Townhouse and duplex are two types of construction properties; both of them are used for residential purposes.
Townhouse and duplex are building structures that are shared between different families and do not have single ownership. However, there are several differences in their construction and the physical layout and knowledge of these differences can help you in making an informed decision while dealing with property matters.
The basic difference between these two lies in the number of dwellings they contain. A duplex is commonly a two story building; each story has an apartment which houses a separate family. The apartments are self-contained and have separate entrances, however, they do share a common wall.
Townhouses are composed of several housing units, characterized by their terrace feature and can house several families. So a duplex has just two apartments while a townhouse can have more than two dwellings.
Duplex and townhouses also differ in the fashion of construction. Duplex apartments are built directly upon each other in story fashion and can also be built side by side. Townhouses are different; the housing units are not built upon each other but in a row fashion, side by side. This is the reason why modern townhouses are also known as row houses. A townhouse is therefor an extended model of a duplex apartments built side by side.
The land ownership is also different between these two structures. In a townhouse, each unit also owns the land underneath his respective dwelling. In a duplex, the land underneath both the units is owned by a single owner.
Typically, one of the two duplex residents pay rental fee, which is usually paid to the other resident who is the owner of the whole property. In some circumstances, both the residents can be tenants to a third owner.