Glue up or direct to stud - waterproofing seams?

[Andy911]

Hi, I'm planning to use wall panels for my 48" x 36" corner shower because I like the clean look of a single white panel matched with a white shower pan, as well as the lower maintenance. However, I am a little concerned about how to properly waterproof the wall-wall corner seam?

For the direct to stud kits I have seen, they all have some hardware to connect the panels together but they all still seem to rely primarily on a bead of silicone to waterproof this seam and I am deeply skeptical this will hold up over time. Am I being too paranoid?

For a glue up kit it seems to me that the opportunity is there to use a waterproofing membrane behind the panels. If I used Kerdi I am concerned that the adhesive for the walls would properly bond to it, but I was thinking something like Redguard would work well? Note in this case its really just to waterproof the corner so it probably doesn't need to applied behind the entire walls, but if I was going to do it I probably would just in case

Appreciate any thoughts on how you think this should best be done would be greatly appreciated.

Thanks!

 

[Jbrk]

Waterproof the walls, while you have the shower out. Redundancy is important for water issues like this.

Either kerdi or redguard is fine. I'm partial to liquid applied membranes like redguard, mostly because I hate tiling and kerdi requires trowelling on mortar for the adhesion. But it still works.

Make sure you have a path for water to go at this waterproofing layer, meaning should your primary barrier (the silicone seals at the joints) give up overtime, the water that gets past it is going towards the drain and accumulating and rotting the floor under the shower pan.

 

[Sponsor]

 

[Jadnashua]

Having two waterproof layers on top of each other can lead to a constantly wet surface since if there's a defect or error in installation, if any moisture DOES get in between, there's no easy path for it to evaporate or drain.

Personally, I'd follow the manufacturer's instructions.

FWIW, even mortar (thinset) doesn't actually 'stick' to Kerdi. It bonds things because, when things are properly installed, the adhesive flows around the fleece, then cures, locking it in place.

 

[Andy911]

Thanks both. Sounds like a middle ground solution may be to use some waterproofing just at the corner (plus 6-12” per side) and make sure it laps over the shower pan flange at the bottom?

I have a similar question in case I install a niche (one of the products comes with niche options installed on site). Build a waterproof backer box?

Thanks!

 

[Jadnashua]

Without knowing the materials used, and how the niche is constructed, it's nearly impossible to advise.

Niches can be troublesome, as there's a lot of joints, and thus, opportunities for leaks. Some preformed niches are essentially already water tight, and your main issue then becomes how to properly bond it to the rest of the wall. If you're going to build it yourself, the bottom and any shelves should have some slope out into the shower so water doesn't pool there. Also, cement board is NOT waterproof, but is not damaged by being wetted. Neither are tile or grout, which are considered decorative, wear surfaces in the industry. So, depending on what the niche is made of, you probably will need to apply some waterproofing to it, and that could be a liquid applied material like say RedGard, or a sheet membrane, but both of them would be problematic sealing to an untiled wall covering as the niche's waterproofing would need to overlap the edges of that.

If the niche is essentially prefinished, you may only need to cut a hole, then seal it in place with say silicon. Hard to say without knowing what you actually have or plan.

 

[Andy911]

Thanks. It would definitely be a pre-finished niche. For example the niche in this picture is end user installed into the flat walls by cutting an opening and siliconing it:

http://vanico-maronyx.com/Shower/Selection/Planix-137

The manufacturer instructions are just to glue it but I do have the same long term concerns that this bond will eventually weaken and fail?

 

[Jadnashua]

Silicone, can fail for a couple of reasons:
- the two surfaces move beyond the elastic limits, tearing it away from one surface
- the surface(s) were not clean before installing

I suppose there are some chemicals (maybe in cleaning) that might degrade the structure. But, in reality, the stuff is pretty robust.

There are other sealants that could be used. Something like KerdiFix is a silane based product that is very robust and sticks to almost anything. Not as flexible as most silicones but harder and a stronger bond.

 

[Andy911]

Okay thanks, makes sense. I think I have a plan now

Cheers

 

[Andy911]

Would Kerdi-Fix be a good product to use to glue up the shower walls with? (particularly if I’m using something like Kerdi band behind the walls at the corner)

 

[Jadnashua]

KerdiFix is not inexpensive, but yes, you could use it if you wished. Depending on what you are trying to bond, the shear strength can be upwards of 1400 psi, overkill for many things. But, the stuff is very stable, has zero VOCs. It cures slowly, only about 1/8" per day, but tacks well, but you want to support it until things are locked where you want them, since you'll not move it later! Kerdifix over Kerdi, the limiting factor tends to be the fleece, which is only required to have a minimum of a 50 psi shear strength...it typically tests out to greater than 75, but much less than a solid surface - the fleece will tear off the main membrane body.

I'm standing on a 2" piece of Kerdiboard that was glued in place with KerdiFix. It sat overnight. This was at a Schluter workshop. The thing would have needed at least another week to reach full strength, but after maybe 15 hours, it's holding me up (230# or so).