ADU Rules in Williston, North Dakota

Williston is the county seat of Williams County, located in the far northwestern corner of North Dakota near the confluence of the Missouri and Yellowstone rivers. It is the commercial hub of the Bakken/Three Forks shale oil formation — one of the most productive oil fields in North America.

The Bakken Boom and Housing Legacy

The Bakken oil boom, which accelerated roughly between 2008 and 2014, transformed Williston from a small agricultural and oil-service city into one of the fastest-growing cities in the United States. At its peak:

• Williston's population roughly doubled in a few years
• Rents and home prices surged to levels rivaling major coastal cities
• Housing was so scarce that workers lived in cars, RVs, and temporary "man camp" dormitories
• The city's infrastructure (roads, water, sewer, schools) struggled to keep pace

Since the boom moderated following the 2014–2016 oil price collapse, Williston has worked to absorb the housing built during the rush and to stabilize its residential development landscape. Oil production continues at meaningful levels, keeping Williston an active oil city, but the extreme growth pace has slowed. This history is relevant context for current ADU and housing policy — Williston has strong motivation to enable flexible housing and infill development.

No Statewide ADU Law — Local Zoning Controls

North Dakota has not passed statewide ADU preemption legislation. All ADU rules in Williston are established exclusively by the City of Williston Zoning Ordinance. There is no state mandate requiring the city to allow ADUs or restricting local regulatory authority.

ADU Types Potentially Allowed

Williston's zoning code may permit ADUs in various residential districts, including:

• Detached ADUs — standalone accessory structures on the same residential lot
• Attached ADUs — additions to the primary dwelling sharing a common wall
• Garage conversions — converting an existing garage into habitable living space
• Basement/interior ADUs — a self-contained unit within the existing structure

Given the volume of housing constructed during the boom years (including manufactured homes, modular units, and quickly built structures), zoning standards may address conversion of non-traditional housing forms. Confirm current allowances with the Planning and Zoning Department.

Typical Development Standards

ADUs in Williston are generally subject to:

• Minimum lot size — a minimum lot area required before an ADU is permitted
• Maximum ADU size — typically capped as a percentage of the primary structure or an absolute limit (e.g., 800–1,000 sq ft)
• Setbacks — rear and side yard setback requirements apply; detached rear ADUs typically require at least 5 feet from property lines
• Height limits — detached ADUs generally limited to one story or the accessory structure height limit in the applicable zone
• Parking — one additional off-street parking space may be required for the ADU
• Utility connections — separate or shared metering per city utility requirements

All specific standards should be verified with the Williston Planning and Zoning Department, as the zoning code may have been updated in response to post-boom planning efforts.

Missouri River and Flood Zone Considerations

Williston is near the confluence of the Missouri and Yellowstone rivers. Lake Sakakawea (created by Garrison Dam) is to the east. FEMA flood zone designations apply to areas within river floodplains. Properties near the Missouri River or its tributaries should verify their flood zone status. ADU construction in a Special Flood Hazard Area (SFHA) requires a floodplain development permit and must meet Base Flood Elevation (BFE) requirements.

Extreme Climate Requirements

Williston lies in one of the coldest and most exposed parts of North Dakota. Winter temperatures can reach −30°F to −40°F with wind chill making conditions even more extreme. All construction must meet North Dakota building code requirements for:

• Foundation depth: Footings well below the frost line (42–60+ inches)
• Insulation: High R-values for walls, roofs, and foundation assemblies
• Mechanical systems: Heating systems adequately sized for extreme cold, with attention to freeze protection for all plumbing

Permit Process

1. Confirm your property's zoning district and ADU eligibility with the Planning and Zoning Department
2. Check flood zone status for your parcel (FEMA FIRMs)
3. Obtain any required zoning approvals or conditional use permits
4. Submit a building permit application with complete construction drawings
5. Complete all required inspections

Contact Information

City of Williston Planning and Zoning Department

• Website: willistonnd.gov/departments/planning_and_zoning
• Address: City Hall, 212 Main Street, Williston, ND 58801
• Phone: (701) 577-8100

Disclaimer: Zoning regulations change frequently. The information on this page is provided for general informational purposes only and may not reflect the most current rules. Always verify ADU requirements directly with the City of Williston Planning and Zoning Department and consult a licensed architect or contractor before beginning any project.