Peter B's Shower Project [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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Peter B
11-02-2008, 07:15 PM
Forgive me if the answer to this is in the forum somewhere, I have searched the forums and haven't found it.

I'm building a shower on an existing ground floor concrete slab. I'm going to use the full kerdi kit. I have removed the existing drain and trap (2" abs) and relocated it to the center of my shower. The new parts are all glued up, except for the riser pipe that comes out of the P trap and that I will glue my kerdi drain to. Before I can backfill the hole and repair the slab I need to glue in this last piece of pipe, and before I can do that I need to know how long the pipe should be.

I have Mike's diagram from his post and it shows pipe from the trap ending 2-3/4 inch below the top of the kerdi drain. The big question is this - how high does the drain sit above the slab if I'm using the Kerdi ST tray (dimension "a" on the drawing.

My Kerdi kit is backordered, and I may not get it for 2 more weeks, so I can't just pop out the middle spacer part and measure it.

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Peter B
11-02-2008, 07:55 PM
I moved the drain in my shower, so I have a hole, 11" x 14", to repair in my concrete slab floor. The hole was originally boxed in with 2x4 and the the slab poured around it. This makes the sides of the hole smooth and vertical. Do I need to drill some rebar into the slab before I fill the hole, or is going to be ok without?

11-02-2008, 08:13 PM
Note: Schluter®-Systems recommends installing the KERDI-SHOWER-ST tray prior to setting KERDIDRAIN whenever possible. This allows greater control over the final position of the drain and makes it easier to obtain full support under the bonding flange.

When KERDI-DRAIN must be set by the
plumber prior to the mortar bed (or when there
is no access to the plumbing from below), the
KERDI-DRAIN is connected to the waste line
and set at the desired height. When installing
KERDI-DRAIN over wood substrates, the
minimum thickness of mortar required at the
perimeter of the bonding flange is 1" .
Before installing the mortar bed, pack loose
mortar under the drain up to the inlet hole to
ensure solid.

so if the overall height of the Kerdi drain is 3 7/8" you need to take off 1" for the required height needed between the flange and the top of slab, then you have the 7/8" where the Kerdi drain slides onto the pipe.
so you need to cut the pipe at 2" below the top of the slab.

11-02-2008, 08:16 PM
Welcome, Peter. :)

I've combined your two threads here. Please bookmark this one and use it for all your project questions so we'll have a history of what you're working on and what's been previously axed and answered. We can change the title to something more generic any time you like.

I wouldn't glue in that riser until I had my tray if I were you. I think the thickness runs in the neighborhood of 5/8ths to 3/4-inch, but I wouldn't bet on it. I don't use the trays and have never actually set the drain for one.

If you must set the riser, make sure it's a little long and you can cut it with an inside cutter when you get your kit.

Who'd you order from that has it back ordered? Might be able to order you one from our friends at Tile ( and get it a bit sooner.

When you patch your slab, though, be sure to allow some room around the riser for the drain. I use a short piece of 4" PVC pipe and remove it once the concrete patch has firmed up enough to support itself. You can use a 4" coupling and leave it in there, but I don't like wastin' them big ol' fittings.

It wouldn't hurt to dowel the sides of your leave-out, but it's not really necessary for that size patch. Do paint a little thinset or Portland on the edges before you pour your patch, though.

My opinion; worth price charged.

Young Brian is fast this evening. :)

Tool Guy - Kg
11-02-2008, 09:40 PM
I second cx's suggestion of giving Tile Experts ( a call. The last order I placed was this past Wednesday afternoon and I got it Saturday morning. :tup2: ...and they have great prices and excellent service.

Tell 'em cx & Bubba sent ya. :)

Peter B
11-02-2008, 11:02 PM
Hi Guys,

thanks for the quick response. Since I live in Canuckistan, I wasn't sure tile experts would do me any good, but it turns out that they ship from Canada, and one of their depots is about 20 miles away. Also they are $25 cheaper than Home Depot for the 48" kit. I'm going to call them tomorrow, and if they can get it to me in the next week, I'll wait till it shows up before I cut the drain riser.

Already bought the 4" coupling, cause I thought it would make a nice tidy surround for the stub. Of course no one is ever gonna see it after it's done, but I'll know.

I'll probably dowel the sides of the hole in the slab, if only because it'll be a good excuse to buy a hammer drill.

Wasn't sure about putting 2 different questions in one post so I split em up, but this way is fine 2. I'll let you know how it turned out.

Tool Guy - Kg
11-02-2008, 11:11 PM'll be a good excuse to buy a hammer drill.NICE! :yeah:

11-09-2008, 08:04 PM
Since I live in Canuckistan, I wasn't sure tile experts would do me any good, but it turns out that they ship from Canada,Fearless and noble leader of Tile ( is Canuckistani hisownself, Peter. :)

Peter B
11-09-2008, 08:07 PM
I'm about to repair my hole in my slab. (Yes I bought the hammer drill.) I have my 1/2" rebar holes drilled about 3" into the slab. What do I use to cement the rebar into the holes? I have some modified thinset and I have some sanded topping cement. Would the thinset work or do I need something else?

11-09-2008, 08:13 PM
Yes I bought the hammer drill.Never mind no patch, what'd ya git? :)

You don't need anything in those holes, Peter. If you drilled half-inch holes and are using half-inch re-bar for dowels, the fit should be sufficiently snug. You're not looking for any pull-out resistance here, only stopping the lateral or vertical movement. Just drive your pins and pour your cee-ment.

You can tie some pieces of re-bar to the dowels if you like, but with a little hole to patch it's not gonna buy you much of anything.

My opinion; worth price charged.

Peter B
11-10-2008, 09:47 PM
After just buying the Kerdi kit and the Hansgrohe faucets and showerhead, the bucks are a little tight. Ended up buying an $80 black and decker hammer drill. Drilled my 1/2" holes "ok". Not great, just ok. I really wanted to buy the $600 Bosch rotary hammer, but sometimes ya gotta settle. The blackndecker worked real hard to drill my 4 holes but hey it got the job done. The Bosch I rented to cut the slab for the drain drilled twice as many holes in half the time. It punched holes in 20 year old concrete like it was a block of cheddar cheese. Oh well...

Peter B
11-17-2008, 10:11 PM
My shower kind of goes 18" into an adjoining closet. So, I have 2 full walls, and a half wall, with the 4th side open (where the curb is going to go). I'm going to build a pony wall 3' or maybe 3' 6" high to make up the other half of the half wall. I plan to use the kerdi curb.

Question 1. Some pictures I've seen have a pony wall that ends dead flush with the front of the curb. Some pictures I've seen have a pony wall that goes 2 or 3 inches past the front face of the curb. Is there a right/wrong way to do this or is it just about looks.

Question 2. Will my Glass Guy need to attack anything to the curb? Cause I'm thinking that screws into the kerdi styrofoam curb are not going to work. (Yeah I know, I should just ask the glass guy)

11-17-2008, 10:45 PM
1. Dealer's choice.

2. If he attacks your curb, you attack him right back, Peter. :D

If he wants to attach anything to the curb he should do so with adhesive, not mechanical fasteners. He wants to poke any holes in your curb, you send him home.

We've had folks install frameless glass on those curbs and I've not heard of any problems to date. If the curb is properly installed, you should be able to install whatever you want on it.

My opinion; worth price charged.

Peter B
11-24-2008, 09:48 PM
Easy question, but I'll ask anyway. Shower is going to have the Kerdi tray. I'm going to hang the drywall first and then put in the tray.

Usually when I've done drywall, I leave the bottom edge 1/2" off the floor. I assume I should do the same for my Kerdi shower?

11-24-2008, 10:38 PM
Sure Peter, leave the DW up off the floor some.