Sorry for keeping this "House" topic going but I did some more checking. Nick called their house "my house" at least 5x in S1. I think what adds to the confusion is the whole amnesia arc where Juliette called it "my house" 2x and that was during the S2 amnesia period where she remembered everyone (including Nick's friends) except for Nick himself. And Nick even comments later in one episode and says "it's like I'm a stranger in 'your' house but to me, it's 'our' house". All references of Nick were wiped away so it stands to reason she'd see their house as only her house. It's a lot easier to remember certain details during a horrible storyline compared to similar (yet different) details during inconsequential episodes that preceeded the amnesia plot.
There are a ton of references to "Nick's house" or a variation of it from the scoobies and other characters compared to similar references to "Juliette's house" or a variation of it and that's more to do with Nick being the main character who had all the crap constantly happening in "his" house.
There are a ton of references to "Nick's house" or a variation of it from the scoobies and other characters compared to similar references to "Juliette's house" or a variation of it and that's more to do with Nick being the main character who had all the crap constantly happening in "his" house.