Drywall mud can be used to skim coat concrete, it’s done fairly regularly in commercial construction.

Also, I don’t know how old your condo is, but it never hurts to test for asbestos.

Quarry tile comes in everything from a dull white to a deep red in sizes from 4x4 up to 12x12. It is used everywhere from commercial kitchens to K12 educational environments to commercial automotive shops. I have dealt with literal tons of quarry tile in schools and homes built in the 1950’s to the early 2000’s and can confidently tell you it isn’t limited to red 6x6 tiles.

Just because you sell tile and have attended a handful of TCNA courses doesn’t make your knowledge the end-all, be-all. We’ll agree to disagree on this one.

What the hell are you talking about?

1. tile is absolutely laid on thinset with a notched trowel. The qualifiers “with” or “on” make zero difference in OP’s situation

2. I never once stated it was unacceptable to lay tile on a concrete substrate

3. This is absolutely quarry tile. I have either personally installed or overseen the install of this exact quarry tile nearly a dozen times in my two decade’s long career in various residential and commercial construction settings

4. I asked if OP had clearer photos to adequately address the situation. Where you’re coming up with these wild generalizations is beyond me

Lexan and epoxy? What exactly are you trying to do?

Cement board is more than sufficient. The other options are nice and a lot easier to work with, but are also a lot more expensive. I’ve been in some form of residential or commercial construction for nearly two decades and 95% of the tile jobs in bathrooms had cement board behind them. Make sure your tile guy tapes the seams with fiber mesh and floats the joints with thinset and you won’t have any issues.

Tile isn’t laid on grout, it’s laid on thinset mortar. This is called quarry tile. Can you get better photos of the grout you’re dealing with?

Some traps are intended to be glued. Sounds like OP’s is a screw together kit that doesn’t need anything but the included ring seals.

No. The only tankless toilets that vary from typical flanges are wall hung (carrier) toilets which aren’t all that common in residential settings. OP needs to ensure he has the water pressure for the tankless unit to operate in the first place.

He isn’t talking about the toilet flange. Look at his reply.

Even still.. wall studs don’t impact toilet location.

What do wall studs have to do with toilet positioning

Knockdown hides less than perfect finishing & is extremely common in tract/spec homes. Your best options are either skim coating the entire ceiling, or laminating with 1/4” rock. I would choose option #2.

The only truly correct way to repair would to be skim coated in its entirety. A good finisher can skim coat and finish sand both walls in half the time a DIYer could individually fill 1000+ holes and spot sand every one. Plus, the end result will look a thousand times better.

I’ve worked with a lot of finishers over my years in commercial construction and it truly is an art form.

Nope. Need a sewage pump with a turd grinder.

As stated, grout isn’t the solution here. Caulk is the answer.

The install instructions in the link he posted call for 1/2”. Take the old quarter round up then and install something larger.

Quarter round. The install instructions indicate a 1/2” expansion gap is required anyway.

Edit: really any trim profile would work, you don’t have to be limited to quarter round.

Seal the concrete if you’re worried about it. I’d be more concerned about water damage to the bottom plate of your partition walls than I would with the concrete.

Pretty screwed. Definitely going to want to rip it out and redo if you expect any longevity.

Tear it out & replace or tile over it. It’ll never look correct if you paint over thinset.

Yeah, I’ve run across a good amount in my commercial construction career around the Midwest. Funnily enough I just ran into some in my own bathroom remodel this past weekend.

I don’t know which side of the wall you’re drilling on, but you’re likely running into the cement tile board and thinset layer. If it’s on the other (hardwood) side of the wall, it could be self leveling compound.

What is the floor up above? Almost looks like tile backer and thinset

Let the cat inside.

It’s typically even less likely to be load bearing in a basement to be honest. Most finished basements are furred out from the foundation with partition walls going up to the bottom of the floor joists