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Unread 01-23-2013, 09:06 PM   #1
Freddie44
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Kerdi Drain and Curbless shower

Hi all,

Starting to work on bathroom remodel. So far I have determined that my joist arrangement is rated above 1 / 720 deflection and my current floor is 5/8" OSB which I will be replacing.

First I'll describe my plan. Bathroom floor to have 5/8" plywood put down to replace OSB followed by 3/8" plywood for additional support then in floor heating, Ditra and then 1/4" tile. All this puts my bathroom floor at 1 5/8" above the top of the joists AND 1/4" above the adjoining bedroom hardwood flooring.

In the shower area I would like to put in a curbless shower of about 40" x 40" in size with a Kerdi drain in the middle. To do this I would drop the 5/8" plywood subfloor in that section down so that it is level with the top of the joists. From what I have been able to figure out it appears that the Kerdi drain minimum height from top of subfloor to top of drain is 1 3/8". Then add on say 3/8" of slope height to that and I'm at 1 3/4" above the joist top at the shower edge.

Shower edge is 1 3/4" above joist and bathroom floor is 1 5/8" above joist and I'd like to slightly slope (say 1/8" for 1') just outside the shower door so that water just outside the shower runs back in to it rather than sitting on the floor. So that gives me now 1 7/8" vs the 1 5/8" or 1/4" difference in height. So, I have 2 options that I see. Raise the height of the entire bathroom floor and deal with the 1/2" difference at the bathroom entrance OR lower the Kerdi drain down a bit lower and deal with a much smaller difference at the bathroom entrance.

My question, is there a way to drop the top of the Kerdi drain down another 1/4" or so by either lowering the floor even more just around the drain (which might then not provide enough mortar below the drain edge or below the kerdi membrane) OR using some different type of mortar to reduce the amount of mortar below the kerdi drain?

If anyone has any ideas that would be much appreciated. I know this can easily all be done with a curb but I'd like to not have to go that route; my wife is really set on having the look of a curbless shower. Oh...btw I'm in Canada and we have no code requirement for the 2" of water hold above the drain.

Fred
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Unread 01-23-2013, 10:21 PM   #2
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Fred,

You lost me a little on the math there, but its close to my bed time. I do better with diagrams.

Can you install sister cleats on the sides of the joists to inset the first layer of plywood?
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Unread 01-23-2013, 10:28 PM   #3
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like this
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Unread 01-23-2013, 10:31 PM   #4
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Inset the plywood between the joists. Yes that is my plan and was built into the numbers.

Sorry, yeah there was lots of math. Basically trying to find out how to lower the kerdi drain as low as possible to try and keep the exit from the shower lower which in turn means with a smooth transition from the shower to the bathroom that I can keep the bathroom floor lower and limit the transition between the bathroom floor and the bedroom floor.
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Unread 01-23-2013, 10:37 PM   #5
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Concerning your drawing, in the shower area I was going to drop 2 layers of plywood in between the joists but in the bathroom area the 5/8" and 3/8" plywoods would both be on top of the joists.

There would be 1" of mortar on top of the top piece of wood between the joists and on top of the joists in the shower area. Then add 3/8" above that to the top of the drain (3/8" for thinset and tile) then slope up to edges of shower area.

I'll try to generate a picture of what I'm thinking tomorrow at some time. Off to bed for me as well.
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Unread 01-23-2013, 10:51 PM   #6
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It looks to me that you will have a little more than 1 5/8 thick if you add the bonding mortar into the equation. Bonded mortar for covering heating wires , setting Ditra and setting the tiles.

Aside from needing a maximum of 3/4 inch thick from the top of the Kerdi roughing drain to the top of the joist to actually come close to the target ( 1 3/4 total thickness ) and assuming you have the right configuration ( room plan and location of the door needed ) to create a continuous slope with necessary pitch for the entire surface to drain into the Kerdi drain ...... how will you and what materials will be used to accomplish the preparation of the floor to be ready for tile installation ?
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Unread 01-23-2013, 11:02 PM   #7
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Here's the Layout. Sorry for the crappy dwg.
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Unread 01-23-2013, 11:05 PM   #8
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Eurob,

I guess I wasn't clear. I don't want to drain the whole bathroom floor to the shower...just 6" or a foot outside the shower door. But I could live without that if it all comes down to it.
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Unread 01-23-2013, 11:39 PM   #9
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Welcome, Fred or Ed. Which is it, please?

I'd reconsider some of your measurements. The minimum rise in slope you can use for the shower floor would be 3/4" for the distance from your drain to the far corner of the shower.

I would never replace a removed subfloor with anything less than 3/4" T&G plywood. Not sure why you wanna remove 5/8ths" subflooring and replace it with 5/8ths" subflooring. If what you have is in good condition, you could install a second layer of 1/2" plywood and have a good subfloor.

I would never use less than 3/4" plywood for a dropped subfloor and be sure whatever you use is oriented with the strength axis perpendicular to the joists.

Some other missing dimensions in there, but I think most have been mentioned.

Make a good subfloor for your tile installation and then make transitions to other flooring as necessary. Not a difficult thing to do.

My opinion; worth price charged.
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Unread 01-24-2013, 09:23 AM   #10
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Ed,

I also plan, or at least want to, do a curbless shower and have been noodling on it for months (even as I complete my kitchen back splash tile job). My idea is the same as yours, start the floor slope 5 or 6 inches outside the glass doors so any splash runs back into the shower. I do have the 2" height requirement though.

Have a look at this thread from the Pros hangout. http://www.johnbridge.com/vbulletin/...t=98038&page=2

On the second page the craftsman sloped the shower floor along its length back towards,, and within about 4 inches of, the rear wall, then installed a trough that slopes to the drain. In other words, the entire main floor slopes to the trough, then the trough slopes to the drain.

My hope is that this arrangement will end up with the drain placed low enough that I can then get by with almost no change in height of the rest of the bathroom floor and no more than a 1/2" or so threshold/transition to the bedroom.

Dan
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Unread 01-24-2013, 09:41 AM   #11
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In this shower we added more joists in the shower area to raise the deflection to 1800+ and solve some structural issues of rotted wood, cut joists and poor spacing. This allowed us to angle the top sides of the joists in the shower area to achieve the needed slope. The linear drain is placed at the far wall, about 1.5" below the main bathroom floor. The break point in the floor is at the shower door. (if there ever will be a door, they are still deciding)
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Unread 01-29-2013, 06:38 PM   #12
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So it sounds like, from all these posts, that it is going to be hard to match up the existing bathroom floor with the shower exit without a curb. Is that the general conscensus? Curbless is out?
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Unread 01-29-2013, 07:29 PM   #13
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we did a curbless handicap shower for a customer a few years ago in Tampa.
this house wasn't a slab home so we cut down the joist 2".
sistered them on both sides and bolted them together.
did a mud bed, waterproofed it with Schluter Kerdi & Ditra.
and tiled it. works great and they can spray down their child in the chair.

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Unread 01-29-2013, 07:35 PM   #14
Freddie44
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Not interested in cutting down the joists. Too big a job. So without doing that I assume there is no way to get the top of the Kerdi drain below 1 3/8" above the top of the joists?
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Unread 01-29-2013, 07:59 PM   #15
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you can mud your whole room floor higher.
but I think your looking for an easy way and there isnt going to be one.
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