Disfavor of sunlight is a typical vampire trait, as is the extreme sensitivity of the eye to any light source. This apparent vampire trait may also serve as an explanation as to why Roderick has by his own admission, not left the house for many years and why "to an anomalous species of terror (the narrator) found him a bounden slave (532)." However, there is an alternative explanation for Roderick's being housebound, the inability of vampires to cross water. On arrival to the house, the narrator describes a "dank tarn" or lake in which he has to pass in order to get to the House of Usher. Therefore, Roderick would have to cross it in order to leave, which as a vampire is an impossible task. Roderick and Madeline physically fit the description of vampires and clearly possess the distinct vampire traits and mannerisms. The physical characteristics of the Ushers help to justify their actions and the extent of this supernatural horror.
While physically hideous, the traditional vampire is also psychologically repugnant. He is evil. He isolates stands outside of, and therefore, threatens normal society. It can be assumed that the narrator, in "The Fall of the House of Usher" represents this "normal society". Roderick and Madeline "isolate" themselves from normal society both physically and psychologically. Neither has left the house in years, and Roderick is afflicted by what he describes as a "family evil". Some of this evil being that the "entire Usher family lay in the direct line of decent (530)." Since he and Madeline are the only Ushers left, and as they are identical to the minutest detail, one can assume she suffers the same affliction. Roderick has summoned the narrator to comfort him because of the "approaching dissolution (532)" of his sister. However, Roderick's true intentions may be much darker, justifying his vampire mentality. Enlisting the help of a childhood friend in burying his still living twin sister is certainly an act of someone who isolates themselves from normal society and is empty of moral code.