The J. Edgar Hoover Building is in an architectural style known as Brutalism. The term is derived from the French term "béton brut" ("raw concrete"); in Brutalist structures, unprocessed concrete surfaces are commonly used to create "rugged, dramatic surfaces and monumental sculptural forms." The concrete of the Hoover Building shows the marks from the rough wood forms into which the liquid concrete was poured. The exterior is constructed of buff-colored precast and cast-in-place concrete. The intent was to attach sheets of polished concrete or granite to the exterior. The exterior walls were built to accommodate these attachments, but this plan was abandoned as the building neared completion. The windows were of bronze-tinted glass. The cornice line is high on the E Street side. The interior, as built, consisted of white vinyl floor tiles, and polished concrete ceilings and floors painted white. The open-air courtyard was paved with grayish-beige stone, and contained an arcade to shelter employees as they moved around its edge.