Kitsap County, WA Accessory Structures: ADU Owner Occupancy (2026)
Key Facts
- Who must live on-site
- Owner must occupy primary residence or the ADU
- Applies to
- Detached ADUs outside an urban growth area only
- Units per lot
- Only one ADU allowed per lot
- Size cap
- 900 sq ft or 50% of home's habitable area, smaller
- Legalization path
- Type II permit under Chapter 21.04 for unpermitted units
- Enforcing office
- Kitsap County Department of Community Development
- Last amended
- Ordinance 611 (2022) § 185
Summary
Outside an urban growth area, a detached accessory dwelling unit on unincorporated Kitsap County land is only legal if the property owner lives in either the main house or the ADU. Only one ADU is allowed per lot, and it is capped at 900 square feet or half the primary home's habitable area, whichever is smaller.
B. In order to encourage the provision of affordable housing, an accessory dwelling unit (ADU), detached, located outside an urban growth area shall meet the following criteria: 1. Only one ADU shall be allowed per lot; 2. Owner of the property must reside in either the primary residence or the ADU; 3. The ADU shall not exceed fifty percent of the square footage of the habitable area of the primary residence or nine hundred square feet, whichever is smaller. Dimensions are determined by interior measurements;
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4864424; v0 updated 2025-12-08; through 12-08-2025).
Full Breakdown
010, which allows up to two ADUs per lot capped at 1,000 square feet with no owner-occupancy requirement. Outside a UGA, subsection (B)(2) requires that the owner of the property reside in either the primary residence or the ADU; the county pairs that with a one-ADU-per-lot cap in (B)(1) and a size cap in (B)(3) of fifty percent of the primary residence's habitable area or nine hundred square feet, whichever is smaller, measured by interior dimensions. The ADU must meet applicable health district standards for water and sewage disposal under (B)(7), all zone setbacks under (B)(6), and cannot be a mobile home or recreational vehicle under (B)(8).
It must share the same side-street entrance as the primary residence and add off-street parking under (B)(9), and a lot cannot carry both a detached ADU and an attached ADU (ADU-A) at the same time under (B)(10). 10, and documenting they did not build the unit, did not own the property when it was built, and exercised due diligence before buying. This section was last amended by Ordinance 611 (2022) § 185.
Violations & Fines
A detached ADU outside a UGA where the owner lives off-site, where a second detached ADU sits on the same lot, or where the unit exceeds the 900-square-foot/50%-of-habitable-area cap does not meet § 17.415.015(B) and cannot be permitted as submitted. An ADU built without review is an unpermitted structure; the owner must either bring it into compliance or, if it qualifies under (B)(11), file a Type II permit application with the Department of Community Development, pay the resolution-set fee plus any notification and reinspection costs, and record a land use permit binder with the county auditor once approved, or the unit remains a code violation subject to enforcement.
Frequently Asked Questions
Must I personally live in the ADU to build one outside a UGA?
How big can a detached ADU be outside a Kitsap County UGA?
What if I already built an ADU outside a UGA without a permit?
Sources & Official References
Other rules in Kitsap County
Compare Kitsap County to another location·View the Washington accessory structures overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.