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Unread 06-06-2012, 03:59 PM   #1
jillquack
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Long tile shower with linear drain

Hi there, friendly John Bridge Forum folks!

I've been lurking and reading a lot here the last few weeks as we've been prepping for a full bathroom remodel. We've got the whole room down to the studs and are doing some joist repair/reinforcement at the moment. Actually, I say "we", but my husband and his father are doing most of the work, and I do lots of research, planning and drawing. They both have experience with home building and repairs but none of us has built and tiled a shower. But I've learned so much already from the forum, so thank you all!

Our project: We're doing a full-tile shower with a linear drain. I haven't decided on the linear drain yet but am leaning towards the Laticrete drain using Hydroban to waterproof the whole shower. But I'm also considering doing a complete Kerdi shower or using QuickDrain with their waterproofing membrane on the floor and Hydroban for the walls.

The floors (in case you want to know): old 3/4" diagonal subfloor wood, on top of that will be 3/4" plywood. The joists will be, at the minimum, 16" apart on center. In some cases we've added additional joists for extra support where older joists were notched to hell and we couldn't sister them because of where the drains and vents need to go.

Here's a rough plan of the shower with some dimensions:

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It's a small Jack and Jill, but we're trying to have as spacious and luxurious a shower as we can. There will be no door, just a fixed glass panel sitting on the top of the curb.

We'll be building a shower pan with deck mud over roofing felt and wire mesh. The curb will be high enough to account for the 2" minimum depth required between the drain and threshold.

My questions (I have a ton of questions but I'll start slow):

1) We're building the shower pan with a slope spanning the full length of the room, 77 inches. The Laticrete linear drain installation manual says: "Bonded mortar beds over EGP shall be 3/4"(19 mm) minimum to 1 1/2"(38 mm) maximum." So starting with 3/4" of mud at the drain, and rising 1/4" per foot, that amounts to 2.35" depth of mud at the far wall.

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So the 2.35" exceeds the maximum bonded mortar bed depth specified by the Laticrete drain manual. I also seem to remember reading that anything over 2" would need to be reinforced. Would I need to switch to an unbonded mortar bed with wire mesh reinforcement? And if so that would increase my minimum depth to 1 1/4", correct?

I realized when I drew the picture that the slope would actually begin at the end of the drain, not from the wall. So that would actually knock off a few inches from the length of the slope, but probably not enough to make a difference with the max. depth problem I'm guessing.

2) We were originally planning a 36" wide shower which was the perfect size for a number of 36" long linear drains. Because we have limited space the final width of the shower floor is looking like it'll be more like 34". And there aren't any linear drains that width that I can find (I've seen 30", 32" or 36").

The Laticrete drain manual says the "typical" installation is from sill plate to sill plate, but it doesn't say it needs to be that way. Can we float the drain in the center of the shower floor, but still flush against the back wall?

And from what I've seen from other drains it looks like they typically have a 1" flange around the channel. Is the flange sloped or is it flat? Would this kind of installation be okay:

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Or is it preferable to have the the wall substrate (and eventually tile) sitting on top of the flange like this:

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Thanks in advance!
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Unread 06-06-2012, 05:52 PM   #2
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Welcome, Jill.

Looks like you've done some homework and that's certainly a good thing.

1. Keep in mind that the 1/4" per foot slope in a shower pan is the minimum requirement. If my slope was to be a tile surface six feet to the drain, I'd want more slope than that, but that's your choice.
Quote:
Originally Posted by Jill
"Bonded mortar beds over EGP shall be 3/4"(19 mm) minimum to 1 1/2"(38 mm) maximum."
I'm a little surprised to see that since there is no way to make a bonded mortar bed over EGP.

The minimum 3/4" thickness requirement would come from one of the TCNA published methods for tile over wood floors you may have bumped into (F145), which requires stapled down metal lath and the 3/4" minimum thickness, and the mesh and 1 1/4" thickness from a different floor method (F141). Neither method considers the slope required for your shower floor.

Shower floors get some special considerations in the ANSI standards and are presumed to be of uniform thickness (minimum 1 1/2"), have steel mesh suspended in the vertical center, and be installed over a pre-sloped waterproof membrane. The requirement for the mesh is currently under review for removal from the standard.

In your particular installation I would have no concern at all with packing my deck mud in that shower floor to whatever depth was required for a proper slope to drain. I would keep to the minimum of 3/4" at the thinnest section and let the other end be what it needs to be, which, for me, would be close to three inches.

I would, of course, start with a cleavage membrane (actually used in this application only to keep the plywood from sucking moisture out of your deck mud) and then 2.5lb metal lath well fastened to the subfloor. I'd want to keep my deck mud as dry as possible and I'd wanna cover it all with polyethylene sheeting and let it cure a few days before working over it.

2. Depends upon which linear drain you select and how it installs. Some are of a clamping variety, some have an integral membrane attached, some............I dunno all of'em.

There's been a lot of discussion since the became popular on just how to treat the areas at the ends of the drain if it's not actually wall to wall. Bottom line seems to be that you need to be a little creative there and be sure there is still a little slope to drain in those areas.

On your wall preference question, that, too, would be dependent upon the drain you choose and how it installs. If you actually hafta bond your waterproofing membrane to a portion of the drain, I'd want as much surface area for that as I could get.

There is also a tile industry requirement that your shower curb top be at least two inches above your shower floor. That's not code and you can ignore it without any legal concern (not so the 2" above the drain) if you want. Just pointing out that it's in there.

I know you didn't axe, but y'all could make that entry opening a little smaller if you want. And I would unless the shower will be used by very large persons.

My opinion; worth price charged.
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Unread 06-06-2012, 06:46 PM   #3
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Thank you, CX! That is a lot of useful, helpful information on my shower slope right there.

So you'd increase the slope, eh? Would you be worried water would get 'hung up' at the highest part of the slope and not drain all the way to the drain over such a long distance? Or is it just that you'd want the water to drain quicker? Or something else I'm not thinking of...

Thanks for the heads up on the height of the curb from the shower floor. I was wondering if there was a standard for that. A bit worried that a small step up would be a recipe for (tripping) disaster. So I'll try and work that in.

What size opening would you have on the shower? The 77" measurement does not include backerboard and tile, so the actual length of the finished shower would be more like 75 1/4". So that'd leave us with an opening between the wall the glass panel of 25 1/4". How much smaller would you make it? (We haven't ordered the glass yet so that can still change)

As for the linear drain, I do like the idea of having the membrane pre-attached to the drain (like Kerdi and QuickDrain have I think). It just seems like less possibility for error (leaks around the drain). However I'm a bit intimidated by a full-Kerdi shower, and also by the idea of mixing and matching topical waterproofing techniques (Kerdi drain membrane/Hydroban, or any fabric membrane on the floors with liquid on the walls). It seems like people do that quite often though, I just don't have the experience to convince myself that "yes, these two things will absolutely work together". I probably just need to take the plunge and decide which drain/system I'm using so I can get my questions answered more precisely

Thanks again!
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Unread 06-08-2012, 10:35 AM   #4
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Does anyone else have an opinion on the slope for such a long shower (77")? Will 2% be OK or should we go higher just to be sure everything drains properly? We're going to be using 1" hex tile on the shower floor if that makes a difference.

And also, taking another look at the Laticrete Linear Drain manual, I spotted this:

Quote:
In both bonded and unbonded mortar bed installations place enough LATICRETE 3701 Fortified Mortar Bed where the linear drain will be set to support the bottom and under the flanges of the drain trough. Minimum height from the flange to the substrate should be 1-1/2" (38 mm).
So that would mean with a 2% slope the high end of the deck mud would be over 3 inches deep. And with the increased slope CX recommended (closer to 3%) it would be 3 3/4" deep. With that height of deck mud would we still be safe using CX's method of using dry deck mud and letting it cure, covered, for a few days? Or would we need to change to another method with more reinforcement?
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Unread 06-08-2012, 11:18 AM   #5
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Instead of worrying about Laticrete's general recommendation for 1 1/2" under a liner drain, focus on the specific instructions for the actual brand that you are using, such as the Kerdi-Line drain at only 3/4" (If I remember right). You can watch some great videos on Youtube of it being installed.
Water can not tell how long your shower is, and will drain just the same in a 3' shower or a 300' shower, as long as the slope is still 2%. 1/4"/ft is a universally accepted standard and will work just fine. The only time I consider a steeper slope is if the tile for some reason has very rounded edges that will be hard to get the grout up flush to the top. With deeper grout ruts on the rare occasional job, I might want a little more fall to get the joints a little drier quicker.
The other time to consider steeper fall is for a beginner doing your first mud job with standard center drain. The rounded slope that varies all around the shower means that some areas are hard to get a straightedge to, and first-timer may risk having pooling areas where the slope isn't right. With a linear drain, however, the slope is all even and only in one direction. It is much easier to handle with straightedges and there really isn't the risk of flat spots or pools, even for your first try.
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Unread 06-08-2012, 12:08 PM   #6
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Thanks, Tom. It makes more sense to me that the slope wouldn't depend on how long the shower was, unless you were using something like those river rock pebbles that made the surface more 'bumpy' (the deeper grout lines between tile like you said). But I'd still like to hear CX's reasoning for increasing the slope, if he reads this

I think all the videos I've seen of the Kerdi Linear Drain installation use their pre-made shower pans. I haven't been able to track one down that shows installation over a mortar bed. If anyone knows of one I'd love to see it.

The only thing I can find that mentions mortar bed thickness for a Kerdi drain is for their regular (non-linear) one:

Quote:
When installing KERDI-DRAIN over wood substrates, the minimum thickness of mortar required at the perimeter of the bonding flange is 1".
I can't find anything mentioning minimum thickness in the Kerdi Line Drain installation instructions.

Still trying to decide on a drain/waterproofing system! I think it is between Kerdi and Laticrete now. QuickDrain's look like a pain to clean.
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Unread 06-08-2012, 04:44 PM   #7
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Sorry I can't remember the minimum there for sure. The last two we did had dropped-down floors and so had nice thick mud there at the drain. If you called Schluter I'm sure they could tell you quickly. You might also consider using their whole kit and get the foam base with the drain. Very quick and easy compared to mud. Perfectly straight slope and you can get the very minimum height that way.
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Unread 06-08-2012, 07:03 PM   #8
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Got an email out to Schluter asking about the minimum depth beneath the drain Will post the answer here when I get it.

I do like the idea of the pre-made trays, they just don't make 'em as long as our shower needs to be. Though it looks like you can just extend the slope using deck mud to the length you need, like they did in this video here. So I'll be considering that option, too (Because I wasn't already overwhelmed by the number of options before).
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Unread 06-08-2012, 09:04 PM   #9
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Yeah, extending the length is very easy, just follow the foam board with your straightedge to screed the mud off to the proper slope.
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Unread 06-08-2012, 09:10 PM   #10
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This will mean the perimeter will no longer be level. This may or may not bother you. Most Pro's like a level perimeter for cosmetic reasons, even if that means the slope changes, which most folks can't detect, as the slope normally changes anyway.

Clear as mud yet?
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Unread 06-09-2012, 12:58 AM   #11
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Paul: Totally get what you mean -- though in our case we're using a linear drain so the perimeter isn't all the same height anyway. I probably confused things a little by posting a link to a video where they extended the tray for a non-linear drain, but I was guessing the same thing could be done with the linear tray/drain. Slightly clear-er than mud
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Unread 06-09-2012, 07:28 AM   #12
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Jill,

as to your earlier question, I just did a large shower with a Schluter linear drain. I had a 48" drain and 72" wide wall that the drain set on. I just sloped those corners slightly towards the drain, and everything drained perfectly fine, and I used 13" tiles which are much less forgiving than hex tiles if everything isn't perfectly flat and on the same plane. With your hex tiles you won't have a problem at all.
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Unread 06-09-2012, 10:19 AM   #13
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Hi Jill,

I just read this thread through to get caught up on it.

As far as the slope of the mud floor, 1/4"/ft is the minimum and 1/2"/ft is the maximum slope. The minimum slope works fine, but it assumes there's no user error. When you do the mudwork, if it's not perfect, there could be parts of it that are 1/8" per foot or less. So do a 1/4" if you feel confident that it will be near perfect, or you could shoot for the middle slope of 3/8"/ft.

One thing I will weigh in on in the Laticrete vs Schluter debate is that with a paint on system there's a user error aspect to it, as well. So when you paint on a membrane you have to make sure you get it even throughout. It only takes one spot to screw up the whole thing. I'm not saying that a sheet membrane can't be screwed up, but you be confident that the sheet is the right thickness throughout.

Lastly, I did a linear drain shower where the drain did not go wall to wall. You can see in the photo the little cuts I put on the ends to make sure the water drained properly.

edit: I can only post this blurry photo because for some reason I can't post the photos my photographer took. If you click on the link in my signature you can see better photos.
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Unread 06-09-2012, 11:24 AM   #14
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We're familiar with the 1/4" per foot minimum slope for that application, Jim, but I'm not familiar with your 1/2" maximum. Where do you find that specification?
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Unread 06-09-2012, 12:43 PM   #15
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Quote:
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but I'm not familiar with your 1/2" maximum. Where do you find that specification?
http://publicecodes.citation.com/ico..._27_sec009.htm
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