Q. Should the names of houses be italicized as you would the name of a boat? What about if someone names their car?
A. A house, no. A car, maybe. For example, you wouldn’t use italics to refer to the White House or Graceland or Big Pink (the names of houses located respectively in Washington, DC; Memphis, TN; and West Saugerties, NY). But that last name, unlike the first two, is not all that well known, so quotation marks might be helpful for the first mention:
Several of the album’s songs were composed at “Big Pink,” the house in West Saugerties. . . . Before returning to Big Pink . . .
In general, however, the rule is simple: the names of houses, like other place-names, are capitalized but not italicized.
On the other hand, if you name your Subaru or Ford something other than Forester or F-150 (see CMOS 8.117), you could pretend it’s a boat and use italics à la Enterprise, a name shared by various military vessels and a series of fictional Star Trek spaceships (see CMOS 8.116). But those are official. Your pet name for your car is unlikely to merit such treatment except jokingly:
Cecil, my prized Celica, is in the shop.
Sorry to hear about Cecil. May he feel better soon.