O'Fallon Zoning & Land Use Guide
Official references and local checks
Use the official references below to identify the rules that apply to your address, then confirm parcel-specific requirements with the local authority before filing an application.
Official references
- Population:
- 91,316
- County:
- St. Charles County
- State building code:
- No mandatory statewide building code; local adoption(statewide default)
- State ADU law:
- No statewide override; local rules apply
- FEMA flood map:
- Search flood zones
- Planning department:
- O'Fallon Community Development
- Municipal code:
- View code online
Before you apply
- Call the O'Fallon Community Development: (636) 379-5520
- Search the municipal code for the chapter that covers your zoning district and proposed use.
- Check FEMA flood zone for your parcel — flood-zone status changes setbacks, foundation requirements, and insurance.
- Check your HOA CC&Rs and recorded deed restrictions — they are common in O'Fallon and frequently restrict ADUs, fences, and exterior changes beyond what zoning allows.
Key Zoning Facts
O'Fallon is a city of approximately 91,316 residents (2020 Census) in St. Charles County, Missouri. The city manages land use and development through its local zoning ordinance, administered by O'Fallon Community Development. The zoning code divides the municipality into districts that regulate the types of uses permitted, building heights, lot sizes, setbacks, and density.
O'Fallon uses residential zoning districts from R-1 (Single-Family Estate) through R-4 (Multi-Family Residential), along with commercial districts (C-1 Neighborhood Commercial, C-2 General Commercial, and C-3 Highway Commercial) and a Light Industrial (M-1) district. Each district has specific dimensional standards governing minimum lot sizes, setbacks, and maximum building heights.
Key Residential Zoning Districts
The primary residential districts in O'Fallon include:
- R-1 (Single-Family Estate) — Requires a minimum lot size of 20,000 square feet with a 40-foot front setback, 12-foot side setbacks, and a 30-foot rear setback. Maximum building height is 35 feet.
- R-2 (Single-Family) — Requires a minimum lot size of 12,000 square feet with a 30-foot front setback, 8-foot side setbacks, and a 25-foot rear setback. Maximum building height is 35 feet.
- R-3 (Single-Family) — Requires a minimum lot size of 8,000 square feet with a 25-foot front setback, 7-foot side setbacks, and a 25-foot rear setback. Maximum building height is 35 feet.
- R-4 (Multi-Family) — Allows multi-family housing on lots of at least 6,000 square feet with a 25-foot front setback, 10-foot side setbacks, and a 25-foot rear setback. Maximum building height is 45 feet.
ADU Rules
O'Fallon does not appear to have a specific ADU (Accessory Dwelling Unit) ordinance. Missouri has no statewide ADU mandate. Property owners interested in building an accessory dwelling unit should contact O'Fallon Community Development to verify whether such structures are permitted under current zoning regulations.
Development Process
Development in O'Fallon generally requires obtaining the appropriate permits from the city's community development department. The process typically involves:
- Zoning Verification — Confirm that your proposed use is permitted in the applicable zoning district
- Site Plan Review — For commercial and multi-family projects, submit a site plan for review
- Building Permit — Apply for a building permit with construction documents
- Inspections — Schedule required inspections during construction
- Certificate of Occupancy — Obtain final approval before occupying the structure
For projects that do not conform to existing zoning, property owners may need to seek a variance, special exception, or rezoning through the local board of zoning appeals or planning commission.
Key Considerations
Before starting any development project in O'Fallon, property owners should:
- Verify the zoning classification of their property
- Review setback, height, and lot coverage requirements for the applicable district
- Check for any overlay districts or special regulations
- Determine if the property is in a flood zone using FEMA's flood map service
- Confirm whether HOA covenants or deed restrictions apply
- Contact O'Fallon Community Development at (636) 379-5520 for pre-application guidance
Disclaimer: This guide provides general information about zoning in O'Fallon and should not be relied upon as legal advice. Zoning codes are subject to change. Always verify current regulations with O'Fallon Community Development or the municipal code before making development decisions.
Regulatory Layers That Apply in O'Fallon
Your property is subject to ALL of these regulatory layers. Each one can impose additional requirements beyond the others.
Federal
- FEMA flood mapping: check parcel-specific flood-zone status
- View FEMA Flood Map
State — Missouri
- Building Code: IBC/IRC (locally adopted with amendments)
County — St. Charles County
City / Municipal
The municipality's zoning ordinance, building-code enforcement, and local permits form the primary local layer of land-use regulation for your property.
Overlay Districts
No overlay districts identified.
Private Restrictions
- Private covenants, deed restrictions, condominium rules, or association rules can impose requirements beyond zoning.
- Check HOA CC&Rs and deed restrictions for additional requirements.
Statewide Context (Missouri)
Local data for O'Fallon is limited. The following state-level facts apply across Missouri and are inherited by this page until city-specific details are verified.
- State Building Code
- No mandatory statewide building code; local adoption
- State ADU Preemption
- No statewide override
- Coastal Zone
- No
- Wildfire Zones
- No
Permit Costs & Timelines
Check Current Permit Fees & Timelines
Permit fees and review times can vary by project type, scope, valuation, and required approvals. Check the current schedule with the local permitting authority before filing.
Check current O'Fallon permit information →Official Sources
City-specific