Triple decker

A certain type of three-story apartment building is often called a triple-decker or three-decker in the United States. These buildings are typically of light-framed, wood construction, where each floor usually consists of a single apartment. Both stand-alone and semi-detached versions are common.

During the late 19th and early 20th centuries, tens of thousands of three-deckers were constructed, mostly in New England, as an economical means of housing the thousands of newly-arrived immigrant workers who filled the factories of the area. The economics of the three-decker are simple: the cost of the land, basement and roof are spread among three or six apartments, which typically have identical floor plans. The three-decker apartment house was seen as an alternative to the row-housing built in other cities of Northeastern United States during this period, such as in New York City, Philadelphia, Baltimore, and Washington, D.C.

Three-deckers were most commonly built in the emerging industrial cities of central New England between 1870 and 1920. There are large concentrations in Massachusetts and Rhode Island. Worcester, Massachusetts, was the likely origin of the type, with Francis Gallagher (1830-1911) held to be the originator. Other cities make the same claim, and they can also be found in the former industrial cities of New Hampshire, Maine, and Connecticut, as well as the New York City area (particularly in northern New Jersey). They were primarily housing for the working-class and middle-class families, often in multiple rows on narrow lots in the areas surrounding the factories. They were regarded as more livable than their brick and stone tenement and row house counterparts, as they allowed for airflow and light on all four sides of each building.

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