Planning commission begins first review of detached accessory dwelling unit ordinance ahead of Oct. 1 state deadline

Centerville planning staff opened a first review of a draft detached accessory dwelling unit (DADU) ordinance designed to bring the city into compliance with state law that becomes effective Oct. 1, 2026.

Staff framed the draft as a work-in-progress and asked commissioners to review the provided material over the next two weeks so the commission could refine the language and schedule a public hearing. The presentation walked commissioners through state-code references, model language from other nearby cities and policy choices the city must make on parking, meters, setbacks, conversions and rental limits.

“Basically, it’s our deadline,” the staff member said, noting the state code sections he referenced and explaining that the city must adopt a local land-use regulation for detached ADUs to remain compliant when the state standard takes effect. He told commissioners he used Mill Creek’s code as a middle-ground model and pulled relevant internal-ADU language where appropriate.

Key points flagged by staff for commissioner guidance included:

- Lot-size baseline: the state’s benchmark was described as 11,000 square feet as the floor many cities used; staff said cities cannot set a minimum larger than the state cap for certain elements and asked commissioners whether to mirror that benchmark.

- Parking: state guidance allows one on-site parking space if a DADU is under 650 square feet and two spaces if 650 square feet or larger. Staff noted questions about permitting tandem parking and how to accommodate on-site circulation.

- Utilities and meters: public-works staff recommended a separate water meter and dedicated water line for the DADU and separate sewer-accounting to avoid capacity and billing issues.

- Setbacks and conversions: state code requires allowing conversion of existing accessory buildings to DADUs; staff warned this complicates setback rules and could create grandfathered situations where neighboring parcels are treated differently.

- Short-term rentals and owner-occupancy: the draft includes a 90-consecutive-day minimum rental requirement to prohibit short-term stays (e.g., Airbnb) and contemplates owner-occupancy rules consistent with accessory-dwelling practice.

Staff said the commission should expect two to three commission meetings for review and then council review and asked commissioners to email additional examples of other cities’ DADU ordinances for consideration. Commissioners asked clarifying questions but primarily deferred detailed drafting to a future meeting and a public hearing schedule.

Next steps: commissioners will review the draft and related materials, provide written comments to staff, and the commission will aim to refine the draft and set a public hearing date during follow-up meetings.