A three-decker is the U.S. term for a type of vertical
triplex apartment building
An apartment (American English, Canadian English), flat (British English, Indian English, South African English), tenement ( Scots English), or unit (Australian English) is a self-contained housing unit (a type of residential real estate) ...
. These detached three-story buildings are typically of
light-framed, wood construction, where each floor usually consists of a single apartment. Both stand-alone and
semi-detached
A semi-detached house (often abbreviated to semi) is a single-family Duplex (building), duplex dwelling that shares one common party wall, wall with its neighbour. The name distinguishes this style of construction from detached houses, with no sh ...
versions are common.
During the late 19th and early 20th centuries, tens of thousands of three-deckers were constructed, mostly in
New England
New England is a region consisting of six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York (state), New York to the west and by the ...
, as a cheap means of housing the thousands of newly arrived immigrant workers who filled the region’s factories. A typical tree-decker contained three apartments, usually with identical floor plans. The three-decker apartment house was seen as an alternative to narrow single-unit
row-housing built in other cities of
Northeastern United States
The Northeastern United States (also referred to as the Northeast, the East Coast, or the American Northeast) is List of regions of the United States, census regions United States Census Bureau. Located on the East Coast of the United States, ...
during this period, such as
New York City
New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...
,
Boston
Boston is the capital and most populous city in the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States. The city serves as the cultural and Financial centre, financial center of New England, a region of the Northeas ...
,
Philadelphia
Philadelphia ( ), colloquially referred to as Philly, is the List of municipalities in Pennsylvania, most populous city in the U.S. state of Pennsylvania and the List of United States cities by population, sixth-most populous city in the Unit ...
,
Baltimore
Baltimore is the most populous city in the U.S. state of Maryland. With a population of 585,708 at the 2020 census and estimated at 568,271 in 2024, it is the 30th-most populous U.S. city. The Baltimore metropolitan area is the 20th-large ...
, and
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly known as Washington or D.C., is the capital city and federal district of the United States. The city is on the Potomac River, across from Virginia, and shares land borders with ...
Originally, extended families often lived in two or all three floors. Some three-deckers were divided into six units.
Three deckers often account for a disproportionate number of structure fires.
History

Three-deckers were most commonly built in the emerging industrial cities of central
New England
New England is a region consisting of six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York (state), New York to the west and by the ...
between 1870 and 1920. There are large concentrations in
Massachusetts
Massachusetts ( ; ), officially the Commonwealth of Massachusetts, is a U.S. state, state in the New England region of the Northeastern United States. It borders the Atlantic Ocean and the Gulf of Maine to its east, Connecticut and Rhode ...
and
Rhode Island
Rhode Island ( ) is a state in the New England region of the Northeastern United States. It borders Connecticut to its west; Massachusetts to its north and east; and the Atlantic Ocean to its south via Rhode Island Sound and Block Is ...
.
Worcester, Massachusetts
Worcester ( , ) is the List of municipalities in Massachusetts, second-most populous city in the U.S. state of Massachusetts and the list of United States cities by population, 113th most populous city in the United States. Named after Worcester ...
, was the likely origin of the type, attributed to Francis Gallagher (1830–1911), though other cities make the same claim. Three-deckers can be found in the former industrial centers of
New Hampshire
New Hampshire ( ) is a U.S. state, state in the New England region of the Northeastern United States. It borders Massachusetts to the south, Vermont to the west, Maine and the Gulf of Maine to the east, and the Canadian province of Quebec t ...
,
Maine
Maine ( ) is a U.S. state, state in the New England region of the United States, and the northeasternmost state in the Contiguous United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Provinces and ...
, and
Connecticut
Connecticut ( ) is a U.S. state, state in the New England region of the Northeastern United States. It borders Rhode Island to the east, Massachusetts to the north, New York (state), New York to the west, and Long Island Sound to the south. ...
, as well as the New York City area (particularly in
northern New Jersey and
Yonkers
Yonkers () is the List of municipalities in New York, third-most populous city in the U.S. state of New York (state), New York and the most-populous City (New York), city in Westchester County, New York, Westchester County. A centrally locate ...
) and Upstate New York, where they are commonly seen as far west as
Utica. Three-deckers are also found in Canadian cities with strong ties to New England, particularly
Halifax, though they are less ubiquitous.
Three-deckers were primarily housing for
working-class
The working class is a subset of employees who are compensated with wage or salary-based contracts, whose exact membership varies from definition to definition. Members of the working class rely primarily upon earnings from wage labour. Most c ...
and
middle-class
The middle class refers to a class of people in the middle of a social hierarchy, often defined by occupation, income, education, or social status. The term has historically been associated with modernity, capitalism and political debate. Commo ...
families, often in multiple rows on narrow lots in the areas surrounding the factories. They were derided as poor-quality buildings, shoddily constructed from flammable
balloon framing: a 1911 report by the Massachusetts State Housing Committee in Massachusetts decried the three-decker as "a flimsy fire-trap and a menace to human life".
Anti-immigrant sentiment led to the Tenement Act in Massachusetts in 1912, which allowed municipalities to ban three-deckers; many did.
It is estimated that by 1920 the city of
Boston
Boston is the capital and most populous city in the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States. The city serves as the cultural and Financial centre, financial center of New England, a region of the Northeas ...
had over 15,000 three-decker houses. Areas such as
Dorchester,
Roxbury,
Mattapan, and
Jamaica Plain
Jamaica Plain is a Neighborhoods in Boston, neighborhood of in Boston, Massachusetts, United States. Settled by Puritans seeking farmland to the south, it was originally part of Roxbury, Massachusetts, Roxbury. The community seceded from Roxbur ...
were popular with the emerging middle class and became "
streetcar suburbs
A streetcar suburb is a residential community whose growth and development was strongly shaped by the use of streetcar lines as a primary means of transportation. Such suburbs developed in the United States in the years before the automobile, whe ...
" as transportation systems expanded from the older, core sections of the city. Typically, the affordable three-decker homes attracted live-in landlords who would collect rent from the other two apartments.
In
Worcester, Massachusetts
Worcester ( , ) is the List of municipalities in Massachusetts, second-most populous city in the U.S. state of Massachusetts and the list of United States cities by population, 113th most populous city in the United States. Named after Worcester ...
, sewer connection charges were based on street frontage, so builders favored houses with as little frontage as possible. This is one reason why three-deckers are often situated on narrow lots with their smaller sides at the front and rear.
In the textile mill city of
Fall River, Massachusetts
Fall River is a city in Bristol County, Massachusetts, United States. Fall River's population was 94,000 at the 2020 United States census, making it the List of municipalities in Massachusetts, tenth-largest city in the state, and the second- ...
, thousands of wood-framed multi-family tenements were built by the mill owners during the boom years of the 1870s to house their workers. Many more were built by private individuals who rented their apartments to the mill workers and their families. This style of housing differed greatly from the well-spaced boardinghouses of the early 19th century built in
Lowell and
Lawrence, Massachusetts
Lawrence is a city located in Essex County, Massachusetts, United States, on the Merrimack River. At the 2020 United States census, 2020 census, the city had a population of 89,143. Surrounding communities include Methuen, Massachusetts, Methuen ...
, or the cottages of Rhode Island.
A different three-story style apartment house is also common in urban working-class neighborhoods in northern New Jersey (particularly in and around
Newark,
Jersey City
Jersey City is the List of municipalities in New Jersey, second-most populous and
Paterson). They are sometimes locally referred to as "
Bayonne
Bayonne () is a city in southwestern France near the France–Spain border, Spanish border. It is a communes of France, commune and one of two subprefectures in France, subprefectures in the Pyrénées-Atlantiques departments of France, departm ...
Boxes".
Similar brick apartment buildings were built in
Chicago
Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...
in the 1910s and 1920s. There they are locally referred to as "Three Flats".
Structure and variations
Three-deckers are usually defined by the style of their roofs, being either
gable
A gable is the generally triangular portion of a wall between the edges of intersecting roof pitches. The shape of the gable and how it is detailed depends on the structural system used, which reflects climate, material availability, and aesth ...
,
hip
In vertebrate anatomy, the hip, or coxaLatin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) (: ''coxae'') in medical terminology, refers to either an anatomical region or a joint on t ...
, or
flat-roofed, with preference often varying regionally. For instance, hipped and gabled three-deckers are dominant in Worcester. In smaller cities, such as Lawrence or Albany, New York, two or two and a half story variants are common, while retaining a similar overall typology, with a bay window on the front, and prominent porches.
Various external features typify the three-decker. Windows are usually located on all four sides of the building, including a street-facing
bay window
A bay window is a window space projecting outward from the main walls of a building and forming a bay in a room. A bow window is a form of bay with a curve rather than angular facets; an oriel window is a bay window that does not touch the g ...
on each floor. Utility porches are located in the rear, and typically not visible from the street. Some three-deckers feature a single front door that access all three units; others feature one entrance for the bottom floor and one that accesses the top two. While usually lacking the ornamentation found on other homes of the
Victorian era
In the history of the United Kingdom and the British Empire, the Victorian era was the reign of Queen Victoria, from 20 June 1837 until her death on 22 January 1901. Slightly different definitions are sometimes used. The era followed the ...
, three-deckers were sometimes built with decorative details such as porch railings and posts.
Three-deckers are constructed from wood and typically use
balloon framing, which makes them especially susceptible to destructive fires.
Boston-based
''GBH News'' noted that "fire officials in Worcester, Fall River,
Brockton and
New Bedford
New Bedford is a city in Bristol County, Massachusetts, United States. It is located on the Acushnet River in what is known as the South Coast (Massachusetts), South Coast region. At the 2020 United States census, 2020 census, New Bedford had a ...
all say a disproportionate majority of their structure fire response involves the buildings."
Other common contributors to the flammability of three-deckers include primitive electrical systems such as
knob-and-tube wiring, antiquated
natural gas
Natural gas (also fossil gas, methane gas, and gas) is a naturally occurring compound of gaseous hydrocarbons, primarily methane (95%), small amounts of higher alkanes, and traces of carbon dioxide and nitrogen, hydrogen sulfide and helium ...
appliances such as gas-on-gas stoves, and petroleum-based
shingle siding.
Legacy

Three-deckers were built in large numbers, in some areas comprising entire neighborhoods, but by the 1950s, a number of them had been abandoned or razed because of
suburb
A suburb (more broadly suburban area) is an area within a metropolitan area. They are oftentimes where most of a metropolitan areas jobs are located with some being predominantly residential. They can either be denser or less densely populated ...
an growth and
urban renewal
Urban renewal (sometimes called urban regeneration in the United Kingdom and urban redevelopment in the United States) is a program of land redevelopment often used to address real or perceived urban decay. Urban renewal involves the clearing ...
.
Their reputation as poor quality and dangerous persisted into the 1970s.
Starting in the early 1980s, however, they became desirable again as older
streetcar suburbs
A streetcar suburb is a residential community whose growth and development was strongly shaped by the use of streetcar lines as a primary means of transportation. Such suburbs developed in the United States in the years before the automobile, whe ...
began to
gentrify
Gentrification is the process whereby the character of a neighborhood changes through the influx of more affluent residents (the "gentry") and investment. There is no agreed-upon definition of gentrification. In public discourse, it has been us ...
, often by buyers looking for homes where they could live in one unit and
rent the other two, thus helping them pay their
mortgage
A mortgage loan or simply mortgage (), in civil law (legal system), civil law jurisdictions known also as a hypothec loan, is a loan used either by purchasers of real property to raise funds to buy real estate, or by existing property owners t ...
. As
condominium
A condominium (or condo for short) is an ownership regime in which a building (or group of buildings) is divided into multiple units that are either each separately owned, or owned in common with exclusive rights of occupation by individual own ...
s became more common, many were converted into individually-owned units.
Since 1990, many three-deckers in Worcester, Massachusetts, have been listed on the
National Register of Historic Places
The National Register of Historic Places (NRHP) is the Federal government of the United States, United States federal government's official United States National Register of Historic Places listings, list of sites, buildings, structures, Hist ...
.
Recently, a new wave of three-decker apartment houses has been built in areas of Boston as an alternative to the
townhouse
A townhouse, townhome, town house, or town home, is a type of Terraced house, terraced housing. A modern townhouse is often one with a small footprint on multiple floors. In a different British usage, the term originally referred to any type o ...
style condominium or apartment buildings more typically associated with suburban areas. Boston's zoning regulations allow new three-family houses to be constructed in areas with existing three-deckers. However, building codes for the new buildings are far more stringent today, with requirements for
fire sprinkler
A fire sprinkler or sprinkler head is the component of a fire sprinkler system that discharges water when the effects of a fire have been detected, such as when a predetermined temperature has been exceeded. Fire sprinklers are extensively used ...
systems and handicap access.
Second Act for triple-deckers
Somerville, Massachusetts
Somerville ( ) is a city located directly to the northwest of Boston, and north of Cambridge, Massachusetts, Cambridge, in Middlesex County, Massachusetts, United States. As of the 2020 United States census, the city had a total population of 81, ...
re-legalized the structures in 2019 and removed many restrictions in 2023 to comply with the MBTA Communities Act.
See also
* 5-over-1
* Affordable housing
Affordable housing is housing which is deemed affordable to those with a household income at or below the median, as rated by the national government or a local government by a recognized housing affordability index. Most of the literature on ...
* List of house types
This is a list of house types. Houses can be built in a large variety of configurations. A basic division is between free-standing or single-family detached homes and various types of attached or multi-family residential dwellings. Both may vary ...
* List of Registered Historic Places in Worcester, Massachusetts
* Polish flat
References
{{Reflist
External links
Worcester Historical Museum
Sightseeking, 2005
New England