A housing unit is "owner occupied" if the owner or co-owner lives in the unit even if the unit is mortgaged or not fully paid for. The owner or co-owner must live in the unit but need not be the person listed in column 1 of the 1980 census questionnaire.

All occupied housing units which are not owner occupied, regardless of whether cash rent is paid by a member of the household. ("No cash rent" units, a subcategory of renter occupied, are separately identified in rent tabulations. Such units are generally one provided free by friends or relatives, or in exchange for the services of, for example, a caretaker, minister, tenant farmer, or sharecropoer.)

Tenure has been collected since 1890. In 1970, the question on tenure also included a category for condominium and cooperative ownership. In 1980, condominiums are identified in a separate question.

See also: "Condominium Status;" "Owner Costs, Selected Monthly;" "Rent, Contract;" "Rent, Gross;" "Value".

Synonymous with 1-unit structure (i.e., the term does not imply occupancy by a family as defined for census purposes). This category excludes mobile homes or trailers as defined below.

1-unit structure detached from any other house, i.e., with open space on all four sides. Such structures are considered detached even if they have an adjoining shed or garage. A one-family house which contains a business is considered detached as long as the building has open space on all four sides. Mobile homes or trailers to which one or more permanent rooms have been added or built on are also included.

1-unit structure which has one or more walls extending from ground to roof separating it from adjoining structures. In row houses (sometimes called townhouses), double houses, or houses attached to nonresidential structures, each house is a separate attached structure if the dividing or common wall goes from ground to roof.

Units in structures containing 2 or more housing units; further categorized as units in structures with 2, 3 or 4, 5 to 9, 10 to 19, 20 to 49, and 50 or more units.

Both occupied and vacant mobile homes to which permanent rooms have been added. If only a porch or shed has been added, the unit is counted in this category. Note that mobile homes or trailers used only for business purposes or for extra sleeping space, and mobile homes or trailers for sale on a dealer's lot at the factory, or in storage are not counted in the housing inventory. In the printed reports, this category includes occupied housing units indicated as "boat, tent, van, etc.," i.e., any occupied units which do not fit the other listed categories. Houseboats, railroad cars, campers, and caves used as a usual place of residence provide additional examples.

Users of small-area data occasionally are troubled by certain anomalies in units-in-structure data. For example, a user may encounter a table in which only 5 units in a census tract are listed as being in a structure of 10 or more units. Sometimes respondents do not know the exact number of units in a structure and give an incorrect response.

Data have been collected on units in structure since 1940 and on mobile homes and trailers since 1950.

The residual category "boat, tent, van, etc." replaces the 1970 category "other--describe." The instruction to respondents that a mobile home or trailer counts as a detached house if a room (though not a porch or shed) has been built on to it was added in 1970 and retained for 1980.

See also: "Units at Address".