Washington: Housing types Note: Single family units can be broken down into attached and detached single family units. Multiple units in structure can be broken down by size: 3-4 units in structure, 5-9 units in structure, 10-19 units in structure, 20-49 units in structure, and 50 or more units in structure. To get this more detailed data, visit the Census Bureau's American Factfinder website: (https://data.census.gov/) These ACS data are estimates based on a five-year average, meaning that data gathered from 2017, 2018, 2019, 2020, and 2021 are averaged together to come up with the results shown here. There is no problem with comparing these data to census data from 2000. For a technical discussion of the "margins of error" associated with ACS estimates, please see: (http://www.census.gov/acs/www/Downloads/data_documentation/Accuracy/MultiyearACSAccuracyofData2010.pdf) (http://www.census.gov/acs/www/Downloads/handbooks/ACSGeneralHandbook.pdf) Source: 1990 and 2000: U.S. Bureau of the Census, Census of Population and Housing, (http://factfinder2.census.gov); 2010-2021: U.S. Bureau of the Census, American Community Survey, American Factfinder, (https://data.census.gov/cedsci/advanced); DATE LAST UPDATED: December 8, 2022.