The narrator
The narrator is a woman who doesn't leave her house and only looks out her window at the rotting world. After her mother dies she begins to merge with the house and is unable to escape.
The mother
The mother is a passive character of the story. She is described as religious and believing that her prayers are what's saving their home. She later emerges in the narrator's memories or "rooms".
The house
The house is an entity in itself. It prevents the narrator from leaving and suffocates her until she becomes a part of the house.