semidetached

Semidetached, or a semi-detached house, refers to a single-family dwelling that shares exactly one wall with a neighboring home. The pair is usually built as mirror images or closely matched designs, forming a semi that occupies two adjacent lots but remains two separate residences with independent entrances and no internal access between the units. Each dwelling typically includes its own front and rear garden or outdoor space.

Common in the United Kingdom, Ireland, Australia, and New Zealand, semidetached houses are a staple of suburban streets. In North America, similar structures are more often described as duplexes or two-family homes, though the term semi-detached may be used in some markets. The architectural style varies, but many semis feature two stories, with living areas on the ground floor and bedrooms above, and layouts that emphasize a logical separation between the two units.

Design and construction vary, but semidetached houses typically provide a balance between privacy and efficient land use. They often offer more space and amenities than a terraced unit while remaining more affordable and easier to maintain than a fully detached house. The shared wall can improve energy efficiency compared with two completely separate houses of similar size, though it may also raise concerns about sound transmission and boundary management.

Ownership and planning considerations include maintaining one’s own unit while sharing responsibility for the party wall and any common elements with the neighbor. Alterations near the shared wall may require notice or agreement under local property or party-wall regulations. Market value and appeal depend on location, condition, and access to nearby services and transportation.