Duplex (building)

An over-and-under two story apartment duplex in Southeastern Pennsylvania

A duplex house plan has two living units attached to each other, either next to each other via townhouses or above each other like apartments.[1] 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.

The term "duplex" is not extended to three-unit and four-unit buildings, as they would be referred to with specific terms such as triplex[2] and fourplex or quadplex/quadruplex.[3] Because of the flexibility of the term, the line between an apartment building and a duplex is somewhat blurred, with apartment buildings tending to be bigger, while duplexes are usually the size of a normal house.

The word "duplex" is occasionally mispronounced with the last letter silent due to multiple misperceptions: (1) that the English word came from French, (2) that an English word naturalized from French needs to retain the French pronunciation, and (3) that the terminal -x would be silent in French. But (1) this English word came straight from educated English speakers' use of Latin (not by way of French), (2) most English words that came from French words use naturalized pronunciation, and (3) the French pronunciation of the French cognate ends in /ɛks/ anyway.


Big cities

A side by side duplex also known as a semi-detached house.

In dense areas like Manhattan and downtown Chicago, a duplex or duplex apartment refers to a maisonette, a single dwelling unit spread over two floors connected by an indoor staircase.[4] Similarly, a triplex apartment refers to an apartment spread out over three floors. These properties can be quite expensive and include the most expensive property in Manhattan as of 2006 (according to Forbes Magazine), a triplex atop The Pierre hotel.[5] In this context, an apartment locating on one floor only may be called a simplex.


In the United Kingdom, the term duplex is more often 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. As such they are usually a mirror image of each other in layout.[6] Also referred to as a maisonette in South Australia.

Paired home

A paired home is two homes that share a wall and have opposite side entries. The whole building is designed to look like one single larger home. Unlike a front to front duplex, the paired home helps provide more privacy for the homeowners.[citation needed]

Other Languages
العربية: مزدوج (سكن)
Deutsch: Doppelhaus
Esperanto: Duplekso
한국어: 땅콩집
Nederlands: Duplexwoning
日本語: メゾネット
Simple English: Duplex
українська: Дуплекс (будівля)
中文: 複式單位