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help -- large format floor tiles with linear drain

Posted by jing_2009 (My Page) on
Sun, Feb 2, 14 at 11:58

I'm doing a mater bathroom with porcelanosa large tiles and a linear drain.

The shower is curbless. There will be one glass panel set on the left side, between the shower and the toilet. Drain is set by the right wall. The tile size is 13"x26". Now the tile guy did the following: he left a 3/4" gap by the threshold; and the grout lines are lined up every other row for the three rows close to the drain, and then follow a stagger pattern for the rest.

His explanation is that he had to have the gap in order to make the top of the tiles smooth because of the sloping. He did not explain why he changed the grout line pattern.

This floor just looks too awful. I want to see a consistently set floor, and without a gap at my threshold. My GC said it is just very difficult to slope the large tiles, so even if we start the tiling all over he doesn't know how he can make it work. He is also worried that ripping out the tiles now may damage the wedi board and the electric radiant heat we set beneath. My floor is already raised by 3" which I believe is more than enough for the slope.

Any advice? Thanks in advance.

This picture shows the gap at the threshold


Follow-Up Postings:

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RE: help -- large format floor tiles with linear drain

This picture shows the other end of the row with the gap as well as the drain


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RE: help -- large format floor tiles with linear drain

And a third picture with the inconsistent grout lines


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RE: help -- large format floor tiles with linear drain

That drain location requires a compound slope (requiring varying grout widths to achieve) rather than a single slope to the drain. The design was flawed from the beginning. If you wanted curbless with a single drain, the drain location would have been along the wall pepindicular to the current location, and if the shower is less than 4'wide, then the whole room should be treated as a wet room. What you have won't work technically. It's beyond a tile spacing issue. It's a won't drain right and might flood your house issue.


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RE: help -- large format floor tiles with linear drain

hollysprings -- thanks for the reply. Would you elaborate what needs to be done? The prospect of flooding is very scary...The original design was to have the drain against the wall as you suggested, but the wedi pre-fabricated board with drain is too wide so my GC suggested to move it to the current wall. I attach the dimensions of the bathroom.

This post was edited by jing_2009 on Sun, Feb 2, 14 at 13:26


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RE: help -- large format floor tiles with linear drain

Is it because it is curbless that it needs a compound slope? We have a shower in roughly the same location in our bathroom, with the linear drain in the same place, but curbed, and there's only a one-way slope and it's working perfectly, so I was just curious about the technical issue.


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RE: help -- large format floor tiles with linear drain

Yes,it's because it's curbless. With a curb, the entire plane of the shower can be a flat surface draining towards the rear like that and the room itself can be nother flat plane that is level. The curb hides the transiton point between the two.

Where that drain is placed doesnt work with curbless. Curbless either requires two separate planes (the shower and the rest of the room) with an obvious break at the join between the two where the two planes intersect, or the entire room has to be a wet room with a single sloped plane towards the drain that is located allong one entire wall. The drain located where it is requires a front to back and left to right slope of tbe floor, and thats one of the reasons for te differing gaps.

The entire thing needs to be torn out and started over.


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RE: help -- large format floor tiles with linear drain

Thank you hollysprings.

I don't understand, though, why having the drain by the other wall would make a difference. Either way, the tiles will have to have a compound slope. BTW the shower head goes above the current drain, and the glass panel will be installed opposite the drain, roughly along the dotted line for wedi.


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RE: help -- large format floor tiles with linear drain

With the drain on the other wall, and taking up all of that wall space, the entire room can be one single plane sloping towards that drain. It requires raising the floor on the side opposite, or cutting into the joists to lower the shower area, or both. Then waterproofing under it all, as a wetroom needs to be done. If you want to use large format tile, and don't want a seam all the way across at a transition area, that's what has to be done to get both the look that you want and the correct slope and waterproofing.

Otherwise, you need to change to a smaller tile or/and be OK with the visible line where the two planes intersect. And the shower has to be a minimum of 48'' wide with a 1/2" slope to be able to pass the pan test holding the required amount of water with no curb.

Whoever designed this is in error, and it shoud be on them to correct it. Education is expensive.


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RE: help -- large format floor tiles with linear drain

Is there a reason they couldn't have had a tile pattern similar to the one below? A simple offset pattern, the offset can be tweaked as needed. But essentially it's an offset with a break line where the slope in the floor starts for the shower.

The green line represents your glass wall between the shower and the toilet.

The blue dashes represent where I'd start with whole tiles. This way you'd have two runs of tile with a natural break right at the shower threshold. The middle tile at the threshold would have to be cut to make the slope, that cut line is shown by red dots.

The arrows represent tiles that are sloped to the drain. Only the tiles inside the shower are sloped. All others are flat.

There are rough measurements on the right side of the drawing. They would have the front edge of the drain 4" off the back wall so two full 26" tiles could make the 52" run from the drain to the threshold.

While it's not a measured drawing or done to scale, this rough design probably would have been my starting point for a discussion about layout.

Had you wanted a floor with a half-tile offset, for a nice floor pattern I probably would have recommended changing the demensions of the shower by a coupe of inches in each dimension. For example, lengthening the shower a couple of inches to reduce the floor between the shower threshold and the door to get 1-1/2 tile lengths or 39" of floor between the door and the shower threshold instead of the 41-3/4" you have now.


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RE: help -- large format floor tiles with linear drain

Thank you so much for your thoughtful reply, mongoct.

I was not clear: the shower is to be doorless as well, so there is no threshold and the glass panel along the green line would be the only separation the shower has from the rest of the room. My GC's argument is that then water may get beyond the blue line, and hence the entire floor needs to be sloped.

Is there anyway to slope the tiles correctly with the current drain position? My GC hinted redoing the Wedi would be a major issue.

Would setting the tiles straight without any offset be easier to achieve the slope? If so I'll be perfectly happy with that layout.

The dimensions indeed are a little bit off from what was intended. We were shooting for a width of 42" because my wall tile size is 12"x35". On the other hand, since there was no door/threshold, we could start the slope in this direction anywhere we want.


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RE: help -- large format floor tiles with linear drain

If you stopped that drain up, the resultant pool would not be able to reach 2" high before flooding the surrounding room. That's the standard for code compliance test for a shower installation. curbed or curbless.. The slope can be between 1/4" and 1/2" per foot, which in practical terms means that you need a minimum 4' drop front to back, or left to right, to the drain for that to comply. With the drain in that location, it needs to slope front to back, and left to right. Which won't work for a smooth no break layout.

It also means that, as installed, you'd need a curb to the outside to contain the water inside the shower section. Or, it could be a flat entry, gradually moving towards a 2" curb at the drain end using the tile design that Mongo showed. The only way to achieve that completely flat and smooth laid tile floor with large format without the break between the two sections is to have the entire room slope, as holly says. If you were OK with a single visible line, the drain could move to the other wall, and justnthe shower could be sloped in a single direction towards that drain. But, it would need to be a 48" wide shower to do that.

The whole thing needs to be redone. By someone who understands geometry and plumbing codes.


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RE: help -- large format floor tiles with linear drain

who designed this in the first place ?

did you /contractor know that WEDI can be cut easily to just about any shape and width ?

does the contractor have mud skills - or is that why WEDI was used to begin with ?


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RE: help -- large format floor tiles with linear drain

I called my township and they actually don't require a pan test for curbless shower. They said all they wanted to see is that the floor is pitched in the right direction.

My GC had experience with Wedi before. Our problem this time is that he couldn't get any Wedi with a width (42") that we could fit in the other wall. The overall width of Wedi board is not a problem, the problem is the linear drain is simply too long for that wall. My GC was told that Wedi no longer makes shorter drains than that.

I am really hoping that we could find a solution without having to replace the Wedi and move the drain location.


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RE: help -- large format floor tiles with linear drain

Just because your local code office fails to enforce something is no reason for your contractor to skirt home safety by ignoring a code requirement. It's not a free pass to do it wrong just because someone doesn't check to be sure it's done right. That logic won't fly. Especially with your insurance company if you were to have an issue. Would he really pull the "it's not inspected so I didn't have to do it right" on them? He would have his butt sued until there wasn't one left!


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RE: help -- large format floor tiles with linear drain

I would be interested in clarification on the code aspect of this as well. I understand how the requirement reads. But forgetting the code angle, why is this the rule? What does it accomplish?

It is based on protecting the home in the event a drain is blocked, I get that. It seems to me that it buys a certain amount of extra time before water can leave the room-- the amount of time would depend on the geometry of the room (slope, square footage, etc.) so can't be calculated in general, but if the drain is blocked and the water keeps running, the flooding is gonna happen anyway, correct?

Second question is bassed on the assumption that you somehow block a 4 ft (or whatever) linear drain. How? I don't think I could lay down on it and keep it from draining even if I tried my hardest. I could imagine someone fallling down and blocking a "regular" drain by just sitting on it, but that is a different scenario.

Please tell me if I am missing something here. I'm truly trying to understand the logic of the requirement, so "it's the rule" is not so helpful...

I don't mean the hijack the OP's installation issue and how to fix it, but every time this comes up, I try to figure it out and can't. It seems like maybe the OPs jurisdiction is making their exception because it is a curbless install with a linear drain and they don't see the flooding issue as a realistic possibility either?


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RE: help -- large format floor tiles with linear drain

If the grate were removed, it's certainly possible to block a linear drain at the pipe. That's the concern. It's just a trench to a regular pipe. It's possibly less likely than with a standard center drain, but there is a possibility that someone might be cleaning the drain, step away for a moment, and the cleaning rag block the pipe. Or hang a bath towel up that falls. Or a couple of other scenarios.


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RE: help -- large format floor tiles with linear drain

Why does the city care if I flood my house, as long as I don't live in a multi-unit building?


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RE: help -- large format floor tiles with linear drain

"I was not clear: the shower is to be doorless as well, so there is no threshold and the glass panel along the green line would be the only separation the shower has from the rest of the room. My GC's argument is that then water may get beyond the blue line, and hence the entire floor needs to be sloped. "

I think you described it fine, and I'm pretty sure I understood what you described. I understand the shower is doorless, when I wrote "door" I was referring to the bathroom entry door in the bottom right of my drawing.

When I wrote "threshold", I was simply describing where you go from flat bathroom floor to sloped shower floor. I understand there is no elevated curb to step over. I was describing a "break line" in the tile where the floor changes from flat to sloped.

"My GC's argument is that then water may get beyond the blue line, and hence the entire floor needs to be sloped. "

With the shower head on the back drain wall (in my drawing) you'd get little to no splashing at the threshold which would be 56" from the back wall of the shower. Maybe a few incidental splashes on occasion. But no large puddling. Besides that, in curbless showers I carry the floor waterproofing under the tile out past the shower threshold and onto the flat part of the floor so a portion (or even all) of the floor between the shower threshold and the bathroom door would be waterproofed.

With the drain on the back wall of the shower, you have a bit over 4' of run from the shower threshold to the drain. At 1/2" slope per foot of run you'd get the code required 2" of vertical drop inside the footprint of the shower floor.

"Is there anyway to slope the tiles correctly with the current drain position? My GC hinted redoing the Wedi would be a major issue. "

The problem is trying to make a compound slope with large format tiles. The large flat tiles can't conform to the floor shape perfectly, so you end up with uneven grout lines and lippage between tiles, where the edge of one tile can be slightly higher than it's neighbor.

There is a way to make it work but it would involve a proper layout from the start, I'd have dimensioned things differently, and I'd have used a mud bed with a topical membrane instead of Wedi. It would have required a lot of careful cutting of tile in terms of shaving the edges to puzzle the tile together, all while maintaining the appearance of nothing being cut. Meticulous craftsmanship would be needed.

What you have is a compromised design and layout for the material you are using. Your builder is taking large format tile (the square peg) and trying to stuff it into a poor design/layout (the round hole).

And although you and your town/city inspectors don't seem to mind, he's building you a shower that violates building code. While that may not be an issue now, that could be an issue if you ever sell the house.

Yes, changing the floor pattern to a stacked design could make things a tad easier, especially regarding lippage.


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RE: help -- large format floor tiles with linear drain

Jing we are also currently installing linear drain and large format tile in a curbless solution. Thanks to advice here on Garden Web, I looked carefully at my desired large format tile and spoke with my installer this week as he planned the layout. We also took Mongo's (and other people's) comments to heart and wet down a tile and walked around on it to see how slippery it was or wasn't. We have now decided to keep the larger tiles in the main part of the bath and cut smaller rectangular tiles out of the large ones to go into the shower - better traction / more tactile underfoot, especially as we age. The layout will continue as staggered brick even when the tile changes to smaller format. Folks here led me to make a decision for safety and not upon the love I had for the large format showers I see on Houzz etc. I don't know if a smaller cut of tile will help in your situation as the slope has to be right from the get-go for the drain, but something else to consider?


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RE: help -- large format floor tiles with linear drain

Thanks everybody for the input, especially mongoct -- thank you!

I realize now that I should have insisted in putting the shower and the drain on the back wall. It would have been so much easier and safer that way. -- A tad too late now unfortunately. I wish I had posted in the forum before starting to build.

Lori, I agree with you that under regular use, the 2" drop will not do anything. But then again, under regular use a house will never catch fire, yet the code requires smoke detectors and we generally agree it is a good idea.

One question, what is the building code? Is it supposed to be a guideline for the entire U.S.?

At this stage, looks like correcting my problem will have to involve tearing down the framing, changing the wedi, redoing the radiant heat and redoing the rough-in. Education IS expensive.

divotdiva, thanks for your suggestion. I'm not very worried about the traction under foot, as my tiles are textured and hence has excellent traction. The look of the large format tile is what I was going after at the very beginning. My GC quoted me based on the tiles I selected in combination with a linear drain, curbless shower and radiant heat, so I'm quite reluctant to give it up now.

Another question, I was made aware that the tile guy used thinset to build up the desired slope, and the thinset is as thick as 1" towards the high end of the slope. This I was told is very problematic as it might cause tiles to crack. Is this true?

This post was edited by jing_2009 on Tue, Feb 4, 14 at 11:37


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RE: help -- large format floor tiles with linear drain

"Besides that, in curbless showers I carry the floor waterproofing under the tile out past the shower threshold and onto the flat part of the floor so a portion (or even all) of the floor between the shower threshold and the bathroom door would be waterproofed."

Currently wedi only covers the portion I noted on the drawing. The GC rolled a layer of greenish stuff on the entire bathroom floor which I think is supposed to be waterproof. Would that be sufficient? Do I need waterproofing on the half wall below the window as well?

The photo shows what it looks like before tiling started.


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RE: help -- large format floor tiles with linear drain

The "green stuff" looks like Hydroban. It's a very good waterproofing membrane and it'll provide you with waterproof protection for the entire floor.

If it is indeed Hydroban, I'm somewhat surprised that the entire thing wasn;t done with Laticrete products. Laticrete is the manufacturer of Hydroban.

The floor could have been sloped mud (a fraction of the cost of a Wedi pan), the walls could have been cement board (much less expensive than Wedi board), they could have used a Laticrete linear drain (a 36" linear drain would have fit nicely on the 42" back wall), and then the sloped shower floor and the shower walls could have been covered in Hydroban to match your existing bathroom floor.

"Another question, I was made aware that the tile guy used thinset to build up the desired slope, and the thinset is as thick as 1" towards the high end of the slope. This I was told is very problematic as it might cause tiles to crack. Is this true?"

There are different materials used to set tile. Thinset doesn't have bulk sand fillers that some of the other setting mortars have. Thinset is designed for "thin" setting applications, and without the bulk fillers it's intended maximum thickness is generally 1/4" thick. When setting tile, that means it can be spread with a 1/2" notched trowel, and when the tile is set, the 1/2" high ridges left by the trowel will be compressed to a continuous 1/4" thick finish layer when the tile is set.

Without the bulk fillers, if thinset is used in "thick" applications like your 1" thick depth, as the thinset cures it can shrink. That shrinking can sometimes pull tiles askew. They might have been set straight and level, but you come back the next day to find the tiles out of alignment, or with lippage between the edges of adjacent tiles.

As to the tiles cracking, that could happen. The shrinkage can cause voids in some areas under the tile, or the tile can have uneven bond strengths with the substrate, with the thinset "pulling" more in one area than another as it shrinks while curing. That could result in latent stress within the tile. If there was some other stress applied to the floor at a later date, I'd suppose that cracking could occur.

To build up thicker elevations, most installers use deck mud for elevation and then set the tile over the mud with thinset. Or for an in-between thickness they'll use a medium bed mortar.

You asked about code. As to what code applies, there are indeed different codes. IRC (International Residential Code) is the one that generally applies. If another code applies, it sometimes refers back to IRC.

The two main considerations for a shower are:

1) the floor slope within the wet area of the shower needs to be a minimum of 1/4" and a maximum of 1/2" slope per foot of run.

2) Water containment within the waterproofed area: If your shower drain is plugged and the shower flooded to where you have a 2" depth of standing water over the shower drain grate, the waterproofed area of your shower (or bathroom if the entire room is a wet room) needs to contain that pool of water and prevent it from flooding into the non-waterproofed areas of your house.

A traditional shower curb is what typically contains the 2" depth of flood water. With a curbless, you can see the flood footprint can be larger. Your floor is fully waterproofed with Hydroban and they even carried it up the walls a bit. That's good. They'd also have to make sure that your bathroom door threshold is above that 2" plane, as well as the holes in the floor for the toilet flange, the toilet water supply, etc. They either need to be above the 2" flood plane, or waterproofed to contain the water pool.

Hope that helps.


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RE: help -- large format floor tiles with linear drain

Mongo: "Besides that, in curbless showers I carry the floor waterproofing under the tile out past the shower threshold and onto the flat part of the floor so a portion (or even all) of the floor between the shower threshold and the bathroom door would be waterproofed."

Would you do that on a slab-on-grade as well? The roll-on type? I guess that would prevent water wicking?

Thanks for the diagram, LWO-- I did understand that it was physically possible to block the drain, just seems like it would take some effort, and the 2" still just buys you some time. More depth would buy you more time, someone had to settle on something.

But the consequences of wet walls are not the same as the consequences of a house fire while you're asleep, although I understand your point, jing.


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RE: help -- large format floor tiles with linear drain

"I'm not very worried about the traction under foot, as my tiles are textured and hence has excellent traction. The look of the large format tile is what I was going after at the very beginning."

Me too - ours have texture and are recommended for many applications, but do make sure you test a couple of yours out before you live with them - wet one down outside or in the garage and stand on it. Maybe even add soap. Move around. Bend over and pretend to pick up the soap. I was OK with them but after doing this a couple of times, my husband felt he definitely could slip (especially as we age) on a 12x24 tile. And he's pretty agile. The tile setter and the GC both recommend more grout lines for safety. The shower floor tiles will be cut a little smaller than the average foot size and the rest of the room will remain large format. I LOVE the large format but made the concession.


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RE: help -- large format floor tiles with linear drain

"Would you do that on a slab-on-grade as well? The roll-on type? I guess that would prevent water wicking? "

Yes. I carry it further than required all the time, I'll usually run it a minimum of a few feet past the shower threshold.

I prefer to not tile directly on slab-on-grade. I'll use an uncoupling membrane, usually either either Ditra or Nobel, to isolate the tile from the slab.

If you choose to tile on the slab and simply want basic waterproofing, then yes, something along the lines of Hydroban or RedGard would be perfectly appropriate. HB will give you waterproofing but it is vapor permeable, RG has a lower perm rating and will give you water- and vapor-proofing.


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RE: help -- large format floor tiles with linear drain

Thank you again for the very detailed explanation mongoct.

It is good to know that waterproofing on the floor seems sufficient. About the choice of wedi in the shower area, I think he wanted to be extra careful given the combination of tiles, curbless and the linear drain. I appreciate that consideration.

divotdiva, you are right, safety should be number one priority. We'll test the tiles tonight just to make sure.

I am in two minds about what to do now. It is so expensive to start all over again; on the other hand, patching up mistakes instead of correcting them tends to cause bigger trouble in the long run. I am meeting with the GC tomorrow morning and hopefully we'll figure out a way.


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RE: help -- large format floor tiles with linear drain

One thing to consider, if you keep your tile as is, you can sometimes reduce the visual impact of the uneven grout joints by using a grout the same color as the tile.


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RE: help -- large format floor tiles with linear drain

Thank you mongoct. I do have the matching grout.

The tiles will have to be redone for sure. I checked the tiles again this evening, the lippage is really bad. In a few places it's almost 1/16". That's just accidents waiting to happen. From what you explained before, I suspect it is because of the "thick" set.

Still thinking about whether to relocate the drain.


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RE: help -- large format floor tiles with linear drain

Good luck and let us know what the fix is! I hope you get to use your whole tiles!


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RE: help -- large format floor tiles with linear drain

Yes, I forgot to say good luck with your resolution. I can only imagine how stressful this is for you.


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RE: help -- large format floor tiles with linear drain

Thank you divotdiva and lori! Let me just say that this has already cost me one sleepless night.

Divotdiva, we did test out the large tiles in the shower, and the traction is very good. So we decided to continue with them in the shower.

GC came by this morning and took out the first 3 rows of tiles (the ones in the shower area up to the door). The green stuff is indeed hydroban. Some of the wet bed came up together with the tiles so he'll need to redo those areas. He says he'll grind down the existing thinset and reset the tiles we took out, continuing the stagger pattern of those tiles that are staying. Apparently it is impossible to change to a stacked pattern without tearing down the entire floor.

I've engaged a local design company that is known for doing such modern bathrooms to review this project, and help me to find a best approach at this point.


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RE: help -- large format floor tiles with linear drain

I'm glad that you found someone with experience locally to help you through this. That on site hands on bit can't be overestimated. I only hope your GC is willing to do the corrections that they may suggest.


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