Jefferson County, MO Accessory Structures: Shed & Carport Rules (2026)
Shed permit rules in Jefferson County, MO, also referred to as storage shed, backyard shed, or accessory building regulations, set size limits, setbacks, and when a building permit is required.
Key Facts
- Max size, RA-5/LR-2 lots
- 4,000 sq ft combined or 5% of lot
- Max size, R-40/R-20/R-10/R-7 lots
- 1,200 sq ft combined or 5% of lot
- Small shed setback
- 200 sq ft or less: 15 ft from rear line
- Max height
- 35 feet (§400.2770)
- Corner lot setback
- 15 feet from side property line
- Governing sections
- UDO §400.2870, cross-ref §400.2770
Summary
Jefferson County caps combined accessory-building square footage by district under UDO Section 400.2870: up to 4,000 square feet (or 5% of the yard) on RA-5 and LR-2 lots, 1,200 square feet on R-40 through R-7 lots. A shed of 200 square feet or less needs only a 15-foot rear setback.
In the "RA-5" Rural/Agricultural and "LR-2" Large Lot Residential Districts, there shall be permitted accessory buildings, combined square footage of which shall not exceed a total of four thousand (4,000) square feet or five percent (5%) of the lot area that is not occupied by the primary use, whichever is most permissive. Accessory buildings shall comply with Section 400.2770... In the "R-40", "R-20", "R-10" and "R-7" residential zoning districts, accessory buildings shall not exceed a total of twelve hundred (1,200) square feet or five percent (5%) of the lot area that is not occupied by the primary use, whichever is most permissive... Accessory buildings that are two hundred (200) square feet or less shall be set back at least fifteen (15) feet from the rear property line.
Full Breakdown
A shed or other detached accessory building in unincorporated Jefferson County is capped by total square footage, not a single-building limit. 2870 sets that ceiling by district: up to 4,000 square feet combined, or 5% of the lot area not covered by the house, whichever is more generous, on "RA-5" Rural/Agricultural and "LR-2" Large Lot Residential parcels; and up to 1,200 square feet combined, or the same 5% test, on "R-40," "R-20," "R-10" and "R-7" lots. If no house has been built yet, those same caps apply to the total accessory square footage on the lot.
A small shed of 200 square feet or less needs only a 15-foot setback from the rear property line. 2770: they cannot sit in front of the principal house, must observe the same minimum side setback required for the house itself, cannot exceed 35 feet in height, and on a corner lot must sit behind the primary structure and at least 15 feet off the side property line. 430. 2770(A)(3).
Violations & Fines
Building an accessory structure that exceeds the district's square-footage cap, skips the required setback, or is erected without the building permit and site plan Section 400.2770 requires is a UDO violation under Section 400.140. County Code Enforcement can order correction; noncompliance is a misdemeanor carrying up to a $1,000 fine, up to one year in jail, or both, with each day a separate offense.
Frequently Asked Questions
How big of a shed can I build in Jefferson County?
Do I need a permit for a small backyard shed?
Can I put my shed in the front yard?
Sources & Official References
Other rules in Jefferson County
How Jefferson County compares: Shed Permit Requirements by City·Compare Jefferson County to another location·View the Missouri accessory structures overview
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