Attached Accessory Dwelling Units (AADUs)

Permit records from the City of Seattle permitting system for building permits that create or demolish attached accessory dwelling units (AADU). Records begin in 1990 and are through the current year quarter.The permits in this layer are those that have either been completed or are currently issued. This data does not contain records for those permits that were issued but were not completed so are therefore not comparable to statistics that report permit issuance.Each record represents the number of units added or demolished for each housing type in the project. Therefore a single building permit may appear multiple times if there are a mix of unit types in the project.Housing unit types reflect the unit types regulated by the building codes and change through time. There has been no attempt to standardize these types and therefore reflect the unit types that existed at the time the permit was issued. Unit types will be visible only for the time period they were in the code. For example, small efficiency dwelling units were not created in the code until 2016 and so will not appear as a type until that year.There may be multiple permits at any given address.

Data and Resources

Field	Value
accessLevel	public
catalog_@context	https://project-open-data.cio.gov/v1.1/schema/catalog.jsonld
catalog_@id	https://cos-data.seattle.gov/data.json
catalog_conformsTo	https://project-open-data.cio.gov/v1.1/schema
catalog_describedBy	https://project-open-data.cio.gov/v1.1/schema/catalog.json
identifier	https://www.arcgis.com/home/item.html?id=b64a1cf17e0a4223a408e411a15029ae&sublayer=0
issued	2020-01-05
landingPage	https://data-seattlecitygis.opendata.arcgis.com/datasets/SeattleCityGIS::attached-accessory-dwelling-units-aadus
license	https://opendatacommons.org/licenses/pddl/summary
metadata_type	geospatial
modified	2025-08-19
old-spatial	-122.4173,47.4938,-122.2427,47.7355
publisher	City of Seattle ArcGIS Online
resource-type	Dataset
source_datajson_identifier	true
source_hash	02339234fe33d9f1c79942b93a7fc02ab095a579799503f6abdcf45427a75da6
source_schema_version	1.1
spatial	{"type": "Polygon", "coordinates": [[[-122.4173, 47.4938], [-122.4173, 47.7355], [-122.2427, 47.7355], [-122.2427, 47.4938], [-122.4173, 47.4938]]]}
theme	{geospatial}
Groups	AmeriGEOSS National Provider North America
Tags	AmeriGEO AmeriGEOSS CKAN GEO GEOSS National North America United States adu aduapp gis housing-units permits planning seattle-gis-open-data
isopen	False
license_id	other-license-specified
license_title	other-license-specified
maintainer	Planning_SeattleCityGIS
maintainer_email	mapgis.mapgis@seattle.gov
metadata_created	2025-09-23T22:52:39.609385
metadata_modified	2025-09-23T22:52:39.609451
notes	<p style='font-family:"Avenir LT W01 35 Light", "Avenir Next", Avenir, "Helvetica Neue", Helvetica, Arial, sans-serif; font-size:16px;'>Permit records from the City of Seattle permitting system for building permits that create or demolish attached accessory dwelling units (AADU). Records begin in 1990 and are through the current year quarter.</p><p style='font-family:"Avenir LT W01 35 Light", "Avenir Next", Avenir, "Helvetica Neue", Helvetica, Arial, sans-serif; font-size:16px;'></p><p style='font-family:"Avenir LT W01 35 Light", "Avenir Next", Avenir, "Helvetica Neue", Helvetica, Arial, sans-serif; font-size:16px;'>The permits in this layer are those that have either been completed or are currently issued. This data does not contain records for those permits that were issued but were not completed so are therefore not comparable to statistics that report permit issuance.</p><p style='font-family:"Avenir LT W01 35 Light", "Avenir Next", Avenir, "Helvetica Neue", Helvetica, Arial, sans-serif; font-size:16px;'></p><p style='font-family:"Avenir LT W01 35 Light", "Avenir Next", Avenir, "Helvetica Neue", Helvetica, Arial, sans-serif; font-size:16px;'>Each record represents the number of units added or demolished for each housing type in the project. Therefore a single building permit may appear multiple times if there are a mix of unit types in the project.</p><p style='font-family:"Avenir LT W01 35 Light", "Avenir Next", Avenir, "Helvetica Neue", Helvetica, Arial, sans-serif; font-size:16px;'></p><p style='font-family:"Avenir LT W01 35 Light", "Avenir Next", Avenir, "Helvetica Neue", Helvetica, Arial, sans-serif; font-size:16px;'>Housing unit types reflect the unit types regulated by the building codes and change through time. There has been no attempt to standardize these types and therefore reflect the unit types that existed at the time the permit was issued. Unit types will be visible only for the time period they were in the code. For example, small efficiency dwelling units were not created in the code until 2016 and so will not appear as a type until that year.</p><p style='font-family:"Avenir LT W01 35 Light", "Avenir Next", Avenir, "Helvetica Neue", Helvetica, Arial, sans-serif; font-size:16px;'></p><p style='font-family:"Avenir LT W01 35 Light", "Avenir Next", Avenir, "Helvetica Neue", Helvetica, Arial, sans-serif; font-size:16px;'>There may be multiple permits at any given address.</p>
num_resources	11
num_tags	15
title	Attached Accessory Dwelling Units (AADUs)