The Low German house or Fachhallenhaus is a type of timber-framed farmhouse found in Northern Germany and the Netherlands, which combines living quarters, byre and barn under one roof. It is built as a large hall with bays on the sides for livestock and storage and with the living accommodation at one end. The Low German house appeared during the 13th to 15th centuries and was referred to as the Low Saxon house (Niedersachsenhaus) in early research works. Until its decline in the 19th century, this rural, agricultural farmhouse style was widely distributed through the North German Plain, all the way from the Lower Rhine to Mecklenburg. Even today, the Fachhallenhaus still characterises the appearance of many north German villages.
The German name Fachhallenhaus is a regional variation of the term Hallenhaus ("hall house", sometimes qualified as the "Low Saxon hall house"). In the academic definition of this type of house the word Fach does not refer to the Fachwerk or "timber-framing" of the walls, but to the large Gefach or "bay" between two pairs of the wooden posts (Ständer) supporting the ceiling of the hall and the roof which are spaced about 2.5 metres (8.2 ft) apart. This was also used as a measure of house size: the smallest only had 2 bays, the largest, with 10 bays, were about 25 metres (82 ft) long. The term Halle ("hall") refers to the large open threshing area or Diele (also Deele or Deel) formed by two rows of posts. The prefix Niederdeutsch ("Low German") refers to the region in which they were found mainly found. Because almost all timber-framed and hall-type farmhouses were divided into so-called Fache (bays), the prefix Fach appears superfluous.
The academic name for this type of house comes from the German words "Fach" (bay), describing the space (up to 2.5 metres (8.2 ft)) between trusses made of two rafters fixed to a tie beam and connected to two posts with braces and "Halle", meaning something like hall as in a hall house. The walls were usually timber-framed, made of posts and rails; the panels (Gefache) in between are filled with wattle and daub or bricks. One bay may be two or rarely three Gefache wide.