Accessory Structures in Florissant, MO: What Residents Actually Need to Know

If you live in Florissant or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. Florissant has 2 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.

ADU Rules

Missouri has no statewide ADU mandate. Florissant's Zoning Code (Chapter 405) does not authorize accessory dwelling units in single-family R-1 through R-4 districts. Section 405.085 limits R-1 to single-family dwellings plus customary accessory buildings. A duplex requires R-5 zoning.

Key details: State ADU Law: None (no Missouri preemption). City Zoning Code: Chapter 405 (Title IV). State Enabling Statute: RSMo Chapter 89. R-1 Permitted Use: Single-family dwellings only. Duplex Zone Required: R-5 Duplex District.

Constructing a separate dwelling unit on a single-family-zoned lot without rezoning violates Florissant's Zoning Code. Building without a permit violates the adopted residential code. Code enforcement may issue stop-work orders, citations, and fines, or require removal.

Compared to other cities, Florissant takes a harder line on adu rules. The enforcement and penalty structure reflects that.

Shed Rules

Florissant treats sheds and storage buildings as accessory structures under the Zoning Code (Chapter 405) supplementary district regulations and the Building Code (Chapter 500). The published Public Works guideline caps shed height at 18 feet, and not exceeding the height of the residence; structures within 6 feet of the house must match the house setback, and any shed of 200 square feet or more requires construction plans submitted with the building permit application.

Key details: Permit Required: Yes - Public Works. Max Height: 18 ft / not over residence. Setback Rule: Match house if within 6 ft. Plan Review: 7-10 days. Plans Required: 200 sq ft and over.

Building a shed without a Chapter 500 building permit, or placing one in violation of the 18-foot height cap, the rule that the shed cannot exceed the residence's height, or the applicable zoning-district setbacks, exposes the owner to enforcement under Article XII (Property Maintenance Code) and the city's general penalty schedule. The Department of Public Works can issue stop-work orders, require removal or after-the-fact permitting, and refer continuing violations to Florissant Municipal Court.

The Bottom Line

Florissant's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Florissant is broadly strict or permissive.

All of the above reflects Florissant's municipal code as of our last review. If you need specifics on fines, exemptions, or filing requirements, the detailed ordinance pages linked above have the full breakdown.