I am at odds here locally.
Seems two plumbers I contacted have informed me that the slope on my large shower is to be made atop the pan liner.
I believe I have read on here that the slope is done first and then the liner installed.
Am I mistaken?
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Replies
For Kerdi membrane, you are correct. Whether they are floating a mud-bed or using a pre-sloped shower pan, the Kerdi goes on top.
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with a pvc liner they are correct.
Preslope under it though so when water leaks through the mud base, the liner is sloped to the drains weep hoes to direct it out.
Some of us here have taken to installing Kerdi over a mud job.
Look up Schluters sytem for shower bases. No mud needed.
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If I read you correctly they are talking about a mud pan with a liner underneath. The liner, whether PVC, CPE or something else, is tied into the drain, and the drain design incorporates weep holes. For this to system to work correctly, there should be "pre-slope" under the pan material to make sure water will flow to the weep holes. The shower pan liner then receives a layer of mud >1 1/2" , the surface of which is also pitched to the upper portion of the drain.
I have heard people who favor copper pans to argue that the pre-slope is not needed, but this is because making the required slope out of copper is to hard, requires to much time/skill/cost. To me this is one of the main reasons not to use a copper pan.
Also, if you are using a fabric pan, like PVC, plumbers do not seem to be able/willing/bothered or simply lack the know-how to form the pre-slope.Therefore they say it isn't needed or they never do it that way etc. What other part of a plumbing drain system is not sloped? That is why I say that the best person to install the pan is the tile mason.
This is the way.
Build a slope to the drain about 1/4" in 12" approx. Install the lowest part of the drain ensuring it is the lowest item and at the low point of the slope.
Over this install the pan liner and seal under the liner to the drain.
Install the clamping plate dry over the pan liner. This has weep slots for any water getting past the tile.
Now you can install a "wet bed" over the pan for your finish tile. A few stones or pebbles around the drain is suggested.
More details on page 33-34 of the tile council of America 41st edition.
Without the pre-slope you invite water being trapped and minerals being pushed up through the tile joints.
Oh, and if you are working under the IRC codes, the IRC REQUIRES pre-sloping of the floor prior to the vinyl, copper, Kerdi or whatever barrier system you are using.
I dont know the other codes, but I am betting they require it as well.
If the tile institute tells you to do it that way and the code tells you to do it that way, I would not advise listening to 2 local plumbers. They are not the ones ripping up the floor 2 years from now.
What I've seen done has been mentioned: slight slope, then plastic liner tied to drain, then sloped mud tile base.
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I just had mine done late last year on a totally custom shower. I found out that the liner OK under the mud bed, but that it is best to have the liner over the mud pan. Reason being that the mositure will have to travel through the mud in order to be caught by the liner, thereofre the mud is always damp. Some people say that over time this will lead to a mold/musty odor. If you set the liner on top of the bed, the bed then stays dry as the mositure is caught prior to the mud bed.... Wish I had done it this way... We have pebble in the floor, so we keep a foam squeegy and sweep the floor after showering, this will helps keep the moisture to a min. Plus we are able to hit the glass as well. I think next time I will use Kerdi or schluter pan setup, seems foold proof and fast!
What say ye?
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Check your local building codes and it they allow the Kerdi preformed pan thats THE route to go!!! In my neck of the woods for some reason it won't pass inspection and neither will a mud base with Kerdi over it unless there's a preslope first.
I totally agree about not listening to your plumbers b/c the don't know tile work...most of em' anyway. My plumber who happens to be a great plumber falls short when he tells me I don't need a preslope under the lead pan he installs....yep...you heard it right...apparently in my neck of the woods a lead pan is still code which makes no sense to me what so ever but it is what it is.
You do have the choice of sloping the wood subfloor and not using mud as the preslope but IMO a mud preslope is easier depending on how big the shower is. I've done it both ways. On large showers a wood subfloor slope IMO is easier.
If there's any way you can go with a Kerdi presloped pan go for it. It's a lifesaver!! and contrary to some beliefs you can cut the pan to fit if it's equal on opposite sides although you can't cut off "that" much. You'd just need to adjust your first course of tile which is no biggie. I start my first course in that case a course or two higher then the pan then fill in below. I run a ledger board around the walls above the pan to set my first course of tile using shims (blocks of wood) to raise it to the level I need it rather then sinking screws into the wall...especially if the walls have been Kerdified.
Kerdi preformed pans are THE way to go...saves you oddles of money and it's a pleasure to work with...and a real time/headache saver.
The last job I did I had to use a lead pan...then i did my drypack under and over it and believe it or not I "Still" covered the the drypack with kerdi but not the walls being the customer wouldn't spring for it and it came out of my pocket...and I don't care what anyone says about doing only the base with Kerdi (and about 4" up the walls). I still think it's a million times better then not doing it at all. I actually have to say that those people that think I was nuts for doing it that way should re-evealuate what they're talking about and I'll debate them any day of any week about it b/c I've done it more then once (out of necessity). Anddddddddddd if you really wanna get psychdodelic about it you can paint Redgard on the walls over your Hardi (CBU) just overlapping the 4" Kerdi edge. Two coats is preferable if you go that route but one is better'n nothing....and nothing...well...people used nothing but CBU's for years with no Kerdi or Redgard and for that matter they've used MR drywall and it's held up forever if you keep it sealed. I don't recomend doing it that way but I'm just saying...and to make some people even more pizzzed off at me...I've see tile in showers over MR drywall installed with mastic and it's worked well for years and years. Ain't my personal style...just sayin'. Just trying to put things into perspective.
I find now a daze we do a lot of over kill but for this carp I'm no different usually. I always feel its better to be safe then sorry.
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