Accessory Structures in Kitsap County, WA (2026)
4 rules for unincorporated Kitsap County, Washington.
Verified from official government sources
ADU Rules
In unincorporated Kitsap County, a detached accessory dwelling unit built outside an urban growth area cannot exceed 900 square feet or half the primary home's habitable area, whichever is smaller, and must sit within 150 feet of the house or convert an existing garage. The owner must occupy either unit, and mobile homes or RVs can never serve as an ADU.
Kitsap County ADU Size and Permit Rules
Some RestrictionsKitsap County Code § 17.415.015
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 pri...
ADU Impact Fees
In unincorporated Kitsap County, road, park and school impact fees on an accessory dwelling unit cannot exceed fifty percent of the fee charged on the principal dwelling. The county still collects the fee before final inspection under Kitsap County Code Chapter 4.110.
Kitsap County ADU Impact Fees Capped at 50%
Some RestrictionsKitsap County Code § 4.110.200(B)
B. Except as otherwise provided for independent fee calculations in Section 4.110.230, exemptions in Section 4.110.030 and credits in Section 4.110.040, all new development other than accessory dwelling units (ADUs) will be charged the road impact fee applicable to the type of development in the road service area in which the development is located. Impact fees on ADUs may not exceed fifty perc...
ADU Owner Occupancy
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.
Kitsap County ADU Owner-Occupancy Rule
Some RestrictionsKitsap County Code § 17.415.015(B)(1)-(3)
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 pri...
Garage Conversions
Outside an urban growth area, unincorporated Kitsap County lets a homeowner convert an existing detached garage into an accessory dwelling unit even if it sits more than 150 feet from the house, but the converted structure must still match the home's appearance and meet every zone setback for its location.
Kitsap County Garage-to-ADU Conversion Rule
Some RestrictionsKitsap County Code § 17.415.015(B)(4)-(6)
4. The ADU shall be located within one hundred fifty feet of the primary residence or shall be the conversion of an existing detached structure (e.g., garage); 5. The ADU shall be designed to maintain the appearance of the primary residence; 6. All setback requirements for the zone in which the ADU is located shall apply;
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