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Old 02-17-2002, 05:26 PM   #1
John Bridge
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In another thread Tyler_M asks one valid question: "Why would anyone want to build a shower floor that leaked?"

The answer is that none of us wants to, but we've never had any practicle way to do otherwise, everyone but Tyler, that is.

There have been some "sort of" processes that have come out to keep water out of the bed. One of them is the Laticrete process, but Laticrete doesn't have a drain assembly, so they have to rely on the traditional clamping drain. This entails dipping the top membrane down before it reaches the drain area, and then installing a little mud patch above it all around the drain. It's difficult to understand what holds this little separate mud ring around the drain.

The other question I've had about the Laticrete process is that if it works, why is it necessary to install a traditional shower pan under it (as Laticrete recommends)? Conversely, if you're going to have a pan under the mud, why would you want one above the mud, too? If water does get into the area between the two, you're going to have a cesspool situation on your hands similar to what occurs when the pan is not pre-sloped and "swimming pools" exist under the mortar.

For a number of years the Australians have been building showers with the waterproofing on top of the mud, but the Aussies play it close to the chest when it comes to giving out information about how they do it. Australian tile standards, for example, seem to be very close to top secret. Furthermore, the Aussies have taken to building showers that aren't expected to last very long. Particle board is used extensively down under and is an approved substrate for tile. The so-called "hob-less" or curbless shower has become popular in Oz. It has not had time to withstand the test of time, though.

And that brings me to the Kerdi shower, which seems to provide a partial answer to the problem of keeping water out of the bed. I say partial, because the Kerdi system has not been adapted to mud floated showers like the ones I build. The Kerdi shower, in fact, is built entirely out of sheetrock. Backerboard could be substituted for the sheetrock.

I'm convinced that the Kerdi shower system is viable for medium priced housing where much of the work is presently being done over nothing more than greenboard. It also presents an alternative when backer board showers are the choice, although it will probably add so much additional cost to the equation that it will be rejected by home builders.

I'll always have to mud float the showers I build if for no other reason than to get the walls as close to perfection as possible. I would like to be able to incorporate the Kerdi floor into a mud application, and I think it can be done. I'm not quite ready to try it, though, until I work out a few minor details.

I would like to have your thoughts on the Kerdi shower and on the general subject of keeping water above the mud layer in shower floors in general.

[Anyone not familiar with the Kerdi Shower can check it out on the Schluter site:] http://www.schluter.com/english/prod...erdi-drain.htm

[Edited by John Bridge on 02-17-2002 at 06:35 PM]
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Old 02-17-2002, 05:41 PM   #2
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John

I have applied the Kerdi mat over a 30 yr. old mud wall shower.It was the best of both worlds;perfectly flat walls AND waterproofing.I have decided to build mud walls in almost every shower now and,of course will be adhering Kerdi to that.

The only way to keep consumers from looking at acrylic and fibreglass shower wall products is to impress them with building superior tiled showers using updated and superior methods and materials.
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Old 02-17-2002, 06:04 PM   #3
John Bridge
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Ron,

I want to use the Kerdi floor and drain, but I don't want to have to run the Kerdi all the way up to the shower arm, which is what you have to do if the pan is going to be on the outside of the walls.

What I'm envisioning is running the sheetrock down to the floor and doing the Kerdi installation exactly as they demonstrate it on the site. But I would only run the Kerdi up the walls about a foot and then continue on with poly. Now I could wire up the walls and float mortar as I usually do, treating the Kerdi floor like a conventional liner as far as the wall floor juncture is concerned, i.e. not placing any fasteners in the area below the curb.

One of my problems, though, is how to keep the Kerdi mat in good shape while I'm working on the walls with mortar -- how to protect it.

The other problem I have is that I don't like the sheetrock curb. I think it needs to be mud.
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Old 02-17-2002, 06:06 PM   #4
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I started using the Kerdi system at the end of 2000. When I built my first one I was not entirely pleased since I found the system hard to work with. I had air bubbles and dealing with the overlap caused some consternation , especially when using mosaics. I did watch that first application over the last year just to satisfy myself that it would not leak.

Having said that, I went back and looked at my records for last year and I totaled 9 Kerdi showers. All were done with backerboard walls. I have since learned to work with it and would not try to construct a shower any way else. I think it is a great system.

Ron's right. I have had many customers ask me if it would be better to put a cultured marble or acylic pan and then tile the walls in their shower, since they had heard horror stories about shower pan leakage. When you show them this system, it sells itself. Besides, nothing looks worse in a shower stall than to have the pan so different. I also want to show them that the tile industry is addressing the problems they encounter.

My 2 cents worth. Thanks.
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Old 02-17-2002, 06:17 PM   #5
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I prefer not to use sheet rock under the Kerdi.I think that Schluter is trying to prove that their membrane is so easy to use that sheetrock is acceptable under it.If I get to prep the shower walls,I install backerboard.Recently I've decided to build mud walls like you in all the showers,mostly for the reason that the wall is flat and plumb for the tiles.And I like to play in the mud.

I would then adhere the Kerdi membrane on top of the mud wall at 39" high which is the width of a roll of Kerdi.Have done over 15 showers already with their membrane.

I have a small job coming up in a $800,000 house.The tub surround and shower are clad in new green sheetrock already.And,wouldn't you know it,the pan liner is laid flat on the subfloor with an improper drain.Schluter has the solution for this job.
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Old 02-17-2002, 07:04 PM   #6
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John,

I took a look at the Kerdi system. Aside from the sheetrock substrate it looks like a good design. I think the closer to the tile you can keep the water , the better. I would think the Kerdi floor system would breathe better than a floor in which the moisture is allowed to go deeper into the mud.

Since the Kerdi design is nothing more than a membrane beneath the tile, what would be the disadvantage of using a roll-on water proofing membrane of the sloped floor ; then tiling over it?

Custom's brand of waterproofing membrane also claims to be an "anti-fracture" membrane ; which would allow for movement between the floors and walls. It would also make it easier to waterproof some of the irregular areas ; Dams, corners, angles, etc

Jason
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Old 02-18-2002, 10:39 PM   #7
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I too think this is a smart design. The only problem I forsee is the potential for the floor tile to loosen up faster if the floor joints split where wall meets the floor.

The system seems to be geared toward high stess locations (west coast) that is more prone to ground movement. If one were to make a silicone or urethane expansion jiont where the wall meets the floor as shown in picture 3006 at the

Laticrete site:
http://www.laticrete.com/archdtls/dt.../3000/3006.jpg

this would prevent a lot of excess water from entering under the tile floor. This sytem surely adresses keeping the water out of the cement. If by the current thinking that water/moisture absorbs in large quantities through the grout and into the thinset and then to the drain. Based on my observations the floor tile is bound to loosen up and crack prematurely. But, that's not my belief as you all have read and thats why I am a big fan of expansion joints as shown by Laticrete.

Tyler

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Old 02-18-2002, 11:11 PM   #8
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All I know is I had to remove some tiles I had thinset onto the Kerdi and it was EXTREMELY difficult to get them off.

John, I don't see any reason that the Kerdi could not be implemented with your mud walls. Could you explain what the details are that you need to work out?
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Old 02-18-2002, 11:14 PM   #9
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Tyler, Schluter makes a lot of expansion joint moldings as well. You might be interested in checking those out as well. http://www.schluter.com
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Old 02-18-2002, 11:23 PM   #10
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stullis,

Thanks, since I'm a fan of expansion jionts, I shall check them out.

Tyler
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Old 02-18-2002, 11:28 PM   #11
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Does anybody make an expasion joint that can be used for a shower area, specifically for the wall foor joint?
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Old 02-19-2002, 05:02 PM   #12
John Bridge
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Yep, Schluter makes them in metal and plastic.

(Damn, I'm starting to sound like a Schluter rep.)

http://www.schluter.com

Jason,

Peter N. (Schluter National Tech Mgr.) puts it something like this: "I like to see the mat. I know there are no holes in it."

None of the roll-on products provide a drain, so you'd end up with the Schluter Drain anyway, and it comes with a piece of Kerdi for the shower floor.
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Old 02-20-2002, 04:42 AM   #13
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Just to clarify things a little, drywall is used in the demo as an extreme to demonstrate the properties of the Kerdi membrane. The membrane may be used over any appropriate substrate with good bonding abilities.
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Old 02-20-2002, 05:12 PM   #14
John Bridge
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Dave,

What do you think of my plan, though? I mean, putting the kerdi in on the floor and up the sheetrock to a point over the top of the curb, and then lathing and mudding the walls?
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Old 02-20-2002, 08:11 PM   #15
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Well, after refreshing my drink, with a wall membrane shiplap, the only issue I can think of would be the penetration of the Kerdi with nails or staples. If the hydrophobic properties of the fleece were adequate, Hmmmmmmm. Protection would be required of the floor till tile. I am not seeing a time advantage here, however, it does keep the water out of the base and curb, hmmmmmm. May be an advantage or wash if you have to do the pre-pitch otherwise. Less liabilty......Hmmmmmmmm. I would have to ponder at length but on the face value it sounds like it has potential. Of course, officially, bad idea to poke holes in the membrane and the reason none are recommended 8 inches from the floor line. But we are talking proprietary here. I got to have another drink.
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