"These architects work at home."
Translation:Ci architekci pracują w domu.
Nope, you almost only use "u" with people. The only other thing that comes to my mind is "u drzwi" (at the door). But that's not common anyway, I think.
Sorry, I guess I am still confused. An earlier lesson was "Jestem u babci" translated "I am at grandma's" (with "house" being implied). So you are saying that if I changed that sentence to "I am at the house" (leaving out "grandma's") it becomes "Jestem w domu" and the only reason "u" was used in the first example is because it said "grandma's"? And, if I wanted to say I am at grandma's house (not just implying house), I would still use "u" in that construction because I am going to a person's place (grandma's house)? Thanks for your previous quick reply by the way.
You're close. But "u" just stays with the person.
You say "Jestem u babci" and that usually means that you're in the place where grandma lives (but if your grandma is in the hospital, that would mean you're visiting her, although she doesn't live there).
If you want to say "I am [in/at] the house", that's simply "Jestem w domu".
If you want to say "I am [in/at] grandma's house" and use the noun 'house' explicitly, then you're still simply 'in the house', doesn't matter whose. That's still "w". "Jestem w domu babci".