Used as a noun, often with particles like が, を, に, の. Emphasizes individual houses one by one.
Flowers were displayed at each and every house.
He carefully inspected each house.
house to house; door to door
Used adverbially, often with verbs like 回る, 訪ねる, 配る. Describes going from one house to the next.
I delivered newspapers from house to house.
The police are making door-to-door inquiries.