Horace

Cass County sits in North Dakota, which has not enacted a statewide ADU preemption or by-right ADU statute. Authority over ADU zoning, setbacks, parking, size limits, owner-occupancy, and permitting therefore rests with the local jurisdiction. The county adopts its own zoning ordinance for unincorporated territory, and each incorporated municipality inside the county adopts its own.

State-floor overlay: No North Dakota statewide ADU preemption is in force as of 2026-04-27. The county and its incorporated municipalities retain full authority over ADU zoning and permitting.

Cass County administers flood-hazard, and (where mapped) coastal, wildland-fire, historic, and airport overlays that shape ADU project feasibility. The most consistent overlay across the county is FEMA NFIP floodplain regulation; other overlays apply to specific geographies inside the county.

• FEMA NFIP Special Flood Hazard Areas in Cass County — A new ADU in a mapped SFHA must be elevated to or above the Base Flood Elevation; cost impact on the project is often material.
• Historic districts and individually-listed historic resources

Cass County issues building permits for parcels in unincorporated territory through its development services / planning department, with separate review tracks for zoning conformance, building-code compliance, on-site sewage where applicable, floodplain compliance, and addressing. Inside incorporated municipalities, city departments handle their own permits; the county's authority is geographically limited to unincorporated territory. An ADU permit application is typically processed as a residential building permit with a zoning verification step against the county's ordinance for the parcel's zoning district.