An outbuilding, sometimes called an accessory building or a dependency, is a building that is part of a residential or agricultural complex but detached from the main sleeping and eating areas. Outbuildings are generally used for some practical purpose, rather than decoration or purely for leisure (such as a pool house or a tree house), although luxury greenhouses such as orangeries or ferneries may also be considered outbuildings. This article is limited to buildings that would typically serve one property, separate from community-scale structures such as gristmills, water towers, fire towers, or parish granaries. Outbuildings are typically detached from the main structure, so places like wine cellars, root cellars and cheese caves may or may not be termed outbuildings depending on their placement. A buttery, on the other hand, is never an outbuilding because by definition is it is integrated into the main structure.
Separating these work spaces from the main home "removed heat, obnoxious odors, and offending vermin" and decreased the risk of house fires and food-borne illnesses. The study of historical outbuildings also offers information about the lives of workers otherwise excluded from the history of a place, since one possible purpose of an outbuilding was to reinforce class boundaries.