O'Fallon, MO Building Setbacks & Zoning: Structure Height Limits (2026)
Key Facts
- R-1 dwelling height cap
- 2.5 stories / 35 feet
- R-1 accessory building cap
- 25 feet
- Accessory height rule
- never taller than main house
- Commercial max with approval
- 6 stories
- First zoning fine
- up to $200
Summary
O'Fallon caps single-family homes in the R-1 District at two and one-half (2 1/2) stories or thirty-five (35) feet under City Code § 400.080(D)(5). Detached accessory buildings are capped lower still, at twenty-five (25) feet, and can never be taller than the main house.
5. Height Requirements. a. For Buildings And Structures. No building or structure shall exceed a height of two and one-half (2 1/2) stories, or thirty-five (35) feet. b. For Accessory Buildings. No detached accessory building shall be higher than twenty-five (25) feet, nor higher than the main building.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4860992; v58 updated 2026-05-14; through 05-14-2026).
Full Breakdown
Section 400.080(D)(5) sets the height ceiling for O'Fallon's largest residential zoning category, the "R-1" Single-Family Residential District: "No building or structure shall exceed a height of two and one-half (2 1/2) stories, or thirty-five (35) feet," and no "detached accessory building shall be higher than twenty-five (25) feet, nor higher than the main building." The same 2 1/2-story/35-foot cap for dwellings carries into the "R-1A" Single-Family Suburban Residential District under § 400.085, where accessory buildings are likewise limited to twenty-five (25) feet and cannot exceed the height of the main structure.
Other districts scale up: the "AG" Agricultural District allows dwellings up to 2 1/2 stories but permits farm buildings to reach fifty (50) feet under § 400.155(D)(5), while commercial districts such as "C-2" General Business and "C-3" Highway Commercial cap most buildings at fifty (50) feet or three (3) stories, with the Planning and Zoning Commission able to approve up to six (6) stories under § 400.125(D)(5) if the added height will not interfere with St. Charles County's emergency microwave communications system and the local fire district can still provide protection.
For a homeowner building a house or detached garage in the City's core single-family districts, however, the operative ceiling is the R-1 standard: 35 feet for the house, 25 feet for any detached accessory structure, and the accessory structure can never out-top the house itself.
Violations & Fines
Exceeding the height limit in Chapter 400 is a zoning violation subject to the City's general penalty at § 100.010(A)(4): under the RSMo §§ 89.120/89.490 zoning schedule, a first violation within twelve months draws a fine up to $200, rising to $275, $350 and $450 for the second, third and fourth-plus violations, and the City can require the excess height to be removed.
Frequently Asked Questions
How tall can I build a house in O'Fallon's R-1 District?
How tall can my detached garage or shed be?
Can buildings ever go taller than 35 feet in O'Fallon?
Sources & Official References
Other rules in O'Fallon
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