In unincorporated Warren County, every structure, whatever its size or use, needs a structure permit from Warren County Planning and Zoning, 101 Mockingbird Lane, Suite 201, Warrenton (636-456-3044). A house is $150 under the fee schedule of February 3, 2026, a septic permit from the county Sanitarian ($200) must come first, and fees double if work starts without the permit. This is a zoning permit, and unincorporated Warren County does not require a certificate of occupancy; the Warrenton and Wright City fire protection districts require their own building permits.
Warren County building department: who handles permitting
Planning and Zoning administers the county Zoning Code (the 1985 Zone Order, now the 2021 Zoning Code with amendments from 2023 to 2026) and the floodplain ordinance. Its office is open Monday to Friday, 8 a.m. to 4:30 p.m., and the county asks applicants to call ahead to be sure staff are in. The Sanitarian, who issues septic permits, works from the same suite (636-456-7169). The county sends a monthly list of its permits to the local fire districts; the Warrenton Fire Protection District (636-456-8935) and the Wright City Fire Protection District (636-745-2262) each require a building permit of their own.
The cities and villages handle permits inside their limits. Populations are Census Bureau Vintage 2025 estimates for the part of each place in Warren County.
Short on time to read all of this?
Get a free quote →| Place | Who permits building work |
|---|---|
| Warrenton (9,667) | City Building Department, City Hall, 200 West Booneslick Road; 636-456-3535. Permit fee 0.40% and plan review 0.15% of construction cost, under the 2015 International Building and Residential Codes and 2014 NEC |
| Wright City (5,854) | City Building Official; the City Code adopts the 2015 International Building and Residential Codes and 2014 NEC, and requires an occupancy permit on each change of owner or tenant |
| Marthasville (1,302) | City Clerk’s Office (636-433-5554), which issues the City’s permits; the posted City Code has no building code, and the City lists floodplain development, water and sewer connection, and ditch or trench permits |
| Truesdale (1,054) | City Hall (636-456-3166); the City Building Inspector inspects all new homes. The City Code and the City’s permits page adopt the 2021 International Building and Residential Codes |
| Innsbrook (653) | Village of Innsbrook, which issues a zoning certificate as its building permit; Village Hall 636-745-8844 |
| Foristell (453 here; most of the city is in St. Charles County) | City Building & Code Enforcement; 636-463-2123. The City Code adopts the 2021 International Building and Residential Codes |
| Pendleton (30), Three Creeks (6) | The published sources do not say; ask the village |
What needs a county permit
Structure permit
- Houses, modular and manufactured homes
- Mobile homes, RVs and campers placed on a lot
- Additions and in-ground pools
- Improvements and accessory buildings of every size
- Privacy fences
- Commercial, multi-family and duplex buildings
- Shipping containers, signs and towers
Other county approvals
- Septic permit from the Sanitarian, before the structure permit
- Floodplain development permit and elevation certificate
- Conditional use permits, rezonings and variances
- Subdivision plats
- Electric stickers for utility service
Some non-residential uses need a conditional use permit before a structure permit can be issued. A new entrance onto a state road goes to MoDOT (573-248-2490), and onto a county road to the County Road & Bridge Department (636-456-3512).
Not sure this scope needs a permit?
Get a free quote →Warren County permit fees
| Permit | Fee |
|---|---|
| Single-family house or manufactured dwelling | $150 |
| Mobile home, RV or camper | $100 |
| Home addition or in-ground pool | $70 |
| Privacy fence | $60 |
| Improvement 120 sq ft or less | No charge |
| Improvement 121–250 / 251–1,000 sq ft | $60 / $70 |
| Improvement 1,001–2,000 / over 2,000 sq ft | $95 / $120 |
| Commercial building or addition, multi-family or duplex | $100 plus 5¢ per sq ft |
| Shipping container | $100 |
| Septic permit | $200 |
| Holding tank annual inspection | $50 |
| Conditional use, rezoning or variance | $2,000 each, plus certified mailing costs |
| Preliminary plat / final plat | $500 minimum or $30 per lot / $100 |
| Electric sticker / zoning certification letter | $10 / $25 |
Fees double if the right permit is not obtained before the project starts. For example, a 10,000 sq ft commercial building is $100 plus $500, or $600. Checks are payable to the Warren County Treasurer.
What to bring for a house permit
- A copy of the building plans, or for a manufactured home its layout with make, model and year and the title or bill of sale
- An address assigned by the 911 Business Office (636-456-7088)
- The recorded warranty deed if the property was bought within the last six months
- Photo ID of the owner, or of a representative with the owner’s notarized affidavit; trusts and LLCs must show who can sign
- The completed application and fee
- For a septic system, a soil evaluation by a state- and county-approved soil scientist and the septic permit
Rather talk it over?
Call 1-855-478-4290 →Plans are returned after review unless the building is in the floodplain. If a new home replaces an existing one, the old home must be removed within 60 days.
How to get a Warren County structure permit
Make sure the parcel is outside the cities and that the use is allowed in its zoning district.
Order the soil evaluation, submit the design and get the Sanitarian’s permit; septic and structure permits can be issued on the same visit if both offices are ready.
Every parcel is checked; in the floodplain, the elevation certificate and floodplain permit come before the zoning permit.
Bring the documents and fee to 101 Mockingbird Lane, Suite 201, and post the permit at the site; it expires after one year.
In the Warrenton or Wright City fire district, apply for the district’s building permit too.
A temporary electric sticker comes with the permit; the permanent one is released after the septic system passes its final inspection.
Rather not deal with the Warren County building department?
Get a free quote →Floodplain, septic and data center rules
Floodplain: the county takes part in the National Flood Insurance Program, with flood maps dated November 4, 2009. Under Floodplain Management Ordinance 2009-01, new and substantially improved buildings need the lowest floor, basement included, 1 ft above the base flood elevation. Before a floodplain development permit or zoning permit is issued, submit an original elevation certificate sealed by a surveyor, engineer or architect and based on finished construction, with a site plan and the building plans; faxed or emailed copies are not accepted.
Septic: the county’s own regulations govern the design, construction and modification of onsite sewage systems, and the Sanitarian issues the $200 permit. Call ahead (636-456-7169) to make sure the design sheets have arrived and staff are in; the office posts the 2026 list of installers authorized and registered by the state and the county.
Data centers: a 2026 amendment to the Zoning Code (Commission Order 08-2026) allows “information technology and data processing facilities” only as a conditional use in the I-1 district, at least 200 ft from adjacent lot lines and 300 ft from any residential structure, no taller than 35 ft or two floors, and cooled only by closed-loop or air-cooled systems, with no evaporative cooling of any kind.
Missouri building code
Missouri has no mandatory statewide building code for private construction: a county, fire protection district or municipality may adopt one (usually by reference under RSMo 67.280), and in parts of the state none has. Building codes in Missouri
Warren County permit FAQs
Does Warren County require a building permit?
It requires a structure (zoning) permit from Planning and Zoning for every structure in the unincorporated county, and it does not require a certificate of occupancy. The Warrenton and Wright City fire districts require building permits of their own.
How much is a structure permit for a new house?
$150 for a single-family house or manufactured dwelling, plus $200 for the septic permit if the house is on a septic system.
Do I need a permit for a small shed?
Yes, every structure needs one, but an improvement of 120 sq ft or less is free; 121–250 sq ft is $60.
Want this handled start to finish?
Get a free quote →What happens if I build without a permit?
The permit fee doubles, and violations can be prosecuted.
Who issues permits in Warrenton or Wright City?
The cities themselves: Warrenton’s Building Department at City Hall (636-456-3535) and Wright City’s Building Official.
How high must a home be built in the floodplain?
Its lowest floor, including any basement, must be 1 ft above the base flood elevation, shown on a sealed elevation certificate.
Warren County permit search and official resources
- Warren County Planning and Zoning
- Warren County structure permit packet (2026)
- Warren County Planning and Zoning fee schedule (February 3, 2026)
- Warren County Zoning Code with 2023–2026 amendments
- Building a structure in the Warren County floodplain
- Warren County Floodplain Management Ordinance
- Warren County Sanitarian (septic permits)
- FEMA Community Status Book: Missouri
- City of Warrenton building permits and fees
- City of Truesdale building codes (Chapter 500)
- Village of Innsbrook forms and fees
Inspections are where schedules slip.
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Read guide →This guide is provided by Alliance Permitting for general information about Warren County permitting. Requirements, fees, and procedures change; confirm details with the permitting authority before relying on them.