Chelan County, WA Accessory Structures: ADU Rules (2026)
ADU rules in Chelan County, WA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- ADUs per lot
- One, with a single-family home or duplex
- Max floor area
- 1,200 sq ft (garages/decks excluded)
- Parking
- One additional off-street space required
- RV as ADU
- Never permitted
- Density treatment
- ADUs don't count toward zoning density
- Owner-occupancy
- Required only for short-term rental use
Summary
Unincorporated Chelan County allows one accessory dwelling unit per lot with a single-family home or duplex, capped at 1,200 square feet of floor area, under Chelan County Code Section 11.88.200. An ADU needs its own extra parking space, cannot be a recreational vehicle, and doesn't count toward the zone's density calculation.
§ 11.88.200. Accessory dwelling unit. ... Accessory dwelling units shall meet the following criteria: (1) There shall be no more than one accessory dwelling unit per lot in conjunction with a single-family dwelling unit, or duplex. (2) An accessory dwelling unit may be attached to, created within, or detached from a new or existing single-family dwelling unit. ... (4) The floor area of the accessory dwelling unit may be attached to, created within, or detached from a new or existing single-family dwelling unit or duplex; provided, that the floor area of an accessory dwelling shall not exceed one thousand two hundred square feet. Excluded from the calculation of the allowed floor area are the following: garages, and any space subservient to the primary garage use (e.g., storage, mechanical, bathroom, utility room), carports, stairwells and covered/uncovered decks and patios. ... (6) No recreational vehicle shall be considered an accessory dwelling unit.
Full Breakdown
200 of the Chelan County Code sets the standards for accessory dwelling units countywide. Only one ADU is allowed per lot, and only in conjunction with a single-family dwelling or a duplex; the unit can be attached to, built within, or fully detached from the primary structure. Its floor area is capped at 1,200 square feet, but the code excludes garages and space subservient to a garage (storage, mechanical, bathroom, utility rooms), carports, stairwells, and covered or uncovered decks and patios from that count, so those features do not eat into the 1,200-square-foot allowance.
290, which triggers additional parking requirements. No recreational vehicle can ever be counted as an accessory dwelling unit. Wherever practical, the ADU and the primary home are required to share a single common driveway rather than each cutting its own access. 200(8) exempts ADUs from density calculations entirely, so adding one does not use up a lot's allowed unit count under Title 11's zoning tables. 290; a standard long-term-rental ADU carries no owner-occupancy requirement.
Violations & Fines
Building an ADU larger than 1,200 square feet, adding a second ADU on a lot, or converting an RV into a dwelling unit without complying with Section 11.88.200 is a zoning violation. Community Development can issue a notice and order under Chapter 16.06, and failing to correct the violation within the deadline it sets brings a $750 civil fine for a first violation and $1,500 for a repeat violation under Chapter 16.16.
Frequently Asked Questions
How big can an ADU be in unincorporated Chelan County?
Can I use an RV as an accessory dwelling unit?
Do I have to live on the property if I build an ADU?
Does an ADU count against my lot's zoning density?
Sources & Official References
Other rules in Chelan County
How Chelan County compares: Easiest Cities to Build an ADU·Compare Chelan 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.