Duplex (building)

A duplex house plan has two living units attached to each other, either next to each other as townhouses, condominiums or one above the other like apartments.

By contrast, a building comprising two attached units on two distinct properties is typically considered semi-detached or twin homes but is also called a duplex in parts of the Northeastern United States, Western Canada, and Saudi Arabia.

In the United Kingdom, the term duplex is sometimes used by property professionals such as architects and estate agents and refers only to a flat or apartment on two floors connected by an inner staircase though many newer apartments have open-plan designs including mezzanines.

In Australia, a duplex is often considered a residential building containing two homes that share a common central wall.

Major Canadian cities sometimes use the term duplex to refer specifically to a building with one unit built above another.

Dallas defines the term duplex as "two dwelling units located on a lot".

In cities such as Buffalo, Detroit and Chicago, the term "two-flat" is used and defines as a "residential building that contains 2 dwelling units located on a single lot.