Niche Layout & Waterproofing

[K10BOLTS]

Hello,

I am in the process of laying out a niche in the back wall of a tub surround using 12" tile. I already have poly behind the CBU overhanging the tub flange and will be waterproofing the niche with RedGard.

In an attempt to line up the vertical joints using full field tiles on the back wall, I do not have room to apply 1/2" or 1/4" CBU to one of the wall studs to form one of the niche sides. In other words, I measure 11-3/4" from the left wall to the edge of the stud where the niche will begin. Is it acceptable to skim coat one of the existing wall studs with thinset and apply RedGard over the thinset? My gut feeling is that the answer is NO!!?? If not, I will adjust my layout.

Thanks,
Matt

[jadnashua]

Thinset and dimensional lumber do not get along, so no, you cannot apply the cbu to it reliably.

[Houston Remodeler]

Matt,

Some pictures may help us come up with ideas as how to make this happen.

Normally I cut in our niches after tiling has started so the grout lines are perfectly aligned.

[K10BOLTS]

Paul,

I am on board with running your field tiles up to the niche to finalize your measurements. My goal is to align the horizontal and vertical grout lines of the niche with the field tiles. If you look at the picture I will essentially be starting the left side of the niche against one of the existing wall studs. The red snap lines indicate the rough CL of the wall studs and the tile with tape indicates the niche which will be 2 tiles high.

I pulled more measurements when I got home tonight and have determined that I can indeed attach 1/4" backer board to the stud on the left side of the niche. However, this only allows me 1/8" of fudge room before the tile jogs away from the left wall, or the vertical grout joint gets pinched. This was measured from the tile tile butted against the left wall.

I have verified that this left wall is within 1/8" from top to bottom. This was determined by shooting a laser along the back wall and measuring off of that.

What are your recommendations?

1. Should I run with this?
2. Don't risk it, adjust the layout on the back wall and sacrifice the vertical grout joints lining up.

Thanks,
Matt

[K10BOLTS]

Guys,

I have the niche cut out and am ready to place CBU around the inside. I have a question about the waterproofing before I mix any thinset.

I had initially planned on using RedGard but I just purchased a roll of Kerdi for my other shower project. Being that I already have poly behind the CBU would you recommend that I stick with the RedGard, or use some of the Kerdi to waterproof the niche and extend it out a few inches around the flange?

[Bodie Powers]

Matt, drywall is not an approved substrate for Redguard...you'd need to put some 1/4" CBU in the niche back, or use Kerdi.

[mullet]

Can you put Kerdi directly to wood?

I worry if he Kerdi's the back of the niche and then later someone removes the drywall from the other side of the wall it will rip the kerdi with it.

[Bodie Powers]

Originally Posted by Matt

I have the niche cut out and am ready to place CBU around the inside.

Chuck, he's gonna attach CBU to the niche sides.

[K10BOLTS]

Sorry for the confusion, I will be applying CBU to the sides and back. This is just a work in progress picture. There will be no drywall exposed.

My question was whether or not to continue with a liquid membrane, or use Kerdi to waterproof the niche and extend it out a few inches. As I mentioned, I already have poly behind the walls.

[Bodie Powers]

Either way would work, Matt. If you choose Redguard you'll want to set reinforcing fabric at every change in plane, embedded in the wet pink stuff. If you Kerdi, then yes run it out onto the wall a few inches.