Source: U.S. Census Bureau
This series represents the total number of building permits for 1-unit structure types. The 1-unit structure type is a single-family home or house. A single-family home or house types include fully detached, semidetached (semidetached, side-by-side), row houses, and townhouses. For attached units, each must be separated from the adjacent unit by a ground-to-roof wall in order to be classified as a single-family structure. These units also must not share heating/air-conditioning systems or utilities. Units built on top of one another and those built side-by-side that do not have a ground-to-roof wall and/or have common facilities (i.e., attic, basement, heating plant, plumbing, etc.) are not included under single-family structures.
U.S. Census Bureau, New Private Housing Units Authorized by Building Permits: 1-Unit Structures for Maine [MEBP1FH], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/MEBP1FH, July 6, 2022.