The "New Residential Construction" report consists of data on the five phases of a residential construction project.

1. This is housing units authorized to be built by a building or zoning permit;
2. Housing units authorized to be built, but not yet started;
   
3. Housing units started;
   
4. Housing units under construction;
   
5. And the final phase....housing units completed.

Estimates of housing units started, but not yet completed, are shown in the "under construction" data series. Housing units under construction are estimated for all areas of the United States, regardless of whether permits are required.

Type of Structure, including Attached and Detached Housing Units

A housing unit, as defined for purposes of this report, is a house, an apartment, a group of rooms or a single room intended for occupancy as separate living quarters. Separate living quarters are those in which the occupants live separately from any other individuals in the building and which have a direct access from the outside of the building or through a common hall.

In accordance with this definition, each apartment unit in an apartment building is counted as one housing unit. Housing units, as distinguished from "HUD-code" manufactured (mobile) homes, include conventional ``site-built'' units, prefabricated, panelized, componentized, sectional, and modular units.

Housing unit statistics exclude group quarters (such as dormitories and rooming houses), transient accommodations (such as transient hotels, motels, and tourist courts), "HUD-code" manufactured (mobile) homes, moved or relocated units, and housing units created in an existing residential or nonresidential structure.

The one-unit structure category includes fully detached, semidetached (semiattached, side-by-side), rowhouses, and townhouses. In the case of attached units, each must be separated from the adjacent unit by a ground-to-roof wall in order to be classified as a one-unit structure. Also, these units must not share heating/air-conditioning systems or interstructural public utilities, such as water supply, power supply, or sewage disposal lines.

Units built one on top of another and those built side-by-side which do not have a ground-to-roof wall and/or have common facilities (i.e., attic, basement, heating plant, plumbing, etc.) are classified by the number of units in the structure (i.e., two-unit structure, three-unit structure, etc.).

Apartment buildings are defined as buildings containing five units or more. Apartments in a conventional-type apartment building may share a common basement, heating plant, stairs, entrance halls, and water supply and sewage disposal facilities. Townhouse apartments, though attached, are not separated by a ground-to-roof wall and/or share some interstructural facilities, such as water supply, sewage disposal, etc.

Geographic regions. The four major regions of the United States for which data are presented in this report represent groups of States as follows:

Northeast: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont, New Jersey, New York, Pennsylvania.

Midwest: Illinois, Indiana, Michigan, Ohio, Wisconsin, Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, South Dakota.

South: Delaware, District of Columbia, Florida, Georgia, Maryland, North Carolina, South Carolina, Virginia, West Virginia, Alabama, Kentucky, Mississippi, Tennessee, Arkansas, Louisiana, Oklahoma, Texas.

West: Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, Wyoming, Alaska, California, Hawaii, Oregon, Washington.