St. Louis County, MO Building Setbacks & Zoning: Setback Rules (2026)
Key Facts
- R-1 front setback
- 30 ft from roadway right-of-way
- R-1 side/rear setback
- 15 ft from property line
- R-6A front setback
- 20 ft from roadway right-of-way
- R-6A side setback (house)
- 5 ft, 3 ft for garage
- Corner lot sight triangle
- 3 ft max obstruction height
- Fence/wall exception
- Up to 6 ft inside any setback
- Setback averaging range
- Floor 15 ft, ceiling 50 ft
Summary
Structure setbacks in unincorporated St. Louis County shrink as zoning density rises. The county's largest-lot residential district, R-1, holds buildings 30 feet off any road right-of-way and 15 feet off side or rear lines, while the denser R-6A district cuts those minimums to 20 feet in front and as little as 5 feet on the side for single-family homes.
(3)Minimum structure setback requirements: General.(a)Front structure setbacks. No structure shall be allowed within thirty (30) feet of any roadway right-of-way line.(b)Side and rear structure setback. No structure shall be allowed within fifteen (15) feet of any property line other than a roadway right-of-way line.(4)Specific structure setback regulations and exceptions.(a)Notwithstanding any other provision of this chapter, on corner lots, no structure or plant material exceeding three (3) feet in height above the elevation of the street pavement is allowed within the sight distance triangle.(b)Boundary walls or fences, six (6) feet or less in height, are allowed within the minimum structure setback requirements.(c)Permitted information signs, six (6) feet or less in height, are allowed within the minimum front structure setback.(d)Permitted directional signs, three (3) feet or less in height, are allowed within the minimum front structure setback.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 85 | Traffic: Supplement 80).
Full Breakdown
7 sets the baseline: in the "R-1" Residence District no structure may sit within thirty (30) feet of a roadway right-of-way line, and no structure may sit within fifteen (15) feet of any other property line. 7) relaxes this to a twenty-foot front setback, a five-foot side setback for single-family homes (three feet for a detached garage, ten feet for other structures), and a fifteen-foot rear setback, showing the pattern across the county's residence districts: setbacks fall as the district's permitted density rises. Several exceptions apply on top of the base numbers.
Corner lots must keep a sight-distance triangle clear of anything over three feet tall. Boundary walls and fences up to six feet, information signs up to six feet, and directional signs up to three feet may all sit inside the required front setback. 7(1)(b). 7(4)(j) lets a lot use the average setback of nearby homes when more than half the dwellings within 500 feet vary by no more than ten feet, though the result can never be closer than 15 feet or farther than 50 feet from the right-of-way. Solar arrays face their own 20-foot property-line setback and a footprint cap tied to the principal structure.
Violations & Fines
Building past the applicable front, side, or rear line blocks issuance of a building permit and can trigger a stop-work order on a structure already under construction. The Department of Planning reviews site plans against the district's specific setback table before issuing permits, and an owner who needs relief from the standard must apply for a variance through the Board of Zoning Adjustment; encroaching structures can be ordered removed or altered at the owner's expense.
Frequently Asked Questions
How close to the street can I build in unincorporated St. Louis County?
Do side and rear setbacks change between residential zoning districts?
Can a fence sit inside my required yard setback?
Sources & Official References
Other rules in St. Louis County
Compare St. Louis County to another location·View the Missouri building setbacks & zoning overview
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