Accessory Dwelling Units


Accessory Dwelling Units (ADUs) are becoming increasingly popular as a way for communities to create more workforce rental options, while also providing a means to generate income, add housing flexibility, and age-in-place.

You may know these as backyard cottages, mother-in-laws, or granny flats. Whatever you call them, ADUs are one of the most immediate housing solutions available to us. By utilizing the existing space our backyards or easier yet, perhaps in a garage, basement, or attic, we can create flexible workforce rentals.

ADUs are allowed throughout Jefferson County right now. HSN has gathered helpful resources to guide homeowners to starting their own ADU project. We aim to make it easy for you to support workforce housing development here at home.

Are you Considering an ADU?

HSN is committed to enabling more affordable housing in Jefferson County. One of the surest ways we can do that quickly is through utilizing ADUs. If the answer is ‘yes’ to any of these following questions, we’d love to speak with you further.

  • Do you have land where a small, new additional dwelling unit might fit?
  • Do you have a basement, garage or other area where re-modeling might yield a rental unit?
  • Would you like to earn rental income while helping provide more affordable housing?
  • Do you have questions about financing, permitting, or construction that have held you back?
  • Do you want to explore your options now?

Additionally, HSN has produced the Permit Navigator informational video series with local builders and designers that walk the viewer through, step by step, the process of completing an ADU building permit.

Fill out the short form on through this link with as much detailed information as you can and we’ll reach out to start a conversation.

Local Rules

The City and County both allow and encourage ADU development. Key points are:

  • City of PT caps a detached unit size at 800 square feet and an attached unit at 1000, while the County limits all ADUs to1250 square feet
  • Both City and County define an ADU as a complete, independent living facility that has its own address and external entrance
  • In Port Townsend, an owner can rent out both the primary home and the ADU, but in the County you must reside in one of the units.

Jefferson County defines an ADU as, “an additional dwelling unit either in or added to an existing single family detached dwelling, or in a separate accessory structure on the same lot as the main structure, for use as a complete, independent living facility with provisions within the accessory dwelling unit for cooking, eating, sanitation and sleeping.”

Learn more about design, permitting, and other ADU guidelines for the City of Port Townsend and Jefferson County.

Highlighting Local ADU Projects

Build Options


Traditional on-site construction using dimensional lumber.

Commercial Examples

  • Most homes in Jefferson County!


Whole units are built off-site, then delivered and installed. Site work and permitting is still required, as is the interior finish work.

Commercial Examples


Building materials are cut and packaged off-site, and delivered with assembly instructions.

Commercial Examples

Local Advocacy Opportunities

  • ‘Pre-approved ADUs’ are units that have been accepted as well-designed and are permit-able by a municipalities. This can expedite the ADU process for builders. Jefferson County and the City of Port Townsend are both considering following pre-approved models from Clallam County and the City of Seattle. Would you like to see this happen here? Write us and say why!