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Old 12-17-2007, 12:25 PM   #1
Join Date: Dec 2007
Location: Ohio
Posts: 12
nailing down details for kerdi shower system

Questions for the kerdi experts

So, I’m going to try to get a good jump on my shower over the holiday break, since I have about a week & a half off work, and am putting together a detailed list to follow so we stay focused and don’t skip any steps. Do you guys mind taking a look at it and telling me if I’m on/off track, something’s missing, etc.? I bought John's book and have gone through lots of postings both here & at gardenWeb, but there are a few lingering details that I’ve bolded & bracketed below…

Thanks so much


(cross posted on gardenweb forums)

This will be a 42x42 shower in a new alcove. I plan to put in a framed pivot or hinged door with a panel.

Facing the alcove, the panel will be to the right, about 16” or so wide; the door will fill the rest of the entrance, opening at the left end of the alcove.

Working counterclockwise, the right side wall is an existing wall framed with 2x6’s and will have the plumbing – supply lines to a diverter valve/mixer, and lines up to a traditional shower head mounted on that wall at ~7 feet, and to a rain showerhead in the middle of the ceiling. [this will be running through an attic space – any tips on making sure this does not freeze? I live in Ohio]

The back wall is shared with an insulated garage. I plan to put 2 pre-formed niches next to each other near the left corner of this wall, as well as the smallest Better Bench in the far left corner to use as a foot rest.

The left wall will be made out of a commercial metal stud system since we have such a narrow space to fit it into. It will have only tile plus the end part of the door frame, I’m assuming (I don’t know details about these doors yet)

We will be using the Kerdi shower kit, including the sloped pan, drain, and curb.

I plan to use 6x6 glossy ceramic tiles on the walls, and am trying to find matching 2x2 floor tiles for the shower floor. In case it matters, we plan to use ditra on the bathroom floor with 12x12 ceramic tiles.

Here’s my proposed process…

1. frame the walls and include wood for future grab bars [any suggestions on where to put these?]
2. screw cementboard (durarock) to framing - [do we tape the seams? I read that this would add unnecessary thickness] [also, how far down should the durarock go?]
3. cut holes in the durarock for the valve assembly and the 2 niches
4. attach valve to the roughed in plumbing
5. sand down flanges on niches so they are flat
6. attach niches to durarock by applying kerdiFix to the back of the flanges and putting them into the precut holes
7. starting at the far right edge, where the panel of the door will eventually be attached, dry-fit kerdi to go from just below top of tile down to [how far down do I run the kerdi, given that we will be using their pan?] Cut a hole just smaller than the valve assembly.
8. use a level/plumb line to mark with a sharpie a line from top to bottom at ~ 41” wide (though for me this will be easier since my walls are only 42” apart, so I may just let the wall be my guide)
9. mix up some unmodified thinset [any particular brands you guys are fond of?]
10. mist water on the durarock
11. apply the thinset to the wall ~ 41” wide & as high as the kerdi will go. [what size trowel & notches do you recommend?]
12. apply the piece of kerdi, from top to bottom, and lightly press it all over. Attempt to attach kerdi to valve assembly with kerdifix if possible; make sure kerdi will be completely under the final valve trim and sealed to the trim with the foam provided on the trim piece.
13. go back over the kerdi, top to bottom, and press it into the thinset so that no bright orange spots remain. Smooth out any lumps/valleys under the kerdi, and feather the thinset if it comes out from under the edges
14. this will put us about 2.5” from the back right corner. I think it would work best to skip over the corner and use a full piece of kerdi on the back wall, and the left side wall, then do the corners with overlap.
15. on the back wall, dry fit kerdi and cut holes smaller than pre-formed niches’ flanges.
16. mix up thinset; mist walls; apply thinset; apply kerdi and attach to niche flanges with kerdifix; press into thinset; fill gaps, etc. [do i have to make sure to use the outside corner pieces of kerdi with the premade niches? Or do I just need to be sure the flanges are fully covered?]
17. repeat for left side wall, running kerdi out to where tile will end in doorway
18. on the two back corners, this will leave us with about 3” on each side wall (right and left) and about 1.5” on each end of the back wall.
19. cut kerdi to cover the 4.5” remaining, plus 2” extra overlap on either side, which equals 8.5-9” wide pieces of kerdi for each of the back corners
20. mix thinset; mist corners; apply thinset; apply kerdi

that wraps up the walls… I think we should do the pan next, though I suppose I may end up tiling the walls next, depending on my friend’s availability & how confident I feel with the pan assembly. [If I tile the walls before the pan is placed, how do I know where to put the bottom row of tiles?]

21. cut the 48x48” pan equally on all 4 sides (3” each side) so it measures 42x42
22. cut the 48” curb by 6”
23. dry fit and mark/cut hole for drain
24. apply thinset to floor
25. put pan into thinset & ensure coverage
26. cut first piece of kerdi to size, including drain hole, and second piece of kerdi to overlap first
27. apply thinset to pan
28. set kerdi drain
29. more thinset over drain fleece
30. apply kerdi & secure into thinset
31. apply thinset where curb will be placed, on the floor & walls [where exactly does the curb go? Does it sit on/in the pan, or outside of it/next to it?]
32. place curb
33. dry fit kerdi over all exposed edges of curb
34. apply thinset to exposed edges of curb
35. apply kerdi & secure
36. use premade kerdi corners where curb meets wall (x4) and where pan meets wall/curb (x4) and use kerdiBand along edges where pan meets the walls

I think this would be the end of the kerdi work – whew! Now on to tiling…

Actually, I’ll save that for another post



Last edited by toadangel; 12-17-2007 at 12:29 PM. Reason: clarify title
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Old 12-17-2007, 04:05 PM   #2
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Wow Lisa. That's really long.
Insulate the pipes in the attic.
Go to the Liberry. There's an article about ADA regs that will take you to the page showing grab bar placement.
You tape your CBU seams with alkili resistant tape. Not normal drywall guys tape.
I know nothing about Kerdi though.Hopefully someone who has a good attention span will be along soon.
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Old 12-17-2007, 06:55 PM   #3
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First, forget the cbu...use drywall. It is cheaper, easier to install, and more than sufficient. It doesn't suck up moisture like the cbu does, and is also smoother, lighter, and works very well. You still want to wipe it down with a sponge to get any dust off prior to spreading the thinset. If you use drywall, and you have the tapered edges, you can fill them in with thinset first and let it set so it is flush if you wish. this will make it easier to keep that area flat, but isn't essential.

Using Kerdi, you don't need to tape the seams...the Kerdi is more than sufficient to hold things together.

When embedding the Kerdi, don't try to taper the thinset, just press out any excess at the corners and reuse, or discard depending on how old it is. Once you've got it stuck, work from the middle out so you can actually get the excess thinset out without making bulges or leaving air pockets.

If you can find it, DitraSet thinset is very nice.

The curb goes outside the pan, not on it.

While expensive, Wing-Its fasteners for grab bars are really nice. They are certified to hold 300# without blocking when used in a tiled wall. Blocking is cheaper and is great if you plan ahead properly. Use SS screws so yo udon't end up with rust.

Run you pipe for the rainhead right above the ceiling, then cover with the normal attic insulation. If you have to cross joists, consider relocation of the run. Being that far from the ceiling means no room heat to keep it from freezing. Also, consider a slight slope so any water will run out once you turn the valve off.
Jim DeBruycker
Not a pro, multiple Schluter Workshops (Schluterville and 2013 and 2014 at Schluter Headquarters), Mapei Training 2014, Laticrete Workshop 2014, Custom Building Products Workshop 2015, and Longtime Forum Participant.
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Old 12-17-2007, 08:13 PM   #4
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what Jim said about drywall. CBU is a PITA for a lot of reasons and totally not necessary for Kerdi.

Kerabond is also nice to work with.
Do NOT use CustomBlend.

The bottom row of wall tile goes up last. Take into account the thickness of the tray and floor tile, then leave just a tad less than the width of a tile for the bottom row. Yes, you'll have to trim - that ensures no slivers at the bottom. If you try to get exactly the size of a tile you'll never do it, and you'll also have no way to adjust if things aren't quite straight (and since you are trimming the tray you can bet on it).

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Old 12-17-2007, 08:44 PM   #5
Kirk Grodske
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Go to the Schluter site and watch the installation videos. If you already got the drain and shower kit, a DVD is in there, watch that instead. Watch it a minimum of two times.

It will answer most of your questions and show you how it should go. Then come back with the remaining questions.
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Old 12-17-2007, 09:12 PM   #6
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[this will be running through an attic space – any tips on making sure this does not freeze? I live in Ohio]
I would not recommend running the pipe into the attic space. You should drop the ceiling with some 2x4s or 2x6s and run the pipes for the rain head there. That way the pipes remain in the warm part of the house and you don't have to worry about warm humid air escaping into the attic space.

You need a CONTINUOUS vapor barrier on the warm side of insulated walls and ceilings, be it the kerdi or 6 mil poly.

Last edited by ckl111; 12-17-2007 at 09:23 PM.
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Old 12-19-2007, 10:01 AM   #7
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thanks much guys - i appreciate the time & advice
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Old 12-19-2007, 10:17 AM   #8
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I think you will be okay with the line in the attic - just make sure that you only have insulation above the pipe, even if you have to box around it. This way, the heat from the room will work its way up to the pipe and keep it from freezing. However, I would suggest you use PEX tubing if approved in your area. PEX can handle freeze/thaw without splitting. You can get this at Lowes (they carry it in Cincinnati area stores). You will have to buy the crimping tool, but it is simple to use and works great. The only place you can't use PEX is from the valve to the tub spout because it will have just a bit too much restriction (not an issue for your case).

Have fun!

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