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Old 07-18-2005, 05:21 PM   #1
lonnyw
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Installing Kerdi system on Cement slab

Hello. I am an experienced do-it yourselfer, however I have never done any tiling and certainly never built a mortar bed shower pan. This forum is a wealth of information and I feel very comfortable taking on this project especially after learning about the Kerdi system. I took out a pre-formed plastic/fiberglass pan and shower tile and existing cement backerboard. It was installed in 1981 and I see no signs of vapor barrier.
1) I am planning on installing a shower on a pre-existing Cement slab. There is a big hole around the drainpipe. It is 12”h x 12”w x 12”deep. Should I fill this hole up completely with cement OR should I fill it with about 6” of pea gravel and then about 2” of sand and then fill the rest of the way with Cement?
2) If I fill the hole level with the existing Cement slab the drainpipe will extend about ˝” above the cement slab. Will this be enough to attach the Kerdi drain? Does the Kerdi drain slip INSIDE the drainpipe?
3) I want to become a member of the Mortar bed installation crew so I am going to build a Mortar bed shower pan according to the Kerdi installation video and all that I have learned from this forum. Since I have an existing Cement slab what if anything do I put over it before I start building the Mortar bed shower pan? I have read about “cold joints” and didn’t think I should just begin laying the Mortar bed on Cement slab. The Kerdi install video shows laying plastic then metal lath stapled to a plywood floor. Is okay to just silicone the metal lath if it can’t be stapled?
4) I am going to attach 3 -2x4s to build the curb. How do I attach the bottom 2x4 to the Cement slab? Do I just use Concrete nails from Home Depot or do I need to get one of those nail guns that take a 22caliber charge?

I await your expert opinions

Lonny
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Old 07-18-2005, 05:28 PM   #2
John Bridge
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Welcome to the Kerdi Shower Club, Lonny.

The drain will actually attach a couple inches below the surface of the slab, so you'll have to figure how to cut the pipe off down in the hole. I do it with a sawsall, but I'm pretty good at it. You might want to pick up one of those wire saws in the plumbing aisle at Home Depot. You will bond the mortar to the slab, so it doesn't have to be a thick bed.

You can fill the hole with anything up to about four inches below the surface. The last four inches should be filled with mud. Of course, you can fill it all with mud, too.
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Old 07-18-2005, 09:58 PM   #3
lonnyw
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Sorry to ask again but want to clarify. Does this mean I should cut the pipe off level with the existing slab and then fill the hole up with concrete up to the same level as the slab (even with the pipe). Could you clarify?

Does the Kerdi drain slip INSIDE of the drainpipe?

How should I attach the first 2x4 for the curb to the cement slab?

Do I need to put down metal lath on the slab before laying mortar bed?

Thanks. This is an AWESOME forum

Last edited by lonnyw; 07-19-2005 at 12:55 PM.
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Old 07-18-2005, 10:13 PM   #4
muskymike
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Hi Lonny, The drain slips over the outside of the pipe. I use a hammer drill with a 1/4" masonary bit and use either 2, 16 cement coated spikes together or use concrete anchor pins. You can use some construction adhesive too.
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Old 07-19-2005, 06:15 AM   #5
John Bridge
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You won't back fill the hole (at least not all the way up) until the drain has been attached. You have to pack the mortar in under the drain from the edge. Since the mud or fill will end up higher than the drain connection, you can't do it beforehand. I'll find a picture.

I recommend you use bricks for the curb. Cement them to the slab with thin set. I have had problems with wood curbs drawing moisture out of the slab and swelling up. Bricks are the best way to go over a concrete slab.

This drain was set with the bonding flange edge about a half inch above the surface of the slab. I filled the hole and supported the drain by shoving mud in and under from the drain perimeter with my fingures. It's the only way I could make sure the mud was fully packed.
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Old 07-20-2005, 03:08 PM   #6
lonnyw
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Thanks. I have ordered your book from Amazon and will order the Kerdi materials from Tile-experts.com .

I've read all of the threads on installing CBU vs Drywall with Kerdi. I think I'm going to install Kerdi over CBU even though I understand it is completely unneccessary. I guess being a do it yourselfer, I'm thinking even if I made a mistake installing the Kerdi on the Walls and water gets through to the CBU it is better than getting to drywall. (Especially since I just tore out CBU with no vapor barrier). I'm an optomistic person but figure just in case, better to have CBU. I also understand that I need to spray the CBU with water so as not to suck the moisture out of the thinset.

I'm thinking ahead and have a few more questions:

1) I am going to install a "quickshelf" http://www.quickshelf.net/install.html for shampoos, etc.. The instructions say I can install the quickshelf before or after installing the CBU. What would be the best way with Kerdi? Should I install the quickshelf over the CBU and then install the Kerdi over the wall as usual over the flange of the quickshelf?

2) When I get to installing the Kerdi drain. Does the adjustment collar lock it place? Does the top part of the drain sit "on top of the tile"? What keeps the top of the drain from sliding all the way down to it's lowest position?

3) I am going to install 12"x12" travertine tile on the Walls and 4"x4" on the floor of the shower. I asked the guy at the tile store how much space should be between the tiles for grouting. He said that I could butt the tiles as close together as possible and then grout. This doesn't sound right to me. Is there a MINIMUM space for grout allowed. I'm worried that while butting the tile closely would be easier for me, but will the grout adhere or will it crack and fall out quickly?

I have been reading the posts in this forum for the past few days and am amazed at the wealth of information. As a do-it-yourselfer, I appreciate the ability to talk with experts who are actually out there do this stuff.

Thanks,
Lonny
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Old 07-21-2005, 04:36 PM   #7
John Bridge
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Hi Lonny,

The Quick shelf looks like the flange will protrude above the backer board and get in the way. I like the Pro-form shampoo recesses from Noble Company. They can get them to you pretty quickly. http://www.noblecompany.com

Ultimately, the Kerdi-drain is supported by the thin set and grout that ooze inderneath is. It is rock solid once set.

I'd say the minimum spacing is 1/16 in. No way should anything be butted together in a shower. You need a place for the grout.
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Old 07-21-2005, 06:25 PM   #8
lonnyw
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Thanks John.

Since I already have the Quick Shelf, should I install it prior to the Backerboard and then Kerdi over where the backerboard covers the Quickshelf. I'm more concerned with the bottom of the Quickshelf where the backerboard covers the quickshelf. I figure if I overlap Kerdi/Kerdibank at these overlaps it should be fine

Anyone else out there used a Quickshelf and Kerdi?

Lonny
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Old 07-23-2005, 09:42 AM   #9
cindy lou
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Question

Hi All,
Thanks for the help so far, I have found this thread which is pretty similar to the one I started, and I am now in Kerdi Drainville. So, probably a very silly question. When I have everything lined up at the right height, do I glue the Kerdi drain on my 2" pvc drain pipe? I am using the Schluter pan on a cement slab. Cindy Lou
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Old 07-23-2005, 02:48 PM   #10
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Yes Cindy, the Kerdi drain will be glued to the 2" PVC pipe coming up from the trap. Don't forget to use the purple PVC primer first, then glue.

Don't know anything about the Quick Shelf unit Lonny. However just by looking at the pictures on their website my guess would be to install it into the wallboard or CBU recess, then Kerdi the walls wrapping same over the Quick Shelf flange and well in to the sides, prolly all the way to the back. I'm assuming the Quick Shelf unit is waterproof and Kerdi need no be applied to the back of the unit.
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Old 07-23-2005, 06:39 PM   #11
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Yeah, Mike's take is reasonable. If you are using large tiles and you use plenty of thin set behind them, they'll probably clear the flange either way. Smaller tiles would be a problem, though.

Hi Cindy,

Don't remember whether I've welcomed you, so welcome.

Now get onto your own thread so we don't lose you.
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Old 07-27-2005, 12:22 PM   #12
lonnyw
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Thanks. I'm guessing that if my drain pipe is (Black) ABS pipe then I should order the Kerdi ABS drain
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Old 07-27-2005, 12:31 PM   #13
MarcusEngley
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You got it Lonny...
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