Accessory Dwelling Unit (ADU)

ADUs are categorized in two ways – attached or detached:

• An attached ADU is part of an existing home (created through a remodel or addition).
• A detached ADU is a completely new structure separate from the existing home, but still on the same single parcel.

Process Overview

Visit our Process Overview page to learn how the process flows from application to occupancy.

Submittal Requirements

• ADU Submittal Requirements
• Review the PDF File Format Requirements for instructions on how to prepare your PDF files
• Review the Soils Report Requirements

Required Forms

• Energy Code Forms (external link)
• King County Sewer Use Certification Form (if applicable)
• Utility Service Application
• Water Meter Sizing Form
• Tree Protection Fence Standard Detail 

Apply Online

Please apply online via MyBuildingPermit.com. We will not accept paper applications or plans.

• Apply Online
• Check Permit Status
• Request Inspections

Fees*

Fees listed below are general fees that are applied to the most common projects. Additional fees including outside, third party, and/or hourly review may apply. See your project’s Land Use or SEPA Notice of Decision for possible additional requirements. Deposits may be required.

• Single Family Fee Estimator

*This information is a general guide and should not be used as a substitute for current codes and regulations. 

Target Review Times

See the Target Review Times Handout (PDF) for target review times. Scope and project complexity may affect review times.