Bolthole Index

Franklin County, Missouri

Building permits, zoning and septic rules in Franklin County, Missouri

66Index Score / 100
#80 of 115 in Missouri

Unincorporated Franklin County, Missouri requires a building permit for new construction, and the county's Building Department inspects the work under locally adopted codes1. The county also zones unincorporated land through its Planning & Zoning Department, which reviews land divisions, rezoning, conditional use permits and variances2. Septic systems go through the county's own On-Site Sewage Disposal Systems Ordinance rather than a state or health-department office3.

At a glance

Building permit
Required for new construction in unincorporated Franklin County1
Zoning
Yes; the county Planning & Zoning Department zones unincorporated areas2
Septic permit
County-issued under Franklin County's own On-Site Sewage Disposal Systems Ordinance, amended effective October 1, 202534
Driveway/road access
County entrance permit needed for a driveway onto a county-maintained road; a state permit is needed onto a state highway56
Owner-builder exemption
Not stated on the county's site; confirm with the Building Department7
Building codes
2021 International codes plus the 2020 National Electric Code, in effect since April 23, 20244
Water wells
Permits apply to well and pump work, but a landowner may install their own well or pump without a permit8

Who to call

Building permits

Franklin County Building Department

Building permits, inspections, mobile-home permits and on-site sewage (septic) permits for unincorporated Franklin County

636-583-6384

[email protected]

400 East Locust, Union, MO 63084

Zoning

Franklin County Planning & Zoning Department

Zoning, land divisions, rezoning, conditional use permits, variances and floodplain administration for unincorporated Franklin County

636-583-6369

[email protected]

400 East Locust, Union, MO 63084

Roads & driveways

Franklin County Highway Department

Entrance (driveway) permits and right-of-way permits onto county-maintained roads in Franklin County

636-583-6361

400 East Locust, Union, MO 63084

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 Franklin County, Missouri?

Yes. Unincorporated Franklin County, Missouri requires a building permit for new construction, and the county Building Department inspects the work to meet locally adopted codes1. Missouri's building-code authority is set at the local level rather than by one statewide code: state law lets a qualifying county adopt a current nationally recognized building code and enforce it through permits and inspections9. Franklin County has adopted the 2021 editions of the International Building, Residential, Mechanical, Plumbing and Fire Codes, the 2020 National Electric Code, and the ISPSC swimming pool and spa code, with amendments in effect since April 23, 20244. Farm buildings and farm structures are exempt from a county's fire-protection or fire-prevention ordinance under a 2025 state law, though that exemption does not cover other zoning, building-code, floodplain or septic requirements10.

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

The Franklin County Building Department issues permits and inspects new construction of structures within unincorporated Franklin County to meet minimum public-safety, health and welfare standards under the adopted code4. Reach the department at 636-583-6384, by email at [email protected], or in person at 400 East Locust in Union, Missouri4. Its applications cover single-family homes, mobile homes, additions, pools, solar installations and storage buildings, and the same office's Sewer Permit Application form covers on-site sewage systems4. Before applying, check the current fee schedule and the county's permit escrow requirements, both linked from the Building Department's page4.

Does Franklin County have zoning?

Yes. Franklin County zones unincorporated land through its Planning & Zoning Department, which regulates land divisions, lot-line adjustments, zoning districts, address assignments, road naming and floodplain administration211. The department also handles rezoning requests, conditional use permits, zoning enforcement and requests for variances under the county's Unified Land-Use Regulations11. Missouri generally requires a countywide voter-approved zoning question before a non-charter county can zone, which is why some unincorporated Missouri counties have no zoning at all12. Franklin County's own site does not publish a countywide minimum lot size, RV-occupancy rule or setback figure, so a property's specific zoning district controls what is allowed there; a Zoning Permit/Verification from the Planning & Zoning Department confirms the zoning district of a specific parcel and whether a specific use is permitted before you buy11.

How do septic permits work in Franklin County?

Franklin County issues septic permits itself rather than routing them through a state agency: the Building Department's Sewer Permit Application covers on-site sewage systems, and the county has its own On-Site Sewage Disposal Systems Ordinance, adopted and amended September 23, 2025 and effective October 1, 202534. Statewide, Missouri splits septic authority between the Department of Natural Resources for larger discharges and lagoons and the Department of Health and Senior Services or a local agency, typically a county health department, for single-family systems at or below 3,000 gallons per day; Franklin County acts as that local agency13. Only about 2.2% of Franklin County's soils rate free of severe limits for a conventional septic drain field under USDA's soil survey, so plan on a site evaluation and budget for an engineered or mound system on much of the county's land14. A state construction permit is generally required before installing or repairing most onsite systems, and the small-lot exemption does not apply in every county, so confirm directly with Franklin County's Building Department rather than assuming an exemption applies15. Missouri's local health agencies generally no longer inspect existing systems for real-estate transfers, so a buyer relying on an existing septic system should hire a private licensed inspector16.

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

Franklin County's Building Department permits manufactured housing through its own Mobile Home Permit Application and Mobile Home Application Checklist, which shows the county treats a manufactured home as a permitted structure rather than an unregulated use4. Whether a recreational vehicle can serve as a residence, and for how long, depends on the zoning district that applies to a specific parcel; Franklin County's own pages do not publish a countywide RV-occupancy rule, so this is not yet confirmed11. Get a Zoning Permit/Verification from the Planning & Zoning Department before you buy or move a home onto a parcel: it confirms the zoning district of that property and whether a specific use, including RV or tiny-home occupancy, is permitted there11. Statewide rules about licensed campgrounds and RV parks are a different question from whether you can live in your own RV on your own rural land, so do not treat one as an answer to the other.

Building a home in Franklin County: the steps, in order

  1. Get a zoning verification. Call or visit the Planning & Zoning Department to confirm your parcel's zoning district and that a single-family home, or an RV or tiny home if that is the plan, is a permitted use there11.
  2. Check soils and plan septic early. With only 2.2% of county soils rated free of severe limits for a conventional drain field, get a site evaluation before you design the house, since many lots need an engineered or mound system14.
  3. Apply for a septic permit. Franklin County's Building Department issues the on-site sewage permit under the county's On-Site Sewage Disposal Systems Ordinance, effective October 1, 202543.
  4. Apply for the building permit. Submit the Building Permit Application and required checklist to the Building Department, which reviews plans against the adopted 2021 International codes before construction starts41.
  5. Get a driveway or entrance permit. A driveway onto a county-maintained road needs an entrance permit from the Highway Department; a driveway onto a state highway needs a separate MoDOT permit56.
  6. Schedule inspections. The Building Department inspects the work as it progresses under the adopted code4.

What to check before you buy land in Franklin County

Confirm the parcel's zoning district with Franklin County's Planning & Zoning Department before you buy, since setbacks, minimum lot size and allowed uses vary by district and are not published county-wide11. Get a soil evaluation for septic suitability: Franklin County rates only 2.2% of its soils free of severe limits for a conventional drain field, so budget for an engineered system unless a site test says otherwise14. If the land needs a private well, Missouri requires permits for well construction or repair and for pump installation or replacement, but a landowner may install their own well or pump without a permit; contractors and people directing the work need the applicable permit8. Ask whether the parcel sits in a mapped flood hazard area, since the Planning & Zoning Department administers floodplain development under the county's Flood Damage Prevention Ordinance11. If the parcel fronts a state highway, budget for a MoDOT driveway permit in addition to any county permits6. Franklin County's median property tax bill runs about $1,774 a year at an effective rate near 0.8%, and the typical home value in the county is about $273,172, so use those figures to estimate carrying costs on a comparable property171819.

Watch-outs

  • Franklin County adopted and amended its On-Site Sewage Disposal Systems Ordinance on September 23, 2025, effective October 1, 2025, so confirm septic requirements against the current ordinance rather than an older summary43.
  • Franklin County's own pages do not state a countywide RV-occupancy or tiny-home rule, so get a zoning verification for your specific parcel before assuming it is allowed11.
  • Franklin County has not published an owner-builder exemption from its building-permit process; confirm with the Building Department before assuming you can pull your own permit7.

Sources

  1. Franklin County Building Department (2026 county census)
  2. Franklin County Planning and Zoning Department (2026 county census)
  3. Franklin County - Permits (2026 county census)
  4. Franklin County Building Department (franklinmo.gov)
  5. Franklin County Highway Department (franklinmo.gov)
  6. Permits | Missouri Department of Transportation (Missouri statewide rule), quoted and re-checked
  7. (2026 county census)
  8. Water Wells - PUB2945, quoted and re-checked
  9. RSMo Section 64.170 (Missouri statewide rule), quoted and re-checked
  10. RSMo Section 64.003 — Farm buildings and farm structures (Missouri statewide rule), quoted and re-checked
  11. Franklin County Planning & Zoning Department (franklinmo.gov)
  12. RSMo § 64.090 — Planning and zoning powers of county commission (Missouri statewide rule), quoted and re-checked
  13. On-site Septic Systems and Subdivisions (Missouri statewide rule), quoted and re-checked
  14. Share of soils without severe limits for a conventional septic drain field (USDA SSURGO): Bolthole Index county data
  15. OWTS Construction Permit Process (Missouri statewide rule), quoted and re-checked
  16. Onsite Wastewater Treatment System Inspections Versus Evaluations (Missouri statewide rule), quoted and re-checked
  17. Median property tax bill: Bolthole Index county data
  18. Effective property tax rate: Bolthole Index county data
  19. Typical home value (Zillow): Bolthole Index county data

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.

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County locator

Franklin County in Missouri

66
County map
Franklin County highlighted among the Missouri counties · colored by Index score

How Franklin County scores

Seclusion52100% ev.
Self-Sufficiency69100% ev.
Admin Boringness4690% ev.
Durability56100% ev.
Property Autonomy47100% ev.
Carry Cost74100% ev.

Evidence strength: 98%. This reports direct-source completeness and fallback use; it is separate from the score and is not a confidence interval. How it works →

$273kTypical home
0.8%Property tax
$5,647Land / acre
43.1"Annual rain
4.4% of yrsSevere drought
15.8 / yr (+12.9)Mid-century 100°F days
15.9 daysMid-century dry spell
1.98" (+8.4%)Mid-century 1-day rain
1.84×Wildfire change factor
100%Forward climate coverage
$2,121Home insurance / yr
2.2% / yrInsurance growth
1.23%Nonrenewal rate
county median (2+ published ZIPs)Insurance basis
27,459People within 30 min
3,402,236People within 2 hr
59,530Radius comparison (15 mi)
115.3People / sq mi
0.1%Federal land
72.9%Land at 15% slope or less
2.2%Septic soil without severe limits
12,920 acWorkable land screen
60.3%Wooded land
49.5 tonsBiomass / forest ac
55.3°FAvg temp

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Answers from the rulebook for Franklin County

What the ordinances and state agencies actually say — one answer per question, each quoted from the official source and independently re-checked.

Franklin County rules

  • Building permitRequired

    The county Building Department issues permits and inspects new construction of structures within unincorporated Franklin County per adopted code, to safeguard public safety, health and welfare.

    Franklin County Building Department ↗Scouted from the county site, not yet independently re-checked

  • County-wide zoningPresent

    The county Planning and Zoning Department regulates zoning districts, land divisions, rezoning, conditional use permits and variances in unincorporated Franklin County.

    Franklin County Planning and Zoning Department ↗Scouted from the county site, not yet independently re-checked

Missouri rules that apply here

  • Building code adoptedPartial

    Missouri statewide legal framework for building-code adoption by counties and other communities; the statutes authorize local adoption rather than establishing one uniformly adopted statewide building code.

    • County authority under RSMo 64.170 applies to counties of the first and second classification.
    • A county that had not adopted a building code before August 28, 2001 must obtain voter approval before adopting under RSMo 64.170 to 64.200.
    • The adoption vote is limited to voters in the affected area; a code affecting a county is not voted on by citizens of incorporated territory.
    • A county adopting under RSMo 64.180 must use a current nationally recognized building code edition from calendar year 1999 or later, as amended.
    • A county building ordinance may not conflict with liquefied petroleum gas installation requirements governed by RSMo 323.020.
    • A community may incorporate a code by reference only if it otherwise has legal power to adopt the ordinance.
    • A code incorporated by reference must be filed with the community clerk and available for public inspection for 90 days before adoption.
    • An ordinance adopting a code by reference must state the penalty separately rather than incorporate the penalty by reference.
    • RSMo 67.280 defines community to include any county, fire protection district, or municipality, and municipality to include an incorporated city, town, or village.
    “Because fire and building codes are adopted at the local level in Missouri”
  • Who permits septicMixed

    Missouri wastewater treatment systems, including domestic onsite systems, larger-flow systems, direct discharges, lagoons, subdivisions, and industrial wastewater.

    • DNR regulates direct point-discharge or surface-land-application systems, non-individual lagoons, facilities exceeding 3,000 gallons per day, and industrial process waste.
    • DHSS or a local agency, typically the county health department, regulates single-family subsurface onsite systems, individual single-family lagoons, and qualifying systems at or below 3,000 gallons per day.
    • Local agencies may administer qualifying systems under local authority or ordinance.

    domestic wastewater flow threshold: <= 3000 gallons per day (DNR regulates facilities with domestic wastewater flow greater than 3,000 gallons per day)

    “In Missouri, different state and local agencies are responsible for regulating wastewater treatment systems.”
  • Septic permitRequired

    Installing or repairing most onsite wastewater treatment systems in Missouri, including residential systems subject to state permitting.

    • A construction permit is required before installing or repairing most OWTS.
    • Some single-family residential lots may be exempt.
    • For residential property less than three acres, a permit is required; the exemption does not apply in some counties, so the county authority must be checked.
    • Work should not begin until a permit is issued or an exemption is confirmed.
    • Effective August 28, 2026, application fees for onsite sewage disposal system construction, modifications, and repairs are temporarily suspended.

    residential lot threshold: < 3 acres (The exemption does not apply in some counties.) · temporary permit-fee suspension effective date: 2026-08-28 (Applies to application fees associated with onsite sewage disposal system construction, modifications, and repairs.)

    “A construction permit is required before installing or repairing most onsite wastewater treatment systems (OWTS). Some single family residential lots may be exempt from permitting.”
  • Septic inspectionLimited

    Inspection or evaluation of existing onsite wastewater systems in connection with Missouri real-estate transfers.

    • Local public health agencies generally no longer inspect existing systems for real-estate transfers.
    • A private licensed inspector may perform an inspection or evaluation.
    • A lender, buyer, or other transaction participant may require an assessment.
    • Some local standards may be more stringent than state regulations.
    • Inspections and evaluations are distinct; an inspection includes a hydraulic test, while an evaluation does not.
    “For the most part, local public health agencies no longer inspect existing systems related to real estate transfer. The help of a licensed inspector can be obtained to check the condition of the system.”
  • Off-grid sanitationLimited

    Off-grid domestic wastewater treatment using onsite wastewater treatment systems where central sewer service is unavailable.

    • Onsite systems treat and dispose of domestic sewage on the property where generated.
    • A construction permit is generally required, including for residential property less than three acres, subject to county-specific exceptions.
    • Wastewater may not be discharged into a road ditch or onto the ground.
    • Local permitting authorities may impose additional requirements.

    residential lot threshold: < 3 acres (The exemption does not apply in some counties.)

    “Onsite wastewater treatment systems are sometimes referred to as "septic systems." These systems treat and dispose of domestic sewage on the property where it is generated.”
  • Well permitLimited

    Water-well construction and repair in Franklin County under Missouri statewide rules.

    • A non-restricted water-well installation permit is required to construct or repair a water well in Missouri.
    • A non-restricted pump-installation permit is required to install or replace a pump and for specified plumbing and electrical work.
    • A restricted water-well or pump-installation permit is required for someone who contracts these activities or directs the installation.
    • Landowners may install their own well or pump without a permit pursuant to the cited law and rules.
    “A non-restricted water well installation permit is required [...] Landowners may install their own well or pump without a permit”
  • Agricultural exemptionAvailable (with conditions)

    Erection, maintenance, repair, alteration, or extension of farm buildings or farm structures as against county fire-protection or fire-prevention ordinances.

    • The exemption applies to fire protection or fire prevention ordinances adopted by counties in Missouri.
    • The statutory text addresses farm buildings and farm structures; it does not establish a general exemption from every zoning, building-code, floodplain, septic, or other land-use requirement.
    • Effective August 28, 2025.

    effective date: 2025-08-28

    “Notwithstanding any provision of law to the contrary, no fire protection or fire prevention ordinance adopted by any county in this state shall be exercised so as to impose regulations or to require permits with respect to the erection, maintenance, repair, alteration, or extension of farm buildings or farm structures.”
  • Driveway accessRequired

    Construction or modification of driveways within MoDOT right-of-way statewide.

    • A permit is required for construction of driveways and modifications to existing driveways on MoDOT right-of-way.
    • An initial online request must be submitted for each planned listed activity.
    • Engineered plans, traffic studies, hydraulic analysis, traffic-control plans, surety deposits, or performance bonds may be required depending on the work.
    • The rule does not establish a permit requirement for driveways outside MoDOT right-of-way.
    “We require you to obtain a permit to work on MoDOT's Right of Way for: Construction of driveways”
  • Building in a floodplainLimited

    Projects including mining, dredging, building construction, and other dirt-moving activities in designated flood hazard areas within participating Missouri jurisdictions.

    • The source describes local county or city flood damage reduction ordinances rather than one uniform statewide ordinance.
    • The project must be within a participating jurisdiction.
    • The project must be within a designated flood hazard area.
    • The cited rule does not apply if either condition is absent.
    • Covered projects must not raise flood heights.
    “Some jurisdictions (for example, county, city) require any projects in certain floodplains do not raise flood heights.”
  • Permit feesPublished (with conditions)

    Missouri Department of Natural Resources air construction permits statewide.

    • Fees apply to air construction permits, not to every Missouri building or land-use permit.
    • Construction permit fees include a filing fee and an hourly processing fee.
    • The filing fee depends on the type of construction permit.
    • The listed fees are effective January 1, 2026.
    • Fees applicable until December 31, 2025 are available on the Air Construction Permit Fees white sheet.
    • A convenience fee is charged for electronic payment.

    portable source relocation filing fee: 300 USD · minor permit filing fee: 300 USD · minor permit processing fee: per 100 USD (hour) · general permit filing fee: 700 USD · new source review filing fee: 6000 USD (plus $100 per hour processing fee) · prevention of significant deterioration filing fee: 6000 USD (plus $100 per hour processing fee) · hazardous air pollutant filing fee: 6000 USD (plus $100 per hour processing fee) · temporary or pilot filing fee: 250 USD (plus $100 per hour processing fee)

    “Construction permit fees include a filing fee and an hourly processing fee. The filing fee is dependent on the type of construction permit.”
  • Permit processPublished (with conditions)

    Permit applications for work on Missouri Department of Transportation right-of-way statewide.

    • The process applies to MoDOT right-of-way work.
    • Applicants may apply online, contact the area Traffic Specialist, or submit a hard-copy application by mail.
    • Additional documentation may be required depending on the work, including site plans, performance bond, certificate of liability, traffic studies, or a meeting with MoDOT personnel.
    • After issuance, Missouri One Call, a Notice of Intent, permit and approved-plan retention, and Traffic Specialist contact requirements apply.
    • Lane closures require a request at least two working days in advance and authorization before closing lanes.
    • The Traffic Specialist must be contacted at least 48 hours before beginning work and for necessary inspections.

    lane-closure advance request: >= 2 working days (authorization from MoDOT is also required) · Traffic Specialist pre-work contact: >= 48 hours (before beginning work)

    “Contact the Traffic Specialist a minimum of 48 hours prior to beginning work and for all necessary inspections.”
  • county zoning authorityGeneral

    Missouri counties adopting zoning regulations for unincorporated territory.

    • First-class charter counties are empowered under RSMo § 64.090; that section excludes first-class counties without a charter form of government.
    • A first-class noncharter county or a county of the second, third, or fourth class may establish county zoning under RSMo §§ 64.845 to 64.880 only after the zoning question is submitted to county voters and a majority of votes cast favors county zoning.
    • The authority applies to unincorporated portions or territory and does not apply to incorporated portions under § 64.090.
    • Section 64.090 excludes specified agricultural activities and certain farm structures, underground mining, and protects existing lawful uses subject to gradual elimination of nonconforming uses.
    “If a majority of the votes cast is in favor of county zoning, the county commission shall proceed with a program of county zoning”
  • county building authorityLimited

    County regulation of construction and issuance of building permits for buildings, including residential construction, in Missouri counties, with the practical focus on county-controlled areas outside incorporated territory.

    • RSMo § 64.170 grants the authority to counties of the first and second classification only.
    • The authority is subject to subsections 2 and 3.
    • A county that had not adopted a building code before August 28, 2001, under §§ 64.170 to 64.200, lacks authority to adopt one under those sections unless voters approve it.
    • The building-code authority vote is limited to voters in the affected area; a code affecting a county may not be voted on by citizens of incorporated territory.
    • The statute authorizes building regulations, building permits, inspections, licensing rules, and permit, license, and inspection fees.
    “the county commission in all counties of the first and second classification [...] is for this purpose empowered [...] to adopt [...] regulations to control the construction”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission — ask the county directly.

  • Owner-builder exemption — Owner-builder exemptions from county construction requirements.
  • Inspections — Building inspections in unincorporated Franklin County.
  • Certificate of occupancy — Certificates of occupancy for structures in unincorporated Franklin County.
  • Local zoning — Local zoning across Franklin County, including incorporated and unincorporated areas.
  • Zoning districts — Published zoning districts and district regulations in unincorporated Franklin County.
13 more unanswered
  • Minimum dwelling size
  • Minimum lot size
  • Setbacks
  • Lot coverage
  • Building height
  • Living in an RV
  • Camping on your land
  • Tiny homes
  • Manufactured homes
  • Accessory dwellings
  • Mandatory utility hookup
  • Subdividing land
  • Short-term rentals

Each answer was extracted from an official source and independently re-checked against that source by a second reviewer. That is an evidence check, not legal advice. Rules change; confirm with the authority before you buy or build.

Living off-grid in Franklin County, Missouri

Is Franklin County a good place to live off-grid or homestead?

Franklin County scores 66/100 on the Bolthole Index, a strong county profile. Its strengths: manageable long-term carry cost and workable self-sufficiency basics: 43.1″/yr rainfall and 60.3% wooded land.

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

Franklin County generally requires a residential building permit, and it enforces county zoning. Onsite septic is permitted by Franklin County (On-Site Sewer / Building Permits Department). These answers are quoted from official sources and independently re-checked. Rules change and cities within the county differ — always confirm with the county before you buy or build.

How much does land cost in Franklin County, Missouri?

Land in Franklin County runs about $5,647 per acre, based on the latest county data.

What is the water situation in Franklin County?

Franklin County gets about 43.1" of rain a year, with severe drought in roughly 4.4% of years.

How remote is Franklin County?

A representative private-land location has about 27,459 people within a 30-minute drive and 3,402,236 within two hours. The road-network catchments count population across county lines and clusters of smaller cities; straight-line radius values remain available as a comparison.

Off-grid gear

Going off-grid in Franklin County means bringing your own water and power. The kit we’d start with:

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How Franklin compares in Missouri

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