Freaking Out! Grout lines darkening - Tile Advice

[doofus]

I thought I did everything right--my 13 inch tiles came down and stopped 1/8" away from the tray, I filled it in with mad adhesive, and sealed the grout 3x. Then I noticed, after a few showers, One dark grout line. You can see it in the bottom right of the pic. So I dug it out, and yes, there was moisture back in there. I dried it out and regrouted that area, resealed it 3x. Now, two showers later, almost all the grout lines coming up from the pan have a little darkening going on, like 1/2". What did I do wrong, and what do I do Now??? AAAAAAAAAAAAA!!!!!!!!!!!!!

 

[doofus]

Thanks to everyone for your non-existent suggestions.

 

[bsc ceramics]

Way to go to get advice.. now what adhesive did you use?

 

[doofus]

I used Schluter Kerdi Fix Sealing and bonding compound. Thanks for responding. SInce the post I have pulled this out, however, and discovered more moisture. After it dried out, re-did it with pure silicone, trying hard to completely fill that void under the tiles and the pan. There was no insulation in this interior wall. Worried that was the mistake. Thoughts?

 

[bsc ceramics]

could be, did you tank the shower area 1st?

 

[doofus]

I used cement board sealed with Hydro-Ban. There's a layer of plastic film as well.

 

[parkerfresh]

I’d really like to find out how this happened as it seems quite strange? Normally you’d expect all of the grout to darken as it’s not waterproof, but water resistant, but as you sealed it multiple times, this shouldn’t be the case.

Without being there to see it, it’s hard to tell, somehow water is getting behind the tray to the bottom of the tile where the grout is not sealed, then maybe a capillary action is pulling water up the joint? I’ve not seen this before so hopefully someone comes along with a solution

 

[doofus]

Thanks for writing. This is a weird, modernist building (Ulrich Franzen-designed) and so, interior walls, which are cinder-block, can be cold spaces. I wish I thought about that before. Of course it wasn't 20 below zero when I built this thing. I suspect there was just enough airspace behind the bottom lip of the tile to generate condensation which wets the grout from behind. Well, I filled it up with silicone and someone is about to take a shower, so we'll see if eliminated that airspace. If it doesn't work, I'll be googling "diy blow-in insulation."