Multifamily residential

Multifamily residential, also known as multidwelling unit (MDU), is a classification of housing where multiple separate housing units for residential inhabitants are contained within one building or several buildings within one complex. Units can be next to each other (side-by-side units), or stacked on top of each other (top and bottom units). Common forms include apartment building and condominium, where typically the units are owned individually rather than leased from a single building owner. Many intentional communities incorporate multifamily residences, such as in cohousing projects.

Housing units in multifamily housing have greater per capita value than single family homes. Multifamily housing has beneficial fiscal externalities, as their presence reduces property tax rates in the community. Contrary to some popular discourse, in particular from NIMBYs, multifamily housing are a lower fire hazard.

Multifamily housing has historically prompted considerable political controversy. In some countries, such as the United States, zoning laws extensively set land aside for detached single-family homes and prohibit multifamily housing. Affluent homeowners have been described as particularly likely to oppose multifamily housing. Historically, efforts to ban multifamily housing were driven by efforts to keep racial minorities and poor people out of neighborhoods.

Before the Industrial Revolution, such examples were rare, existing only in historical urban centers. In Ancient Rome, these were called insulae, skyscrapers in Shibam, malice houses in Madrid, and casbah in the Casbah of Algiers.