Although there are sharp differences between houses from various regions of Japan in terms of roof shape and roofing material, for example, many features are common. In general, all houses contain tatami (thick straw mats) for flooring. The size of the mats is standard so the layout of all rooms conforms to set sizes: 3 mats, 4.5 mats, 6 mats, 8 mats and so on. There is a distinct entry area where shoes are taken off before stepping up to the tatami rooms which are on a raised platform. Wood-floored corridors run between the rooms, leading to utility areas such as the kitchen, toilets, and bathroom (the last two are always separate). Most houses will also have special areas reserved for family alters or shrines, normally in the best room. There are no bedrooms as such. Instead, bedding is stored in closets with sliding doors so that each room doubles as a living area by day and bedroom at night. Rooms are separated by light-weight sliding screens (either shoji covered with translucent paper or fusuma which have covering of opaque decorated paper): both can be removed to create greater space.
The principal distinction in house architecture is the difference between the design of a town house and that of a farm house. Town houses are constructed in a regular fashion all facing a street and separated only by a common wall which often was fire-proof. The width of frontage on the street was determined by status. Low-ranking townspeople were only allowed a narrow frontage, but the structure often ran a considerable distance back from the street. This applied equally to inns and commercial establishments. In such cases, the business area was at the front and the family residence, kitchen, and storerooms were far to the back.
Farm houses, on the other hand, were loosely clustered in a village setting. More space was available than in the towns so houses could be detached from one another and there was space for storehouses and other outbuildings as well as a small garden. The internal arrangement of rooms was usually regular with four large rooms arranged in a square shape, separated by sliding screens. Utility areas like the kitchen were placed on one side of these rooms, on the earthen floor.
In the traditional architecture of the town house and the farm house, the living area was generally arranged on the ground floor; second story structures were usually found in the roof space and were only used for storage. Low-rise construction is characteristic, therefore, in both urban and rural areas. This helps reduce damage by earthquakes, but has led to sprawling settlements.
