Nagaya (long house) (長屋)

Nagaya is a style of collective housing.

It is a building in which two or more dwelling units are situated horizontally, having walls shared with those of the adjacent units. Alternatively, it's a building divided horizontally into a number of areas, with each such area being used as a dwelling unit. An entrance is provided for each of the dwelling units.

An essential condition for a nagaya is that the entrance to each dwelling unit must connect directly to an external path, and this entrance must not be shared with those to the other dwelling units.

Recently, it is often called a terrace house.

Semi-detached houses are often seen in Europe, such as in England. A building (generally of two-story configuration) is divided into two parts at the midpoint, and one of the walls of each of the two parts, as in a row house, is shared by adjoining dwellings, thus economizing on land usage and the cost of construction. It is also thought of as a building that comprises two houses.
(An independently built house is called a detached house.)

A building where an entrance is shared with more than one dwelling unit is differentiated from a nagaya (it's called an apartment, boarding house or dormitory).

A building of two or more stories in which dwelling units are also divided vertically is further differentiated as an apato (in Japanese pronunciation; actually, an apartment) or a mansion (in Japanese usage; in fact, a condominium).

Nagaya in Japan
The term nagaya normally calls into mind a wooden residential building built along a narrow street of a shitamachi (the traditional shopping, entertainment and residential district). Historically, the style was widely used for traditional urban residential buildings. In castles, a nagaya called the Tamon-yagura (turret) was built on a mound and was used as ordinary residential houses while effectively serving as a point of defense. In particular, the dwelling facility for the goten jochu (palace maids) was called the Nagatsubone (attendants' quarters), and the one in the inner palace of Edo Castle was a two-story, 80-meter-long building in which a lavatory and kitchen were provided for each of the dwelling units.

Nagaya in the Edo period
In the Edo period, merchants of the middle class or higher had their stores facing main streets, but most of the other merchants and craftsmen rented dwellings in nagaya located along the back streets. A nagaya was also built on the premises of daimyo yashiki (mansion of a feudal lord) to accommodate the dwellings of vassals. Particularly, the nagaya situated along back streets of the Edo period presented material very well suited for rakugo (traditional comic storytelling) or senryu (comic haiku). Although they lived in a densely populated condition, people seemed to have lived in an atmosphere of warmth and hospitality.

Most of the nagaya during the Edo period were one-story buildings in which there was a kitchen immediately following an entrance, with just two rooms at the most. A lavatory to be shared was found in a nearby alley, but no bath was provided (the provision of a bath was prohibited due to the possibility that a fire might erupt and cause a disaster). For bathing, public bathhouses were used. Public wells were provided for water. However, they weren't for the use of underground water but for the intake of water from Kanda Josui (Kanda water supply). Therefore, at a well it would take some time before the tub would be sufficiently full of water. While waiting, neighbors would chat, thus giving rise to the expression "idobata-kaigi (literally, a meeting beside a well)." The term "oya (big house)" for a nagaya in the Edo period didn't indicate the owner of the nagaya but a person entrusted with the work of collecting rents and managing the nagaya (roughly equivalent to a property-management company of the present day). The oya often became an adviser to a dweller or dwellers and would handle a dweller's (or dwellers') affairs earnestly. Therefore, the expression "an oya is nearly the same as a parent" frequently appears in rakugo.

There was insufficient space to store many belongings in the small living space of nagaya. Thus, there emerged the sonryo-ya (a lender, equivalent to today's renting business), who lent various things necessary for living to people living in nagaya. The rent for such a dwelling was so inexpensive that a day's earnings could cover it.

Kyu(9)shaku-ni(2)ken-no munewai-nagaya, wari-nagaya (stub)
This term indicates a nagaya in which the dwelling units, each occupying a space of Kyu(9)shaku (approx. 2.7 m) in frontage by ni(2)ken (approx. 3.6 m) in depth, were placed in a row.

The space of a dwelling unit in Kyu(9)shaku-ni(2)ken-no nagaya was roughly equal to that of a six-tatami-mat room, and generally the space corresponding to approximately 1.5-tatami mats was used for the earthen floor and the remaining 4.5-tatami-mat space was used for the room.

Munewari-nagaya indicated nagaya in which walls were placed in the direction parallel with the row, dividing the building into front and rear. In the nagaya of this type, only one side of the structure had an entrance to the outside, leading to poor living environment due to a lack of poor air circulation and light.

For the nagaya in Edo of the Edo period, many yakiya-zukuri (flammable)-style buildings with shingled roofs and clapboards were built, so that in the event of a fire they could easily be replaced.

Nagaya in the modern era
Even in the Meiji period and later, nagaya were generally used as dwellings in urban areas. The number of two-story nagaya (a stair was provided within each dwelling unit) gradually increased, and a lavatory was installed within each dwelling unit. However, scarcely any space for bathing was provided.

Even today, many nagaya still exist, such as in the Tsukishima district of Tokyo. The nagaya was a general dwelling style that existed throughout Osaka and Kyoto as well.

There are many examples of buildings that are seemingly condominiums but are in fact defined as nagaya according to the Building Standard Law. This is because one can build a nagaya even if the building does not meet the conditions for a condominium because the conditions for building a nagaya are less strict. Cases of trouble with nearby residents have been reported when a building that is effectively a condominium is built using this method.