ADU Pass
Clinton
ADU Pass helps homeowners in Clinton, Island County, Washington navigate the permit paperwork for building an accessory dwelling unit. This area covers 1 ZIP code.
Map
ADU details
ADU legality: allowed
Washington preempts most local ADU restrictions. Clinton permits ADUs by right in single-family zones per its zoning ordinance.
Cost scenarios
| Scenario | Sq ft | Permit | Build | Total |
|---|---|---|---|---|
| minimum | 150 | $2,900 | $48,750 | $51,650 |
| 600 | 600 | $2,900 | $195,000 | $197,900 |
| midpoint | 675 | $2,900 | $219,375 | $222,275 |
| maximum | 1,200 | $2,900 | $390,000 | $392,900 |
Fee breakdown (as of 2026-04)
Permitting process
- Pre-application septic and well evaluation (~30d)
Clinton parcels are nearly all septic-served. Island County Environmental Health requires septic capacity verification (existing OSS designed for ADU load, or replacement system designed) before any building permit submittal. Well capacity test required if shared/single private well. - Zoning verification under ICC Title 17 (~7d)
Confirm parcel zoning (Rural, Rural Residential, or Rural Center for Clinton corridor), check density credit availability, verify shoreline setbacks if within 200 ft of Possession Sound or Saratoga Passage (SMP jurisdiction), check critical areas (CAO) for wetlands, geologic hazards, fish-and-wildlife habitat. - Submit via SmartGov Public Portal or in person at Coupeville (~1d)
Submit Single-Family Residence/Det. ADU Application or Detached Accessory Structure Application through Island County Public Portal at co-island-wa.smartgovcommunity.com, or paper at 1 NE 7th Street, Coupeville. Include site plan, septic-as-built, floor plans, elevations, energy code worksheet (WSEC 2021), and structural plans. - Sequential review (no concurrent track) (~60d)
Island County reviews planning/zoning first, then environmental health (septic/well), then building/structural, then fire. Each handoff resets queue position. Whidbey-permit-counter staffing is limited so reviews back up seasonally. - Address corrections (~30d)
Typical 2-3 correction cycles for owner-builder; 1-2 for licensed-GC submittals. Each cycle adds ~3 weeks at the Whidbey counter. - Permit issuance (~5d)
Pay building, plan review, environmental health septic review, address-assignment, and WA State surcharge fees. Permit issued through SmartGov; print and post on site. - Inspections via SmartGov
Setback, footing, foundation, septic connection (Environmental Health), framing, electrical (state L&I), plumbing, mechanical, insulation, drywall, gas, final. Inspectors travel from Coupeville so requests must be made at least 48 hours in advance. - Final and Certificate of Occupancy (~14d)
Final building inspection and septic system final triggers CO. Island County Assessor parcel record updated for property tax reassessment; new address assigned by Island County Public Works.
Viability (permitted uses)
- Long-term rental: yes Long-term rental of ADU explicitly permitted; Washington owner-occupancy preemption (where applicable) makes ADU eligible for full landlord-tenant treatment.
- Short-term rental: with-restrictions STR rules vary by city. Clinton regulates STRs separately from ADU permitting; check local STR ordinance and HOA covenants.
- Office rental: with-restrictions Detached office rental requires home occupation permit or rezoning.
- Home office: yes Home occupation permitted with restrictions on signage and customer traffic.
- Studio / workshop: yes Personal artist studio is a permitted accessory use.
- Agriculture: with-restrictions Limited urban agriculture permitted in residential zones; livestock varies by district.
- Relative support: yes Family-occupancy ADU explicitly permitted in single-family zones.
Contacts
Staff: Whidbey Building Permit Counter (South Whidbey/Clinton intake), Camano Island Building Office (Camano-side intake (alternative)), Island County Environmental Health (septic and well) (On-Site Sewage System review), South Whidbey Fire / EMS (Fire Marshal review (Clinton service area))
Utilities
- Water: Clinton Water Utility · 21d connect · $4,500
- Sewer: Clinton Sewer / Wastewater · 21d connect · $5,500
- Electric: Clinton Electric Utility · 14d connect · $1,800
- Gas: Clinton Gas Utility · 21d connect · $1,500
Property values & taxes
Construction timeline
Realistic total: best 7mo · typical 11mo · worst 17mo
Financing
State ADU loans:
Insurance impact
HOA prevalence & preemption
Washington enacted HOA preemption of ADU bans in Substitute House Bill 1337 (2023), which amended the Washington Uniform Common Interest Ownership Act and the Washington Horizontal Property Regimes Act to prohibit common-interest communities from banning ADUs on lots in GMA-planning jurisdictions. A homeowners' association may impose reasonable aesthetic or architectural standards, but may not categorically prohibit ADUs.
Regulatory overlays (1)
- seismic-zone
Seismic Design Category D1 per ASCE 7; soft-story and unreinforced-masonry seismic considerations may apply.
Technical envelope (climate & building code)
Climate & energy code
Building code
Amendments:
- Amendment
- Amendment
Legal history (timeline)
Current ordinance: Island County Code Title 17 (Zoning) - Accessory Dwelling Unit provisions; Clinton parcels governed by ICC chapters covering Rural and Rural Residential designations, adopted 1995-07-01, last amended 2024-12-10
- 1995-07-01 — Island County Code Title 17 (Zoning) - original ADU/guest-cottage provisions (county-ordinance)
Clinton is an unincorporated CDP on south Whidbey Island; Island County zoning under ICC Title 17 governs. Original code permitted one ADU per single-family lot in the Rural and Rural Residential designations.
Effect: Established baseline for Whidbey accessory dwelling permitting through Island County's Department of Planning and Community Development - the city of Clinton has never incorporated. - 2017-09-19 — Island County Comprehensive Plan 2036 update (county-ordinance)
Comprehensive plan revision that retained Rural Center designation for Clinton corridor and adjusted ADU density credit treatment for septic-served parcels.
Effect: Confirmed Clinton as a Rural Activity Center under Growth Management Act planning while keeping the one-ADU-per-lot limit on septic-served rural lots. - 2023-05-08 — Washington EHB 1337 (RCW 36.70A.681) - statewide ADU enabling (state-law)
Statewide preemption requiring two ADUs per lot in single-family zones within Urban Growth Areas. Clinton, being outside any UGA, is NOT subject to the EHB 1337 mandate; rural-Whidbey lots remain governed by Island County's local code.
Effect: Did not change Clinton ADU rules. The Whidbey CDP is rural, septic-dependent, and outside Oak Harbor / Langley UGAs - so EHB 1337 preemption does not reach these parcels. One ADU per lot remains the local norm. - 2024-12-10 — Island County BOCC - 2024 ADU code update (county-ordinance)
Board of County Commissioners adopted code revisions clarifying detached-ADU size cap at 1000 sqft countywide and removing owner-occupancy condition for non-rural-Whidbey UGA parcels.
Effect: Aligned Island County ADU code with state mandate for UGA portions while preserving rural lot restrictions; Clinton parcels (rural) keep septic-driven size and density constraints but no longer have owner-occupancy requirement.
Washington state — ADU law and programs
State ADU law
Washington preempts local ADU regulation in urban growth areas of cities and counties subject to the Growth Management Act through Engrossed Second Substitute House Bill 1337 (2023), codified principally at RCW 36.70A.680-.681. Cities and counties planning under the GMA must allow at least two ADUs per lot in urban growth areas, must not require owner-occupancy, must not impose minimum-lot-size or setback rules stricter than those for the primary residence, and must allow ADUs to be sold separately as condominiums. Related House Bill 1110 (2023), codified at RCW 36.70A.635, requires 'middle housing' (duplexes, triplexes, fourplexes) in most residential zones of large cities.
- RCW 36.70A.680 — Accessory dwelling units — Requirements for cities and counties planning under this chapter — Sets the minimum entitlement floor for ADUs in GMA-planning jurisdictions: at least two ADUs per lot in urban growth areas, no owner-occupancy requirement, no stricter setback or lot-coverage rules than for the primary residence, no parking requirements within a half-mile of major transit stops, and no prohibition on selling an ADU separately as a condominium.
- RCW 36.70A.681 — Accessory dwelling units — Design, size, and aesthetic standards — Caps what local governments may require in ADU design and size standards. Maximum ADU size must be at least 1,000 square feet in most zones. Street-facing facades and aesthetic review may not be used to categorically prohibit ADUs.
- RCW 36.70A.696 — Accessory dwelling units — Definitions — Statutory definitions of 'accessory dwelling unit,' 'attached accessory dwelling unit,' 'detached accessory dwelling unit,' 'owner,' and 'urban growth area' used by RCW 36.70A.680-.681.
- RCW 36.70A.635 — Middle housing — Cities planning under this chapter — HB 1110 (2023). Requires cities over specified population thresholds to allow duplexes, triplexes, fourplexes, townhouses, cottage housing, and stacked flats in most residential zones. Interacts with ADU law because ADUs and middle housing both contribute to the state's response to the GMA's housing element.
State HOA preemption
Washington enacted HOA preemption of ADU bans in Substitute House Bill 1337 (2023), which amended the Washington Uniform Common Interest Ownership Act and the Washington Horizontal Property Regimes Act to prohibit common-interest communities from banning ADUs on lots in GMA-planning jurisdictions. A homeowners' association may impose reasonable aesthetic or architectural standards, but may not categorically prohibit ADUs.
- RCW 64.38.057 — Homeowners' associations — Accessory dwelling units — Prohibits a homeowners' association governing a plat within a GMA-planning city or county from recording or enforcing a provision that prohibits the construction, use, or rental of an accessory dwelling unit on a lot. Reasonable design guidelines consistent with RCW 36.70A.681 remain enforceable.
State financing programs
The Washington State Housing Finance Commission (WSHFC) administers state-level housing finance programs. Washington does not currently operate an ADU-specific statewide grant or forgivable-loan program comparable to California's CalHFA ADU Grant, but several state programs can be used for ADU construction when program criteria are met.
State housing programs
Washington supports ADU implementation through Department of Commerce technical assistance and grant programs rather than through a single statewide pre-approved-plan catalog. The state provides model ADU code under the GMA, distributes GMA update grants to help jurisdictions comply with RCW 36.70A.680-.681, and has produced ADU guidance documents for local governments.
Federal (United States) — ADU-relevant rules and programs
Federal ADU law
The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.
Federal financing programs
Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.
Federal tax credits
There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.
Federal housing programs
HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.
ZIP Code
- 98236
Post Office
- 4801 Deer Lake Rd, 98236