ADU, Accessory Dwelling Units
What is an ADU?
An ADU is a housing unit. An Accessory Dwelling Unit (ADU) is one or more rooms with a private bath and kitchen facilities comprising an independent, self-contained dwelling unit within or attached to a single-family dwelling or in a detached building on the same lot as a primary dwelling unit.
An ADU is legal only with an established building permit.
For a complete listing of zoning code requirements for accessory dwelling units, please refer to VMC 20.810 Accessory Dwelling Units.
This project may be eligible for tax relief for up to three years.
Note: You must file your application with the Assessor’s Office before construction is completed.
- Clark County Assessor – Homeowner’s Remodel Exemption
- Improvements to single-family dwellings, including both attached and detached ADUs
What is the process for building an ADU?
ADUs, as any new housing unit, must have a building permit, including those created inside an existing home through remodel or addition.
Residential construction of 1-6 housing units on one lot and three (3) or fewer floors above grade will be processed as a Residential (RES) permit.
Prior to submitting a residential building application for new housing, including accessory dwelling units, applicants must submit a Request for Utility Services and receive the results to determine if a civil engineering review (ENG) is needed.
If there is no associated land division, a land use process (LUP application) is not required.
Start with Plan Your Project and open the dropdown for Prepare at Residential Building Permits.
Where can I build an ADU?
ADUs are allowed as limited uses on all lots.
How many ADUs can I build on a single lot?
Currently two units can be built on a single lot. Starting 7/31/2026, more residential structures can be built on a single lot and up to two of those can be ADUs provided they meet the maximum size and other requirements.
Are owners required to live on the property?
No, the property owner is not required to live on the property where an ADU is located.
What are the size limitations for an ADU?
An ADU shall not exceed 1,000 square feet.
The gross floor area of an ADU shall not be less than the requirements of the Washington State Building Code.
Is on-site parking required for an ADU?
Applications received before 7/31/2026 cannot eliminate the required parking for the main dwelling. The main dwelling is required a minimum of one parking space, which can be in a garage or an approved 9’x17’ pad attached to a driveway on the property.
Does an ADU need to be visually subordinate to the main dwelling?
An ADU no longer needs to visually subordinate to the main dwelling, nor architecturally compatible with the principal dwelling.
What are the required setback and lot coverage requirements for an ADU?
An ADU addition to an existing house or the construction of a new ADU shall not exceed the allowable lot coverage or encroach into required setbacks as prescribed in the underlying zone for the primary structure.
Can I convert my existing accessory structure into an ADU?
Yes, an existing garage structure or other outbuilding may be converted to an ADU.
Which energy forms are required?
Energy Forms are required for new dwellings, when adding new dwelling area, and when converting unheated space to heated space. When building a new home and an ADU at the same time, separate energy compliance forms are required for each dwelling.
How do I know if I have adequate electrical service?
Contact Clark Public Utilities at 360-992-8558 to request verification of transformer capacity.
Will existing overhead electrical lines need to be moved?
If you are enlarging your home (an addition) or building a new detached ADU, contact Clark Public Utilities at 360-992-8558 to request required clearances of overhead lines.
Should I hire a professional to design my ADU?
It is not required, however due to the complexity of these projects, we recommend that you hire a professional to assist in the design process.
Additional questions?
For questions on setbacks or development standards, please email cddplanning@cityofvancouver.us
For building code questions, please email planreview@cityofvancouver.us