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    • This is a Non-Federal dataset covered by different Terms of Use than Data.gov.

    Attached Accessory Dwelling Units (AADUs)

    Metadata Updated: November 1, 2025

    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.

    Access & Use Information

    Public: This dataset is intended for public access and use. Non-Federal: This dataset is covered by different Terms of Use than Data.gov. License: See this page for license information.

    Downloads & Resources

    Dates

    Metadata Created Date September 2, 2022
    Metadata Updated Date November 1, 2025

    Metadata Source

    Harvested from Seattle JSON

    Other Data Resources

    Additional Metadata

    Resource Type Dataset
    Metadata Created Date September 2, 2022
    Metadata Updated Date November 1, 2025
    Publisher City of Seattle ArcGIS Online
    Maintainer
    Identifier https://www.arcgis.com/home/item.html?id=b64a1cf17e0a4223a408e411a15029ae&sublayer=0
    Data First Published 2020-01-05
    Data Last Modified 2025-10-28
    Category geospatial
    Public Access Level public
    Metadata Context https://project-open-data.cio.gov/v1.1/schema/catalog.jsonld
    Metadata Catalog ID https://cos-data.seattle.gov/data.json
    Schema Version https://project-open-data.cio.gov/v1.1/schema
    Catalog Describedby https://project-open-data.cio.gov/v1.1/schema/catalog.json
    Harvest Object Id 5dd71502-15be-4f0d-8630-6b387e2e20e1
    Harvest Source Id f61de7a2-69cf-40a9-a1bc-dd9edb8f3fe5
    Harvest Source Title Seattle JSON
    Homepage URL https://data-seattlecitygis.opendata.arcgis.com/datasets/SeattleCityGIS::attached-accessory-dwelling-units-aadus
    License https://opendatacommons.org/licenses/pddl/summary
    Metadata Type geospatial
    Old Spatial -122.4173,47.4938,-122.2427,47.7355
    Source Datajson Identifier True
    Source Hash 2fde00749b3c43433557479fddae2cf66c9d916bc836ec4205c56c58fa4d2989
    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}

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