Accessory Structures in Island County, WA (2026)
4 rules for unincorporated Island County, Washington.
Verified from official government sources
ADU Rules
Unincorporated Island County allows one attached or one detached ADU per single-family lot in the Rural, Rural Residential, Rural Agriculture, Rural Forest and Commercial Agriculture zones. Detached units are capped at 1,200 square feet and attached units at 1,000 interior square feet, and the county issues no more than 35 detached-ADU building permits countywide each calendar year.
Accessory Dwelling Unit Rules in Island County
Some RestrictionsIsland County Code § 17.03.180.I
I.Accessory dwelling units (ADUs), attached and detached.1.A detached ADU or an attached ADU may be established in the Rural, Rural Residential, Rural Agriculture, Rural Forest, and Commercial Agriculture Zones.2.No more than one (1) ADU, attached or detached, shall be allowed per single family dwelling unit. ... d.A detached ADU shall not exceed 1,200 square feet of gross floor area. ... h.No ...
ADU Owner Occupancy
In the Freeland zoning code, an attached accessory dwelling unit capped at 1,000 square feet must sit inside a primary home the owner actually occupies, and the ADU's residents cannot run a home occupation or home industry out of the unit.
Attached ADU Owner-Occupancy Rule, Freeland
Some RestrictionsIsland County Code § 17.06.320(A)(6)
6.Attached ADU. In order to encourage the provision of more housing options, attached ADUs may be established, subject to the following criteria.a.No home occupation or home industry shall be permitted for the residents of the attached ADU.b.An attached ADU shall be no greater than 1,000 square feet. ... d.An Attached ADU shall be located within an owner occupied primary residence.
Shed & Carport Rules
In unincorporated Island County's Rural (R) Zone, a shed or other accessory building follows the same setback table as the house it serves. Island County Code section 17.03.060.C makes accessory buildings subject to the yard and road-classification setbacks in the county's general dimensional standards at section 17.03.180.S.
Island County Accessory Building and Shed Setbacks
Some RestrictionsIsland County Code § 17.03.060.C.1
C.Setbacks. Unless otherwise provided in this chapter, setback requirements shall be as follows:1.Setbacks for single family detached dwelling units, mobile/manufactured homes and accessory buildings are specified in section 17.03.180.S.
Tiny Homes
Island County's zoning code expressly excludes 'tiny homes on wheels' from qualifying as an accessory dwelling unit. Section 17.03.040's definition of a detached ADU carves out recreational vehicles, travel trailers, park model homes and tiny homes on wheels, so a wheeled tiny home cannot be permitted through the county's ADU process.
Tiny Homes on Wheels in Island County
Heavy RestrictionsIsland County Code § 17.03.040
Accessory dwelling unit (ADU), Detached means a dwelling unit, situated on the same parcel as a single family dwelling, shares a common access point with the single family dwelling and which cannot be segregated or separately sold, transferred, given, or otherwise conveyed unless the lot is of sufficient size to meet base density and other County Code requirements. Detached ADUs do not include ...
All Island County ordinances
See every category we cover for Island County: parking, noise, fences, fires, animals, pools, and more.
Island County Ordinance Hub →