Since my last posting, I've discovered potentially bigger problems. Any advice on how to deal with these? Just fill? It seems that the previous owner took out the sliding doors and installed windows, creating a book in the room. That part off the floor is 1/2 inch lower than the main master bedroom.
Concrete – Cracks on second store concrete slab…bigger
concreteslab
Best Answer
Having established in your prior question that this "slab" is merely a cosmetic/acoustic treatment (or "topping slab" as another poster called it) over whatever structural floor is holding it up, just fill the gaps up. If vaguely level, some sort of floor leveling compound (which may be what the "slab" is anyway - "gypsum cement" or gypcrete rather than concrete) should work.
Otherwise (if not level) you might want a less fluid product to fill it with that will stay put where you trowel it.
Think of it as having (more or less) a plastered floor, as that's closer to what it appears to be than "concrete." So you just need to patch the "plaster" until it's a level surface.