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Curbless showers

DoRight | Posted in Construction Techniques on January 28, 2015 10:28am

Are there any code requirements for curbless showers?

Secondly, some general questions and solisitation (spelling?) of advice.

I have framed a 4 foot by 7 ish shower space with a 30 inch entry on the 7 foot long side and have notched the joist to recess teh MUDDED shower by 2 inches. Therefore, I should be able to build my mudded bas up by about 2 and 3/8 inches.  I say 2 and 3/8 and not 2 inches because I will be adding cement backer board in the rest of the bathroom adding 3/8 inches to teh 2 inch  recess.  I should get about a 3/4 inch pitch to teh drain.

Anyone see any problems so far?

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Replies

  1. gfretwell | Jan 28, 2015 11:07am | #1

    Notched 2" out of the joist?

    Notched 2" out of the joist? What is going to hold this up?

    1. DoRight | Jan 28, 2015 04:05pm | #2

      Well

      The span is less than 11 feet.  An d...oh .... the joists are 2 x 12, now less two inches = 2 x10 on a 11 foot span.

  2. renosteinke | Jan 29, 2015 11:51am | #3

    Lots of Surprises

    Not every law needs an inspector for enforcement.For example, gravity works, whether or not there's an inspection!

    Curbless showers have a few code issues Your plan might have a few more.

    The first code issue is the result of asking:What happens if the drain gets plugged?  This is the reason for the requirement that shower pans be tested for leaks to a certain depth of water. That is, the plumber blocks the drain, the pan is filled to the required depth (2"?) and it sits long enough tosee if it leaks. That's hard to do if there's no curb.

    With this in mind, curbless showers often have a second drain required, as a 'back-up'should the first be plugged.

    A possible solution is to have a curb made of soft foam with a tough rubber jacket; such is used in industrial chemical storage areas. Wheels easily pass over it, yet spills are contained.

    I don't like your cutting the joist at all. I have yet to find a house that was built using anything but the smallest possible joists. For a shower, even code-compliant framing concerns me.

    Why do I worry? Because the less support the floor has, the more it will bend /bounce / flex. This sort of action is death to tile and masonry. The situation is made worse by the weight (tile, water, etc) carried by the floor. The bath floor needs to be STIFF. Flexing -> cracked thinset -> leaks -> rotted floor.

    1. DoRight | Jan 31, 2015 01:29pm | #10

      wow!

      so 2x10s on 16 OC spaning less than 11 feet is not good enough for a tiled shower.  Never heard of such a thing.  Not a 300 pound cast iron tub, but a shower.  WOW.

      1. renosteinke | Feb 03, 2015 04:38pm | #15

        Where's the 2x10?

        It's not a 2x10 after you notch it!

        Weight? Add up the tile, tile board, etc., for a 40x 50 walk-in shower, and I suspect you'll have more weight than that iron tub. (Much to my chagrin, tube are typically set directly on the subfloor, with no finished floor under them).

        Nor do we know if one joist is being butchered - or ten. Code rules regarding notching have been around for decades; I can't help it if someone is ignorant of something so basic.

        We're not worried so much about 'collapse' as we are about those tiny shifts that happen as every floor flexes, with every footfall. Even a concrete slab flexes. The goal is to keep that flexing well under the amount that will cause mortar / thinset / tile to fail.

        Naturally, if the OP wants to have a linoleum floor, the thing can flex like a trampoline and survive. Masonry isn't nearly so forgiving.

        Masonry failures are also often concealed failures. For a considerable time the microscopic cracks will let water seep through, rotting the sub-floor. By the time you have a loose tile, you have a major repair necesary.   Your job is only as good as the base under it.

    2. DoRight | Jan 31, 2015 01:33pm | #11

      What if the drain plugs?  Gee, I suppose there are some morons who take a shower, thave the drain plug, and they don't know how to turn the water off, so they let it run and call a plumber.  I will take that under advisement and check the IQs of those involved with the use of this shower.  Thanks for the heads up.  Keep teh thoughts coming, I never would have thought to look into that.  This is exactly why I love this board so much.

  3. sapwood | Jan 30, 2015 11:34am | #4

    I've built three curbless showers in two different states. In neither case did the local inspector care about a two inch depth to drain requirement. Nor did either inspector require that the base be leak tested. For my part, I fail to see any practical reason for such a requirement in any case. The water is only on in a shower when it's being used. (At least this is the case in my house.) If the drain were to clog, one would simply turn off the water. 

    The building of a curbless shower almost necessitates modifications to the floor system. Its not rocket science. Simply reinforce the joists where needed. 

    1. renosteinke | Jan 30, 2015 01:55pm | #6

      Multi-State Incompetence?

      I see that the codes have the following requirements - requirements, not suggestions- for showers:

      1) Slope of at least 1/4" per foot minimum ... considerably more than the 3/4" over seven feet the OP claims. (IRC2709, UPC 411)

      2) Minimum 2" curb (IRC 2709, UPC 411), and,

      3) Pan filled and inspected (IRC 2503,UPC 712).

      Note that part of the inspection is to ensure that every point of the pan flows to the drain, and that no 'pockets' remain.

      As far as notching lumber is concerned, there are specific requirements for that. Notches are restricted as to size and placement. For the OP's job, he might be required to install additional piers or a steel beam under the notched joists.

      I continue to be amazed at the folks who consider "I got away with it," "well, it worked," and "The inspector didn't catch it" to be the definition of FINE homebuilding.

      1. sapwood | Jan 31, 2015 12:10pm | #9

        IRC P2709.1 Construction begins with the word where.

        " P2709.1 Construction. 

        Where a shower receptor has a finished curb threshold..."

        So, if a shower has a curb then it has to adhere to the 2" depth to drain requirement. If the shower has no curb, the requirement doesn't apply.

        1. User avater
          Mongo | Feb 03, 2015 03:55pm | #14

          UPC a little different

          I don't have the pumbing code in front of me, but when I looked at this for the first time years ago the language was slightly different. At least the version my locale uses was.

          The plumbing code stated seomthing like "...in no case less than two inches or more than nine inches in depth when measured from the top of the dam, curb, or threshold to the top of the drain."

          The shower may not have a vertical dam. It may not have a typical curb. But my AHJ considered the shower entry, or the tile break from flat-to-sloped, to be a "threshold" and wanted a 2" drop from that threshold location to the top of the drain. 

          Since curbless have become more common and trench drains along with them, code interpretations regarding curbless showers and linear drains have become a bit more transparent, but they're still difficult to reference online due to state and local variations.

          Comparing UPC, IRC, etc, can result in conflicts.

          The first time I built a curbless I had to get it aproved via the "alternative methods" provision.

      2. DoRight | Jan 31, 2015 01:34pm | #12

        OK, steel beams?

        Steel beams for a shower.  Nuff said.

    2. DoRight | Jan 31, 2015 01:44pm | #13

      thank you.

      Nice to know steel beams and more peirs are not required.  LOL.  I am in hesterical laughter over those suggestions.

      As for water testing. You build a presloped mud base, tapered out to say 1 inch at the outside edge, lay your membrain on top.  If I have notched down 2 inches and have backer board in the main bath area, the membrain has to climb up another 1 1/2 at the entry point of the shower. That should be a pretty good depth for water testing.

      All said I will ask the inspector what he needs for a test.

      On this board I wished for a starting point and to see if I missed anything obvious.

      Thanks for your thoughts so far.

  4. User avater
    Mike_Mahan | Jan 30, 2015 01:21pm | #5

    Just be sure that a curbless shower drain is not the lowest point in the system. If the main sewer pipe gets plugged the low point is where the sewage will come out. A bath tub is best to contain the over flow. That way you can  smell it before it goes everywhere.

    1. renosteinke | Jan 30, 2015 01:59pm | #7

      Interesting Idea

      I had never thought of this concern.

      With the bottom of the tub an inch or two above the finished floor, I see a real challenge in putting this into practice.

  5. User avater
    Mongo | Jan 30, 2015 08:29pm | #8

    Code requirements...

    Part of the code has been mentioned:

    Pitch 1/4" per foot minimum, and 1/2" per foot maximum.

    With the drain covered, the pan needs to hold a minimum or 2" depth of water over the drain before water reaches and non-protected part of the room.

    Techniques?

    Use a topical membrane. Run the membrane out onto the bathroom floor a few feet outside of the shower entry.

    Use a capillary break at th entry change-of-plane to prevent moisture from wicking into the dry area of the room.

  6. wmheinz | Feb 04, 2015 01:34pm | #16

    On the right track...

    First, cutting the joists..since you had the luxury of starting with 2x12's and the span is only 11', the remainder of the joist should be adequate...especially if the shower is located anywhere near one of the bearing points.  There is a misconception that notching 2" out of a 2x12 leaves the same structure as a 2x10 - the notch actually weakens the joist at the corner of the cut... I always 'notch' mine using a 3/4" spade bit at the corner before making the cuts, then cut to the curve of the hole.  This leads to almost a 100% structural integrety of the cut.  Square cut outs are also prone to being over cut - causing this notch to weaken the joist even more.

    Slope... I probably would slope it 1" overall..assuming the drain is in the middle of the pan....3.5' (half of 7) @ 1/4" per foot would be 7/8"...much more than that and the side slopes get pretty steep.   

    Curb height - I have installed and specified dozens of curbless showers and have never had one questioned...nor have I ever had one overflow.  I see no difference between this and a floor drain....there's no way to build a curb around a floor drain to test it???   I suppose an additional floor drain installed somewhere in the bathroom could be done as backup plan if you are worried about an overflow...I've never felt the need....

    Mudset thickness...I think you might be a little light on your thickness near the drain...make sure you have adequate thickness to maintain the structure of the pan around the drain...get that too thin and you risk cracking.  If it were me, I would notch the joists at least 2 1/2" and reinforce them if needed.  Or install ledgers on each side of the joists and set the plywood sheathing between the notched joist and flush with the top of the them (I've done that where we had limited joist heights to work with).

    Just my thoughts....

    1. DoRight | Feb 04, 2015 02:32pm | #17

      Notching

      Thanks wm.  Yes, I hear you about teh notch and round corners.  I did that.

      So what is a typical "pre"slope thickness at teh drain?  Do you taper that to 3/4", then membrain, and then the final mud deck of 1 1/2".  Is the 3/4 inch preslope to thin? 

      Thanks.

      I thought of the idea of scabing on sisters and then recessing the subfloor between the main joists to get the extra depth.  Sure don't really want to do that.  But short of steel beams and extra piers LOL, LOL, I do want the floor stable.

  7. wmheinz | Feb 05, 2015 04:48pm | #18

    On the right track...part 2

    You could just sister the joist with a 2x6 down each side flush with the bottom of the existing joist.  There should be no problem with shear or bending failures....you would be trying to eliminate deflection, and placing more material along the the bottom of the joist would be a help if you need insurance. 

    For all my tile work, I place complete faith in the Tile Council of America Handbook for Tile Installation (https://www.tcnatile.com/handbook-all/910-2014-tcna-handbook-for-ceramic-glass-and-stone-tile-installation.html).  I follow their instructions religiously and have all of my contractor's do the same.  Your local tile supplier should have a copy for you to review/copy)  As far as I am concerned, they are the bible for tile installations!  If you are planning to use the Kerdi type system, their installation method is outlined in B422.  Ive been using Kerdi's system of their presloped drain pan for the last few years and like it a lot - wouldn't use anything else.  See:  http://www.schluter.com/143.aspx about their floor systems.  In their instruction manual, they talk about installing traditional mud bases as well. 

    Good luck....

    1. DoRight | Feb 06, 2015 01:56pm | #19

      Thanks for several of your posts but ....

      Thanks for the links.

      It sounds like you use the foam slope system.  I have thought about that, but seem to think they don't work as well for long showers and are pricey.  I might use one for the master shower which would be used alot, but maybe a fully mudded bed for a guest shower which would almost never be used.

      As for handbooks, it looks like the handbooks are sold so I will see if I can find one on ebay, amozon, or at the library.

      In the mean time ....

      I have been trying to find out how thin or thick the preslope haso be at the drain.  Some internet sites have said 1/2 inch, some 3/4, some don't have a preslope at all (they either then ahve a rasied drain flange (BAD) or recess the drain flange into the subfloor by cuttting the hole with a sloped cut to recieve the flange (not much material left to receive screws, ugh).

      So, I the flange is screwed directly to teh subfloor, the flange is about 1/4 of an inch thick so teh top fo teh flange is 1/4 inch about the subfloor.  Do you scree your mud level with that?  if so that is 1/4" thick.  Or do you scree it proud of the flange (1/2 inch or 3/4 inh) so that the membrain drops hard to the flange? 

      All of this is important and particularly becuase you ahd said my 2" notched joist might not be enough for a curbless shower. I think I had made a mistake in my math.  I think I was thinking 3/4 preslope at the drain and then an 1 1/2 mud base ontop of the membrain, which would be a total of 2 1/4 inches .  BUT HEY!, the preslope is sloped!!!!! Duh.  So 3/4 at drain is 1 1/2 at teh edge plus the 1 1/2 top mud for 3 inches.

      I have options, but just trying to start by figuring out how to set teh drainand how thick the preslope is at the drain.

      Thank you for your patient attention.

  8. renosteinke | Feb 09, 2015 02:44pm | #20

    March 2013 #233: Wide Open Bath

    Cover Story: "Curbless showers are sleek and accessible"

    It should be noted that the FHB article agrees with my comments regarding slope, the need for a stiff floor, and structural support.

    I recently visited a modern truck stop with barrier-free showers. After my shower, I discovered that much of the water had left the shower area,and pooled in the changing area. Now, 1/4" water might not seem like much- unless your clothes are sitting in it!

    That puddle would have been discovered had there been a proper 'flood' test. Sure, it might make someone feel all warm and happy to smugly comment how they would shut the water off if the drain were plugged .... but this same person would have no idea that some of the water was flowing in the wrong direction - perhaps out of the bath and down the stairs (Look, Ma! An indoor waterfall! :D ) 

    Having a secondary drain helps ensure that the water flows to where it's supposed to go. Lacking a curb, it's all too easy for water to wind up on the wrong side of the slope.

    On reflection, it probably makes sense to replace the traditional drain ("round," placed in the middle) with a linear / trench drain placed across the entry. This placement would also allow for a slope to direct any over-spray back towards the shower.

    1. DoRight | Feb 09, 2015 05:34pm | #21

      Truck stop, nuff said

      nuff said.  I don't live in a truck stop, and I don't live with morons.

      In fact I have never had a tud back up either, even with .. how many women using it.

      Live in fear if you must.

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