Building permits, zoning and land rules in Jefferson County, Missouri

At a glance

Building permit

Required for regulated work in unincorporated Jefferson County; applications undergo plan review¹⁸

Building code

2015 International Residential Code plus county amendments (Chapter 500)⁹

Zoning

Yes: the Unified Development Order regulates development in unincorporated areas¹⁰¹¹

Septic permits

Required for new and replacement systems through Jefferson County Code Enforcement⁷⁵

Septic soils

Only 2.3% of the county's soils are free of severe limits for a conventional drain field¹²

Small sheds

No building permit for a one-story detached storage shed up to 200 sq ft¹³

Driveways

County permit on county right-of-way; MoDOT permit on state right-of-way¹⁴¹⁵

RV or tiny home living

Not confirmed; ask the Planning Division what your zoning district allows¹⁶

Who to call

Contact details are copied from each office’s official page and were checked against it on September 29, 2026.

Do you need a building permit in Jefferson County, Missouri?

Yes. Unincorporated Jefferson County, Missouri requires a permit before a regulated building or structure is erected¹. Jefferson County has adopted a local building code, and Code Enforcement regulates construction, alteration and occupancy in unincorporated areas²⁶. The adopted standards include the 2015 International Residential Code and local amendments in Chapter 500⁹. Applications and plans receive detailed review before a permit is issued⁸.

Some small projects are exempt. A one-story detached storage shed no larger than 200 square feet, a fence no higher than 8 feet and a grade-supported water tank within the county's stated limits do not need a building permit¹³. County-regulated construction proceeds through staged inspections, including foundation, framing, rough-in and final inspection, with additional inspections possible¹⁷. Ask Code Enforcement before treating a barn, workshop or other accessory structure as exempt.

Who is the Jefferson County building department, and how do you reach them?

The Jefferson County building department is the Code Enforcement Division at 725 Maple Street in Hillsboro, phone 636-797-5310, open Monday through Friday from 7:30 am to 5 pm⁶. The county's Citizen Portal accepts building-permit applications and inspection requests⁶. Residential applications go through plan review and may require address verification, a site plan, construction drawings, contractor details, sewer documentation, and driveway or floodplain approval when applicable⁸.

Jefferson County's fee schedule bases permit charges on construction cost and lists a separate residential plan-review charge¹⁸. The permit form requires contractor verification for the homeowner or general contractor and the applicable licensed trades¹⁹. Building inspections should be requested at least one business day ahead, and incomplete work can trigger a re-inspection fee¹⁷. The county has not confirmed a separate owner-builder exemption, so ask Code Enforcement what work an owner may personally perform²⁰⁶.

Does Jefferson County, Missouri have zoning?

Yes. Jefferson County applies its Unified Development Order and zoning districts in unincorporated areas; incorporated municipalities may administer different rules³¹⁰. The Unified Development Order was adopted in 2008 and has since been amended¹¹. Every unincorporated parcel is subject to property-line setbacks based on its zoning district and lot shape⁴.

The Jefferson County Planning Division takes applications for zone changes, conditional uses, variances, plats and development plans through the Citizen Portal¹⁶. Preliminary subdivision plats require a completed checklist and a hearing before the Planning and Zoning Commission²¹. The available material does not confirm current minimum lot sizes, minimum home sizes, lot coverage or height limits, so give Planning the parcel number and proposed use before relying on a listing. The county is also rewriting the Unified Development Ordinance to conform to its newer master plan²².

How do septic permits work in Jefferson County?

Jefferson County Code Enforcement administers onsite sewage permits and inspections in unincorporated Jefferson County⁷. New and replacement systems require a permit; a licensed onsite septic contractor must sign the application, and new systems need a soil morphology report, engineered sewer drawings and plan review⁵. The county's On-Site Sewage Treatment Code is Chapter 705⁹.

Septic work has required field-preparation, onsite, rough-in-before-backfill and final inspections, and every permit must receive a final inspection²³. Only 2.3% of Jefferson County soils are rated free of severe limitations for a conventional drain field, so establish system feasibility and cost before committing to a building site¹². Where public sewer serves the property, the residential checklist requires a sewer-district confirmation letter²⁴. For an existing system in a land purchase, Missouri local health agencies generally do not inspect for a transfer, so arrange a licensed private inspection²⁵.

Can you live in an RV or tiny home on your land in Jefferson County?

We could not confirm whether long-term RV occupancy or a tiny home is allowed on a particular Jefferson County parcel. Because unincorporated land is regulated by zoning districts and district-based setbacks, ask the Planning Division what the parcel's district permits before buying or moving a unit onto the land¹⁰⁴¹⁶. Minimum dwelling size and temporary-camping rules also remain unconfirmed.

A tiny home constructed as a dwelling is regulated building work and requires county review in unincorporated Jefferson County¹². The county's permit form says a structure cannot be occupied until the final inspection is approved¹⁹. An RV does not avoid wastewater rules: where onsite sewage is proposed, Jefferson County Code Enforcement administers the permit and inspection process⁷²³. Confirm zoning, sanitation and any temporary-use approval separately rather than assuming an RV or small footprint creates an exemption.

Building a home in Jefferson County: what are the steps, in order?

1. Ask the Planning Division to confirm the parcel's zoning district, allowed use and setbacks¹¹⁴.
2. Determine whether the site is in a special flood hazard area; proposed construction or other development there requires a separate floodplain development permit²⁶.
3. Establish sewer service or septic feasibility. A public-sewer connection may require a district letter, while a new septic system needs soils, engineered drawings and a licensed contractor²⁴⁵.
4. Obtain a county driveway permit for work on county right-of-way or a MoDOT permit for access on state right-of-way¹⁴¹⁵.
5. Submit the address verification, site plan, building plans, contractor information and related approvals for plan review⁸.
6. Schedule required building and septic inspections, including their final inspections, before occupancy¹⁷²³¹⁹.

What should you check before you buy land in Jefferson County?

Start with the exact zoning district, setbacks and legal-lot status; unincorporated parcels are subject to district controls, and subdividing land triggers plat review⁴²¹. Check access ownership too: a new driveway on county right-of-way requires a county permit, while access on state right-of-way goes through MoDOT¹⁴¹⁵. Construction or land development in a special flood hazard area needs separate county approval²⁶.

Resolve wastewater before selecting the house site because only 2.3% of Jefferson County soils are rated free of severe limitations for a conventional drain field¹². Terrain adds cost: 77.5% of the county is wooded, and 42.5% of its land has slopes of 15% or less²⁷²⁸. The effective property-tax rate is about 0.8%, and the median annual bill is $1,835²⁹³⁰.

Watch-outs

• Jefferson County adopted a new master plan on November 10, 2025 and is rewriting its zoning code (the Unified Development Ordinance) to match it, so confirm the current rules with the Planning Division before you rely on them²².
• Jefferson County Code Enforcement issues and inspects onsite sewage permits in unincorporated areas⁷²³.
• Construction and other development in a Jefferson County special flood hazard area require a separate floodplain development permit²⁶.
• A Jefferson County structure cannot be occupied until its final inspection is approved¹⁹.
• Whether an owner can do their own electrical, plumbing or septic work in Jefferson County is unconfirmed; the septic application requires a licensed on-site contractor, so ask Code Enforcement at 636-797-5310 about the trades²⁰³¹⁶.

Sources

1. Jefferson County MO - Building Permits (2026 county census)
2. Codes & Ordinances, quoted and re-checked
3. County Codes, quoted and re-checked
4. Development Review, quoted and re-checked
5. On-Site Sewage Treatment System Permit Application, quoted and re-checked
6. Jefferson County Code Enforcement Division (jeffcomo.gov)
7. Codes & Ordinances, quoted and re-checked
8. Residential Building Permit Application Checklist, quoted and re-checked
9. Jefferson County Code Enforcement Division (Codes & Ordinances) (jeffcomo.gov)
10. Development Review, quoted and re-checked
11. County Codes, quoted and re-checked
12. Share of soils without severe limits for a conventional septic drain field (USDA SSURGO): Bolthole Index county data
13. Jefferson County Code Enforcement Division (Permit FAQs) (jeffcomo.gov)
14. Driveway Permit, quoted and re-checked
15. Permits | Missouri Department of Transportation (Missouri statewide rule), quoted and re-checked
16. Jefferson County Planning Division (jeffcomo.gov)
17. Inspections, quoted and re-checked
18. Jefferson County Building Code Fee Schedule (Section 500.250) (jeffcomo.gov)
19. Jefferson County Code Enforcement Division (Building Permit Application) (jeffcomo.gov)
20. (2026 county census)
21. Development Review, quoted and re-checked
22. Jefferson County Planning Division (Unified Development Order) (jeffcomo.gov)
23. On-Site Sewage Treatment System Permit Application, quoted and re-checked
24. Residential Building Permit Application Checklist, quoted and re-checked
25. Onsite Wastewater Treatment System Inspections Versus Evaluations (Missouri statewide rule), quoted and re-checked
26. Exhibit A — Jefferson County 2025 Flood Damage Prevention Ordinance, quoted and re-checked
27. Wooded share of land: Bolthole Index county data
28. Share of land at 15% slope or less: Bolthole Index county data
29. Effective property tax rate: Bolthole Index county data
30. Median property tax bill: Bolthole Index county data
31. Jefferson County Code Enforcement Division (On-Site Sewage Treatment System Permits) (jeffcomo.gov)

Written September 29, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.