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kdawg89 01-15-2020 05:39 PM

Rebuilding a shower with Kerdi
Hi All,

I am rebuilding a shower and just need a little advice. I am using Kerdi board for the walls, the pan and curb are TBD how I am building them.

One side of my shower is a tub deck and the glass will sit about an inch from the edge of the tile, one of the issues I had with the shower originally is the tub deck actually slopes slightly away from the drain so water would get through. I am planning on using Kerdi board under the glass and in order to get the slope going the right direction using a little thinset to build a little slope on top of the plywood tub deck and then setting the Kerdi board on top of that. Is that a good idea?

On the pan the area is 40X59, so the 38x60 Kerdi tray is just a hair off, I am thinking to trim a half inch off the tray for the long dimension and use dry pack mortar to extend it slightly on the short dimension, is that a good idea or will it cause the elevation of the tile to be noticeably different?

Lastly on the curb it will be on a wooden subfloor, I was thinking of using the Kerdi curb but my tiles are 4x16 and the Kerdi curb is 4.5 inches wide so it isn't a great match in that aspect. So then I thought maybe I would build it out of Kerdi Board, I am not entirely sure how to do that but is that a decent option? The other thing is the shower glass places I have called all want to anchor to the curb to prevent side to side movement, that is also one of the places my last shower leaked so I am not real excited about that. If they drill into my Kerdi board curb can I just jam the hole full of Kerdi fix before they put their screw in?

Thanks in advance!

cx 01-15-2020 06:35 PM

Welcome, Kelly. :)

1. Probably not. How would you deal with the remainder of the tub deck if you have a raised ridge at the shower end? The tub deck is also to be tiled?

2. That is a method recommended by the foam tray manufacturer. I prefer you don't use the foam tray at all so I'll let others comment on that. Is the drain centered in the shower footprint?

3. Probably easier to build a wood curb and just cover it with some of your KerdiBoard, but you can do the whole thing in KerdiBoard if you want. Many people do and have done.

Regardless how you construct the curb, I would not let the glass installers drill through the waterproofing membrane on the curb or any other horizontal surface in the shower for any reason. They do not need to do that and it's time they learned that.

My opinion; worth price charged.

kdawg89 01-15-2020 06:49 PM

Thanks for the input. I should be more specific on the tub.

The whole tub deck will be tiled so I would use kerdi board under where the glass will be, and then just 1/2in Densshield for the rest of the tub deck. I should be able to make up for the height difference where there is thin set under the kerdi board with the thin set on the top of the densshield.

You think I am better off just building a mud pan and using a Kerdi drain? Then do you put Kerdi membrane on top of the mortar? So something like tar paper, mortar, Kerdi membrane, tile?

So use wood to build up the curb and then cover with Kerdi board, what is the best way to slope the top of the curb into the shower?

Should they just silicone the glass to the tile and anchor it on the walls? Where they anchor into the walls should you put kerdi fix in the holes before the put the screws in?

cx 01-15-2020 07:00 PM

1. Good luck with that.

2. I do, but that's up to you. Over a wood framed subfloor, it would be roofing felt (or similar), 2.5 lb. metal lath, mortar, membrane, and tile.

3. If you have KerdiBoard on hand, yes. You can also clad the wood curb with drywall, CBU, or some of your DensShield.

You can rip the top board for slope, use thin wedges on the outside between the top board and the one below, or similar. We're talking only 1/8th" or less here.

4. Number of ways to do it, generally involving an epoxy adhesive, but I've heard of it being done entirely with silicone. Depends upon the application and the hardware they use.

They will not have heard of KerdiFix, but generally on vertical surfaces it's considered acceptable to use 100 percent silicone in the fastener holes before installing.

My opinion; worth price charged.

kdawg89 01-15-2020 10:26 PM

How would you recommend handling the slope on the tub deck if not by putting a little thin set under the kerdi board?

cx 01-15-2020 11:13 PM

I would want to make the tub deck slope toward the shower drain, Kelly. How? Dunno, can't see it from here.

You can use the paper-clip icon above the Reply dialog box to attach photos from storage on your computer.

ss3964spd 01-16-2020 08:49 AM

If they insist on installing a bracket on the curb, Kelly, allow them to drill only as deep as the tile is thick, say 3/8". Then have them cut the SS bracket mounting screw to 3/8". In preparation for this you'll have already made a Depot or Lowes or Menards run and picked up some JB weld clear epoxy, the one with the little nozzle that mixes parts A and B as they are dispensed. Squirt that into and fill the hole, poke at it a bit to make sure no air is trapped, set the bracket and insert the screw. Let it set up for as long as you can make the installers wait.

kdawg89 01-16-2020 10:39 AM

1 Attachment(s)
Here is a photo of the tub deck. Would it be best to cut the OSB where the glass goes and unscrew it and then shim it somehow to create a slope?

cx 01-16-2020 11:57 AM

In that application you could cut a strip of the OSB as you suggest and bevel the framing under that portion a bit to provide the slope. Or you can probably just use a belt sander or similar to bevel the OSB to provide the slope. Keep in mind that you'll need to provide a break in your tile surface at that pitch change and if you still plan to put a foam board on the tub deck, you'll need to break the foam board at the pitch change as well.

You just need to do whatever is required to ensure that the waterproofing layer on the horizontal portion that remains within the shower area is properly sloped to drain. And the tile on top of that portion, too. But you still need to provide a flat surface on the remainder of the tub deck for your tile installation there.

Were I doing it the tile would be separated at that pitch break and the fixed glass would be installed in the gap in the tile on top of the waterproofing layer captured in place by the tile installation.

My opinion; worth price charged.

kdawg89 01-18-2020 11:43 AM

So it turns out I have 1 pair of studs that are 22 inches on center and Schluter says for 1/2 kerdi board 16 inch on center is the max spacing. Adding a stud for the height of the shower will be tough because it has blown in insulation. I am thinking to possibly use Densshield for that section of the wall and then using Kerdi membrane and joining to the the Kerdi board. Do you think that is my best option? The main reason for densshield is I already have several sheets left over from when they built the house.

EDIT: The other thing I can do it built it up to about 1/4 below flush with the existing studs, if I do that can I wet shim the last 1/4 inch?

cx 01-18-2020 12:53 PM

Kelly, have you checked the manufacturer's requirements for stud spacing for use of that product in wet areas?

I'd suggest you fix your framing.

My opinion; worth price charged.

kdawg89 01-18-2020 01:31 PM

1 Attachment(s)
I worked out how to fix the framing where the studs were spaced too far. Another issue I have with the framing is in one of the corners. The kerdi board in one direction doesn’t have stud to attach too. Is that how corners normally work is or the wall built wrong? I can’t find anything from schluter how this particular issue. Can the “floating” sheet of kerdi board butt up to the anchored piece with a little thin set and then put kerdi band over it like normal. Or does there have to be a stud there to anchor it to?

cx 01-18-2020 01:52 PM


Originally Posted by CX, Post 11
I'd suggest you fix your framing.

Kelly, you can do whatever you like in your shower, but I'd recommend you read and follow the manufacturer's instructions for each of the products you intend to use.

Having an unsupported edger of your KerdiBoard would not seem to me to comply with their recommendation of a maxim of 16" on center stud framing. That customarily presumes fastening to the framing members. But you might read that differently.

My opinion; worth price charged.

Carbidetooth 01-19-2020 10:55 AM

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The way your corner is framed is not wrong...just different. That type of corner was conceived to save both material and provide a better insulated corner with less thermal bridging.

Were it me, I'd take a stick of 1x4 and attach to the backwall stud with screws driven through the stud. Drill pilots through stud so screw pulls on 1x4, not the stud itself. Could also be done with 2x material, but compromises the insulation a bit more.

kdawg89 01-25-2020 09:11 PM

Thanks for the info so far!

I have overcome all of the previous mentioned framing issues, and now the Kerdi board is up. Have a couple more questions for situations I don’t know how to handle.

I have a vertical seam where the Kerdi board meets drywall, this is well outside the wet area, in fact it is too far outside the wet area due to being the next available stud outside the shower area. I would like to paint about 6-8 inches of the kerdi board, should I just mud and tape it like drywall or Kerdi band it? Then would I just skim the Kerdi with joint compound and then prime and paint it? Ultimately then I would tile over and overlap the painted area just a bit with tile.

The second question is I have a horizontal seam up above the wet area where Kerdi meets drywall. I think on this one I could tile over the seam, the problem is that drywall has about 1/8 of an inch of drywall texture so there is an elevation change problem where the Kerdi meets the drywall. Wondering if anyone knows the best way to handle that situation. Maybe it is a none issue because I am using 1/4 x 1/4 inch square notch trowel (tile is 4x16 subway tile) which should leave me with 1/8 in of thin set so maybe the transition will work itself out?

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