How is the narrator's first impression of the house confirmed throughout the story in the fall of the house of usher

In the opening paragraph, the Narrator is describing his arrival on horseback at Roderick Usher's isolated abode one dreary evening. He immediately feels an irrational fear upon viewing the huge, decrepit house. Among the mansion's singular features are windows which resemble eyes and a fissure in the stone zig-zagging its way through the facade.
We learn that the Narrator and Usher were childhood friends. Recently, the Narrator received a letter from Usher. In the letter, Roderick described a certain "mental disorder" that was plaguing him, and he communicated a desperate desire to see his old companion. The narrator continues to see this disintegration both of the house and Roderick throughout the story until the final collapse.