ADU

Accessory Dwelling Unit (ADU)

ADU
EXPLORE

Are you hoping to move your family to an ADU on your property, adding a home office, or just plain need more space?

If you are interested in adding an ADU (Accessory Dwelling Unit) to your property you will need a permit. These structures are also known as tiny homes, granny flats, in-law units, mother-in-law apartments, or any other structure that has a kitchen, living space and bathroom separate from the main house.  

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Are you ready to move forward? Here is where to get started:

The Planning Division is where to start for Land Use Approval.  Start by filling out the ADU Land Use Application

Once your Land Use is approved in step 1, and your plans are prepared, you can apply online for your building permits which includes structural, plumbing and mechanical. Electrical permit application will also need to be submitted separately to Washington County directly.

ADU Fees to Expect

To avoid any surprises, plan your budget in advance including all fees.  ADU’s typically incur system development charges (SDC’s) in addition to permit fees for accessory, plumbing or mechanical work.  The fees for an ADU can be 15-25% of your overall budget.  Get a good idea of the fees for each item:

SDC, CET and TDT Fees

  • Parks Residential System Development Charges (SDC)
  • School District Construction Excise Tax (CET)
  • Transportation Development Tax (TDT) using the Residential Condominium/Townhouse rate
  • Water – based on meter size, only charged if upgrading the meter
  • Sewer – Charges based on an additional EDU (1.0)
  • Metro CET – if applicable

Permit Fees

  • Building Permit Fees (Structural)
  • Mechanical Permit Fees
  • Plumbing Permit Fees
  • Electrical Permit Fees (schedule listed with Washington County)

Click to Search all Current Fee Schedules

Fun Fact: The uniform building code for Oregon was established statewide in 1973. This established training requirements for building inspectors.