Follow up - Kerdi curb over tile [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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07-18-2019, 07:46 PM
Hello. The folks on this forum helped me do a Kerdi shower from the ground up several years ago. It worked out great. Forgive the follow up to a reeeeally old question, but it's the same topic as the previous post, just additional detail. I have a similar issue. I'm re-tiling a shower - taking out the old tile & wonder board (or whatever is under the tile) and using Kerdi right on the drywall. I'm using the Kerdi shower bed & drain as well. I'm moving the shower curb outward about 4" (see picture). As with the previous question, this will place the curb over existing tile. I plan on using Kerdi all the way to and over the curb right down to the tile floor (I may just use the Kerdi curb with the embedded membrane so I just have to seal the edges). I realize by doing it this way I won't have a water-tight edge where the outer edge of the curb meets the floor (though I plan on using a silicone bead there). The existing tile is on Ditra, so there will be a very slim chance the water can get anywhere even if a little makes it past the silicone.

Question - how do I set the curb on the tile? I understand I would use unmodified thinset where the curb meets the walls, but what about the base? Would it be best to use thinset there, or a waterproof construction adhesive. It seems to me the latter would have better adhesion and a better chance of keeping out water?? Since the problem area for making things water tight is in rather than outside the shower, perhaps I'm worrying unnecessarily. Thanks.

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07-18-2019, 09:41 PM
Outside of the shower isn't considered a wet area, so, with Kerdi over the top and down to the floor, there's no big reason to waterproof either under or outside of the curb. I would not use construction adhesive...use the wrong stuff, and you might melt the foam! I'd probably use a good modified thinset to bond it to the existing tile. As long as it isn't a latex modified thinset, it will probably work. Since you wouldn't be using it elsewhere in a Kerdi shower, you might want to just use some KerdiFix to bond it in place versus a modified thinset. I'd probably call Schluter to get their take on this, though.

07-18-2019, 09:48 PM
Welcome back, Barry. I've separated your post from that old thread to prevent confusion on both.

07-19-2019, 10:08 AM
Awesome. Thanks guys.

07-19-2019, 02:20 PM
One more since you are the masters of time, space and dimension re: all things kerdi. :) For the adjacent tub, which will remain the same except for new tile around the back and bottom, I understand that the portion inside the shower walls and the intersecting ledge will require kerdi, but are the other areas considered wet areas, and do I need to take any special measures in mounting the tile there - i.e., is kerdi necessary or advisable? The tub has no shower and it's actually used quite rarely.

07-19-2019, 02:36 PM
In a soaking tub without a shower, Kerdi on the walls and deck surface is maybe more than technically needed, but not a bad choice since you could be splashing some water up on the deck.

IN a bathroom, outside of the shower is considered a dry area. If the ceiling is 8' or more, it, technically it isn't a wet area, and you don't even need a special lamp if there's one installed there. Still, not a bad idea, though. In a shower, you want the water management to go up at least as high as the showerhead...more is nice, but not required.

Some people want to treat the whole bathroom as a wet area, and that's okay. Then, you'd want the waterproofing to go up the wall some all the way around, but the doorway and the toilet seal can be problematic. In that case, a wall mounted toilet is much easier to waterproof the floor with.

07-19-2019, 05:48 PM
Gotcha. Thanks again.