The giant house spider has been treated as either one species, under the name Eratigena atrica, or as three species, E. atrica, E. duellica and E. saeva. As of April 2020, the three species view was accepted by the World Spider Catalog. They are among the largest spiders of Central and Northern Europe. They were previously placed in the genus Tegenaria. In 2013, they were moved to the new genus Eratigena as the single species Eratigena atrica. In 2018, the three separate species were restored. The bite of these species does not pose a threat to humans or pets, and they are generally reluctant to bite, preferring instead to hide or escape.
The two sexes do not differ in coloration or markings. Its coloration is mainly dark brown. On its sternum is a lighter marking, with three light spots on each side that form an arrow-like shape pointing toward the head of the spider. The opisthosoma features a lighter middle line with six "spots" on each side. The giant house spider has the same coloration as the domestic house spider, Tegenaria domestica; it has earthy tones of brown and muddy red or yellow. They also have conspicuously hairy legs, palps, and abdomen. The female body-size can reach 18.5 millimeters (0.73 in) in length, with males having a slightly smaller body at around 12 to 15 millimeters (0.47 to 0.59 in) in length. The female leg-span is typically around 45 millimeters (1.8 in). The leg span of the male is highly variable, with spans between 25 and 75 millimeters (0.98 and 2.95 in) being common.
Its eight eyes are of equal size and are arranged in two rows. As the eyes contain fewer than 400 visual cells, E. atrica can probably only distinguish light and dark.
