Two-Family House｜Custom-built homes by architecture firms9Picks｜A Home Where Two Families Coexist Harmoniously

In two-generation residences where parent and child households live under a single roof, the core of the design challenge is how to protect each household’s daily rhythms and privacy while maintaining an appropriate level of connection. Plan typologies vary according to the relationship between households and site constraints — from fully independent units to partially shared arrangements and fully cohabiting layouts. Key issues to address from the design stage include the extent of shared entryways and wet zones, acoustic separation between households, and adaptability to future changes in family composition. Design firms undertake careful interviews to understand the lifestyles and values of both households, and then develop schemes that allow each to be autonomous while naturally supporting one another. We present case studies that respond to the evolving nature of family life.

Located in an urban area of western Saitama Prefecture, this project replaces a long-held family property with a two-family (two-generation) dwelling. The existing garden, with its mature trees, constitutes a valuable remnant of greenery within the block; the design carefully addresses both the preservation of this garden and the spatial relationship between households. Retaining the wisteria pergola, the scheme provides a single shared entrance while otherwise fully separating the two households, and includes two built-in garages. The entrance and garages are located on the west-facing street, and a central hall distributes access to each unit. Each household is organized around a living room that opens onto the garden and takes advantage of the roof slope to define the interior volume. The exterior is expressed as a large mono-pitched roof, with eaves and ceilings finished in solid Nishikawa-sourced hinoki (Japanese cypress) boards.

This two-family residence, comprising two fully independent households, is situated in a densely built area of Nishi-ku, Osaka. Surrounded by a proliferation of three-storey houses, street-facing openings are minimised and an internal courtyard introduced to secure primary daylighting and natural ventilation for both the first and second floors from the courtyard. At the client’s request—whose profession involves sound—a music studio on the second floor has been provided with acoustic treatment and sound insulation.

This is a fully separated two-family residence with high thermal insulation, engineered to seismic Grade 3 performance and augmented by a seismic-damping system. Because the surrounding context does not offer favourable views, the design adopts a courtyard-house typology; the street-facing volume is kept low to respect the streetscape, while inclined walls articulate the building’s relationship with the neighbourhood. A permeable circulation strategy, differentiated floor levels and deliberately controlled ceiling heights by function, together with the use of natural materials, produce a variety of spatial configurations while ensuring daylighting and natural ventilation.

A house set on the eastern foothills of Mount Yamato Katsuragi, crowned by a simple pitched triangular roof. Inhabited by a married couple, the mother, and two cats, the dwelling zones partially overlap to preserve a balanced distance between two-family separation and single-house cohabitation. The couple’s LDK on the ground floor connects to the second-floor landing, bedroom, and wet areas via a double-height stair with large windows and bookshelves. The mother’s program places the bedroom and wet areas on the ground floor and a compact LDK on the second floor. Outside, fields and the seasonal expression of Mount Katsuragi frame a slow-paced atmosphere.

A wood-framed, three-story courtyard house planned on a narrow site enclosed on three sides by neighboring buildings in a densely developed inner-city residential area. Taking advantage of a limited southwest-facing opening, a courtyard and deck terrace are arranged to screen views from the exterior while admitting daylight and natural ventilation, thereby creating a comfortable living environment. The project is conceived as a fully separated two‑generation residence for a dual‑income, music‑enthusiast couple and an aunt who lives with her beloved cat.

This project is a replacement plan for a two-family residence in Nakatsugawa City, Gifu Prefecture. Although the site affords excellent views, it exhibits significant grade differentials both within the lot and relative to adjacent properties. The existing fieldstone retaining wall was old and deteriorated, so determining how to address these elevation changes became a primary design consideration for the rebuild.

The site is located on Yūzō Street, which runs from Chigasaki Station toward the sea. The dwelling is organized around a central courtyard; sago palms, crape myrtles, and white magnolias were transplanted from the garden of the main house, and a timber deck links the two household units. The building is arranged to enclose the courtyard, with perimeter glazing minimized to enhance security. The children’s rooms and the grandparents’ living room face one another across the courtyard. The courtyard is visible from throughout the house, allowing occupants to perceive family presence and movement, resulting in an engaging and pleasant family residence.