The number of housing units in the structure in which the unit is located. The number of units in structure includes all housing units whether occupied or vacant, but excludes group quarters or businesses. The statistics are presented in terms of the number of housing units in structures of specified types and sizes, not in terms of the number of structures.

A structure is a separate building that either has open space on all sides or is separated from other structures by dividing walls that extend from ground to roof. This was determined on a sample basis.

A house, apartment, mobile home or trailer, group of rooms, or single room occupied as a separate living quarter or, if vacant, intended for occupancy as a separate living quarter. Separate living quarters are those in which the occupants live and eat separately from any other persons in the building and which have direct access from the outside of the building or through a common hall.

The occupants may be a single family, one person living alone, two or more families living together, or any other group of related or unrelated persons who share living arrangements (except as described in definition of Group Quarters, Persons In). For vacant units, the criteria of separateness and direct access are applied to the intended occupants whenever possible. If that information cannot be obtained, the criteria are applied to the previous occupants. Both occupied and vacant housing units are included in the housing unit inventory, except that recreational vehicles, boats, caves, tents, railroad cars, and the like are included only if they are occupied as someone's usual place of residence. Vacant mobile homes are included provided they are intended for occupancy on the site where they stand. Vacant mobile homes on dealers' sales lots, at the factory, or in storage yards are excluded from the housing inventory. Housing unit status was determined on a complete-count basis.