I don't think you are to seal grout in a shower, it needs to breath. The applied waterproofing over the cement board will protect your wall assembly as long as it was applied as directed to the proper depth of product. I wouldn't try to grind a grout space either. You risk the chance of damaging your layer of sealant. I hope a pro checks this and comments.

You just described a complete do over. Or a wait until the other shoe drops and you start having major issues.

https://www.ceramictilefoundation.org/homeowners-guide-to-hiring-qualified-tile-installer

What are these major issues you're speaking of?

We bought the water sealant and mastic as recommended by the person at Lowe's. What problems will arise with this application?

We don't really care if it looks off and the goal isn't a perfect shower at this point - I just don't want mold problems, etc. because of the tiny areas that unhanded grout won't really get into.

And frankly, if the worst I'm looking at is a small chance of some tiles not holding, then that's better in my head to redo those tiles at that time than to rip it all out and redo it now. I know that seems lazy, but it's more because of time and money and I'm just being realistic. This is a bombshell after what has been a lot of work.

Did you use “mastic” or “tile setting morter”.? I believe it is a tear out if you used mastic. Mastic is not for wet locations. You will have failure with typical mastic.

Another forum that is full of professionals is the John Bridge forum. Check that out too.

Mastic=mold. No place for grout=tiles falling off. Incorrectly built pan=major leaks. No mil gauge=not to any industry standard.

Lowe’s=Complete redo.

Get one one of these. https://www.tcnatile.com/products-and-services/publications/218-english-publications/188-handbook.html

But it will be far easier to just hire the Pro to do it right than it will to take the months that time to learn how to do the job correctly. And then more months to practice.

You could remove the ones that are touching and install them again, the picture you posted shows that it can be done; if there's no grout in between them there's risk of water leaking trough the gaps.

@Creative Tile CT, Thanks for helping Garrett.

Wow. So many who just say rip it out and do it again, without any kind of reasoning or possible remediation! I guess i HAVE been gone for a while!!

Well, I'm no expert in anything...bit I would go ahead and dig out the mastic where needed and then grout it.

Then see how it does...I know not the "correct" way to do it...but I'm an optimist.

However, my bathrooms are on a slab so I wouldn't have a ceiling falling on me.

As far as looks go, tile doesn't look too great until it's grouted. We use epoxy grout...

It’s mastic. It re-emulsifies. I stand by “rip it out” sooner or later. Choosing Later only makes the mold worse then.

"I guess i HAVE been gone for a while! "

@ BIll you must have been gone when the OP stated he used mastic. Oh buddy, after what 58 years in the trade, but hey you got 5 likes out of the deal so there is that :):)

I know no other way to reason then to tell OP to tear it out now and bite the bullet even if thats NOT PC here on hooz.

from OP:

"We bought the water sealant and mastic as recommended by the person at Lowe's. What problems will arise with this application? "

"I just don't want mold problems"

Yeah, I missed that. This was not the only thread I saw people recommending everything be ripped out, and THAT was the reason for my comment.

Its gotten a bit rougher around here ill admit that young man. Cracks me up the reasons in which people the hit like button though

All kinds of people trying to get their company name out there. :-) They need to realize, though, if all they know is rip it out, no one's going to listen to them after a while. You and Greendesigns DO have a good point here. But the other one I saw, wow. If you're going to tell someone they need to trash several thousand dollars of work with little chance of recouping their money, you better have a damn good reason, and be ready to back it up with fact.

I hit that like button!

In tiling a wall or floor is it necessary for there to be grout in gaps or can al the tiles be laid touching with no gaps

The tile needs to grout and needs to NOT be touching.