Question in a nutshell: What is the most correct way of handling grout at a change of plane in a shower, particularly at inside corners?
I've done some searching in the advice forum and in the Liberry
, but I have only found bits of an answer, not anything comprehensive in one place. I think I've figured it out, but a number of folks have contradicted my answer, including a few local "pros", so I'm asking people I trust.
What I think the answer is:
- General rule: Don't grout in corners. Leave them open and caulk instead.
- Partial exception 1: Outside corners are a lot less sensitive. If you have a stable structure, you might get away with grout here, but it isn't "right".
- Partial exception 2: If your substrate is a contiguous mud box instead of a board product, it may be stable enough to let you use grout in the corners, but this also isn't "right".
The only part of that I'm certain of: "It's industry practice to caulk at any change of plane". As an amateur, that really doesn't tell me enough.
Background story: I have a glass tile shower that I did myself. I was told that glass has extra susceptibility to flexing, so I should pay extra attention to caulk rules. When I grouted, I used a dental tool to rake the grout completely out of the inside corners. After the grout was well cured, I went back and filled the corners with caulk. I grouted the outside corners along the top of the curb on the reasoning that it's a solid mud curb so the grout shouldn't crack, and if it does it'll be because I have much bigger problems. I haven't seen any problems yet, but it hasn't been finished long enough for me to say there won't be.
I've never really been happy with the color mismatch between the caulk and grout, but I've now seen other jobs that didn't have that problem, so I'm wondering if the caulk color was mislabeled and have investigated replacing the caulk. However, when I started looking for a color match, local "experts" started popping out of the woodwork and telling me I'd done it all wrong. Things I've heard:
"You should have put grout in the corners. You only use caulk at joints with dissimilar materials like where tile meets preformed shower pans."
"Grout in the corners is fine if you just put a thin bead of caulk over it. If it does crack, the caulk prevents mildew from growing in the crack."
"You aren't supposed to grout the corners, but everyone does because it's hard not to, and customers complain if you don't. You might get hairline cracks, but it'll hold up fine."
They've generally said I was a fool for raking out the whole corner. Now I doubt what I thought I knew before. On top of that, I'm now planning for a second bathroom, a much more ambitious project, and would really like to know the right answer before I start.
So, what is the proper way of handling shower corners? I'm hoping for a complete answer from the pros that not only helps me, but that we can point later newbies toward as a reference. If you want to add a description of your techniques to make it easier or when you think the rules don't apply, that's wonderful too.
Two obvious follow-on questions:
If outside corners should be caulked, how do you handle outside corner tiles, the kind that wrap around the entire outside corner at least an inch or two along both walls/planes?
Is the answer the same for dry environments such as a tile floor with a few tiled steps, or is it accepted just to grout and live with the cracks since they won't be wet and growing mold?
Thanks to all for putting up with this.