with, like a hydroban sealant etc, but i have never liked lot of features of the membranes, it’s time for schulter to stop trying to rake in money and revise their system. I always overlap all my bands with hydroban, just for added piece of mind…. too many times I read ohhhhh the warranty etc but I tend to think 25 years experience outweighs lot of recommendations by manufacturers of you take pride in your work and try to deliver the absolutely best product to the customers. Great videoBTW!

Im about to remodel my bathroom and after watching this... i dont know if i want to use Kerdi anymore. Im probably going to go with RedGuard (thin multiple coats). Thanks for the great info!

I’m from Australia and I love watching youre vids. The USA does things so different. We mostly use a plastic shower base that is made to be tiled over these days. It contains the grate/ drain and is curb less. It butts up to James Hardie 19mm Secura Exterior Flooring which is a thick waterproof cement sheet product. For the walls we use another water proof cement sheet product called blue board which is 7.5mm thick and never rots.everything under the tiles is water resistant and completely submersible for decades and then we waterproof it to make sure it’s 100 percent. Not saying our way is better but it blows me away that you place foams and timber and plaster products in wet areas.

I always feel good about my work. Then I watch your videos and start getting paranoid

Hi! I'm nobody... I always use the flexible sealant at the corners, both for my backer and my tile itself. A few sealants I recommend include polyurethane-based caulks, like Quikrete concrete repair for floors. I've pulled out my own tile jobs from 10 years ago using that product that still exhibit like-new flexibility. For side walls, I've used the very high-quality (expensive) siliconized acrylic caulks, specifically the gray, and they seem to last OK (not as well as the polyurethane). For gaps, I strongly recommend you use a backer rod of the appropriate width, since caulks are more *flexible* than they are *compressible.* Backer rods will allow you to maintain both flexibility and compressibility in your joints. TCNA agrees. Backer boards usually require such gaps in their data sheets. So leaving the gaps with flexible, compressible joints follows the guidelines of both the manufacturers and the TCNA.

I really appreciate this video. Thanks Issac

That really blows, thanks man l appreciate you doing this I’m doing my own mock up so l can get a hold of my rep, so disappointing!!!

Thank you for this information, you're a brave man. God Bless you!

I completely agree. If water gets through that grout, it has to have a place to go. I am against sealed systems also. I like the traditional way of making the shower pan so water can drain if it gets through the grout.. Good vid. Thanks for the honesty.

Thank you for your honesty

Great video! I have to ask though, have you done a test where you demonstrate what a shower goes through with day to day use without the prolonged soaking?

The simple solution is 2 layers of Redgard over the Kerri seams @ 1” overlap each side is all that’s needed

Curious to see if the wedi system does this as well. Since they use caulk to seal joints as opposed to the fabric bands and thinset. Also wonder if their shower pans weep water any better that gets under the tile.

Isaac, thanks for posting this. I really appreciate what you do, and I'm sure everyone else would say the same. I do have some questions, though - do you recall which thin set was used? To be clear, I am not a tile pro by any means. I recently attended a schluter workshop and got the low-down on what their expectations are. They insist that installers use any one of their 3 thin sets (all-set is usually the go-to), get 95% coverage between substrates and kerdi, and of course using the right trowel size per application. I imagine this was all followed as instructed since you mentioned the sales manager was with you when this was being displayed. That being said, I would stick to their all-set, get as close to 100% coverage as possible, get 2.5" overlap on every corner, and be sure to get rid of all gaps that are made with directional troweling. I think you even explained in the comment you pinned that a good chunk of what let to this failure was lack of thin set coverage and extended duration of water submerging. In a normal setting, I don't think this would even be the natural environment a schluter shower pan would be experiencing, correct? Accounting for the grade to the drain and following schluter's installation manual to the tee. Would love to hear your thoughts :D thanks man!

Any follow-up information after talking to your rep after this? Have they made any changes? Does using ardex 8+9 over the overlap or hydronan liquid negate the capillary action of water getting through to the foam portion of the pan?

I started in 2012 as well but epoxy grouted the floor an curbs, in 2014 I started grouting the entire shower with epoxy grout, only ever did 3 kerdi complete kits all the rest are Ardex 8+9 or Aquadefence

Hang in there Issac Your passion for truth will shield you from the perils of deception. Sharing this video is heroic. Some food for thought, drill 1/32” weep holes in the proud edge of drain flange. And possibly the use of Epoxy grout.

Thanks for posting this. Ive probably watched 30 of your videos in the last 4 weeks. The entire time I was thinking there's no way I'd use thinset as the binding agent. Have you run any test with anything like redgard or any other water proof binding and the kerdi set up?? I want to do a wide drain where the entire 4' wide bathroom drains at the far wall. This is a great example of how it _should_ be installed, but not the way I had it envisioned. I came home from vacation and my toilet had exploded. Lucky for me I get to do the entire bathroom. I'm going to make sure the ENTIRE bathroom is waterproof.

You should build a shower pan with kirdy and use some other waterproof paint on top of it and test. Thanks for sharing all the information

Yikes! I'm a DIY'er and I'm right in the middle of installing a sealed shower floor with deck mud topped with Kerdi. I'm using Durock on the walls and applying a topical waterproofing to it. I also coated the banding between the floor and walls. I felt like I was overdoing it, but now I think I'll put a second coat on it before tiling. This is discouraging, to say the least...

Oh man, I’m not going to sleep tonight! I have been using Kerdi for well over a decade, now I’m going to have a nightmare of all my jobs failing like that😮. Haha , so far, no call backs😅. To be honest, I’ve returned to a weeping system for that very reason, I just demolished a bathroom for a full remodel and found mold between the thinset voids and the backside of tile. As you mention, it was clearly visible in the grout that there was sitting moisture there.

But in a weeping system the weep holes get clogged with efflorescence and we are back to square one.

Sooooo. What is the safest system to be using for a shower? I haven't had my shower done yet because I'm waiting for the right answer.

Thank You for your Honesty!

Very surprised...Thanks 👍

You need to slide the tiles back and forth perpendicular to the trowel lines to knock those ridges down you can get 100% coverage by doing that

..." this is going to be a fun video"... Im not sure if American building standards allow painted on waterproof membranes but i'd love to see a video of you using either Ardex hydrothane or Davco K10 and your thoughts on whether its easier to apply ( which I can tell you right now it is) and the integrity of the product(s) Another thought is perhaps making the grooves from the notched trowel extend right to the very edge of the drain so water can flow fully to the drain to help water not get trapped in voids I think fully immersed water like you had will give a different result to a "garden variety showerbase " where water would drain off better Great videos , im loving them, thanks

Is Keri approved for use in a swimming pool? Id like to see a more application accurate test, possibly run water over test for 15 min a day for a week and see if results are the same. My boss always made us use cement board for all wet locations theory being if there is a plumbing failure inside the wall it would save the tile. We all have theories I guess.

Thanks for your courage

Thanks brother,,,, you have courage,,,, I'm not installing it ever again

Thanks for posting this Issac. Bottom line is ( that we both found out ) the system is really not meant to be flooded. Only a liquid applied membrane is. That was a liquid is called for in pools.

I would retest it and back butter the tiles. I would think it would reduce those gaps significantly. Would be a good follow up video.

Not to dog on you but… I’m an electrician so I follow you for good advice for my own home projects and you’re good obviously or I wouldn’t have subscribed, point is you have recommended Sal DiBlisi and I’ve learned a lot watching his videos and the first thing that came to mind was I new he would say 100% coverage on any shower floor. Better start paying attention! Lol, good video 💪🏽

As an "intermediate DIYer" that's dreaming of remodeling our bathroom, and just starting to look at shower options... am I understanding correctly that this problem could be at least partly mitigated by using a sealant around where the wall and floor meet, vs just grout? Or is it kind of inevitable since grout isn't waterproof all over the bottom?

Awesome video! Can u try a hydroban system demo and see if the moisture creeps up the wall? Doesn't seem like kerdi is all that its cracked up to be😫

Hi Issac, i watched your videos about Kerdi membrane when i did my shower, also i used the Ardex 8+9 as you did in one of your videos(2 coats), do you think i will have the same problem?

Watched this video, I am glad to see someone as conscience as you. I enjoy all your videos. Regarding this video, water finds a way in and out, so either you change the way gravity works or you have to use the best available system, at the time. People have been dealing with these issues for centuries. Fungi have been around longer than the human race... If you do not want water damage of a shower , use a bath tub ! I do not see how any system will stop the issues you mentioned? You will always have seams and joints, coatings fail too. I think the most anyone can ask for is X number of years before replacement. The home owner assumes the risk of having a tile shower. The most they can expect is proper installation with current technology, to minimize that risk, not eliminate it. If you have a shower make sure you dry it out occasionally. Maybe floor pans are too water tight and you need to give the floor pan the ability to dry and not seal it off from the air. I mean if water gets behind/under your Red Guard then what ? Sounds like the same problems.

I have a question. Since there is a fabric between the actual membrane itself on the Kerdi system, doesn’t that act for the same purpose and reasons as wood the concrete floor? Because the thin set doesn’t stick to the membrane sticks to the fabric that small space between the fabric and the membrane would mean it can always weep water.

Thank you SIR !

I have a Kohler cast iron shower base. Would Kerdi board have this kind of problems when installed for walls?

Hi Issac, we're having issues with the drain the red adhesive is coming lose from the stainless steel drain so it leaks. I've always have rather use conventional shower liners, architect spec'ed Kerdy so we had to use it.

Wow. That failure is with a static only demonstration. Could you imagine if the flexing of the floor from the in and out traffic of the shower was taken into consideration

Every time I look around, someone on KZfaq is showing videos of these heavily marketed products failing. I have lived in my home for over 20 years. I have renovated pretty much everything but the shower, which came with the house. Mainly because it looks classic and functional and I haven’t had leaks or mold issues. The old school technology works and it is tried and true.

I’m now quite concerned (worried?). I’m a DIYer who did my large shower with Kerdi, carefully following the Schluter instructions. The shower had major rot and live termites from a very poor shower install by the home builder. After seeing this, I’m beginning to wish I had done a “belt and suspenders” and added a liquid membrane over the Kerdi seams/overlaps and/or maybe used CBU instead of regular wallboard.

Even with showers waterproofed with RG. I leave a small gap around the drain. So water goes to the weep holes. Spoke with my local Custom Rep on this. They say to waterproof up to the drain. Not so good with marble tiles. Especially white marble. The water never dries with daily use. The thickness of the tile and the drain edge always stayed wet fanning out 12in or so around the drain. So weep holes are a good idea. What are your thoughts on this?

Thank you, Issac! I’m. It trying to sound petty, but this is for those argued and laughed when, said before that, I would never trust thin set to waterproof. This video any many of your other test proves it! Imagine daily use of family of 4-5 or more over 10, 15, 20 years! I will always use topical membrane over thin set.

So we've seen you install Kerdi since this video, what are you doing differently since you have discovered this failure?

question! I self leveled the floors but… I know that there should not be no more than 1/16" level variation in 24" (for large tile.) I am installing uncoupling membrane then Porcelain 16 x 32 tile. Question is: putting the level behind the toilet flange there an 1/8 will there be noticeable lippage or with mortar and level clips I will be okay 🥺

do this same test with your laticrete hydroban material that you use and see if the same happens?

So when are we going back to old school way? or flex seal will save the day

I've always wondered how good that system works but what about if u have covered it with regard before instal

Revealing and brave. Could this still happen with a PVC pan liner with drypack and weeping drain?