댁 is the honorific form, so you would use with honorific subjects such as older people/ people of respect.
I know 우리 could also mean "my" and not "our", but "our" should still be accepted. also it marks "house" as wrong and insists it to be "home", although there shouldn't be a difference, as there wasn't in previous times.
I put, "Our grandfather stays at the house." Did I get it wrong because it was not 우리들의?
If I'm speaking to someone who is not my sibling or cousin would I still say "our grandfather?"