Bolthole Index

St. Louis County, Missouri

Building permits, zoning and septic rules in St. Louis County, Missouri

43Index Score / 100
#114 of 115 in Missouri

St. Louis County, Missouri requires a building permit before you build a home in unincorporated areas, under the county's Chapter 1115 building code1. The county also administers its Zoning Ordinance for unincorporated land2. Most onsite wastewater installations or repairs require a permit, and only 5.4% of county soils avoid severe limits for a conventional drain field34.

At a glance

Building permit
Required in unincorporated St. Louis County; the Dept. of Transportation and Public Works issues it under Chapter 11151
Zoning
Countywide Zoning Ordinance (Title X, Chapter 1003) for unincorporated land, adopted under the county's first-class charter authority25
Septic
A permit is required for most installations and repairs; confirm the correct county authority and any exemption before work63
Private well
Well and pump permits generally apply, but Missouri allows a landowner to install their own well or pump without a permit7
Owner-builder
Not confirmed in official materials reviewed; ask the county directly before assuming you can self-permit8
Agricultural exemption
Farm buildings and structures are exempt from county fire-protection/fire-prevention ordinances statewide9
Driveway access
A permit is required only if the driveway touches a MoDOT state highway right-of-way10

Who to call

Building permits

St. Louis County Department of Transportation and Public Works — Codes and Ordinances

Residential building permits, the county building code (Chapter 1115) and the county Zoning Ordinance (Title X, Chapter 1003) for unincorporated St. Louis County

314-615-5184

41 South Central Avenue, 6th Floor, Clayton, MO 63105

Septic permits

St. Louis County Department of Public Health

Septic (onsite wastewater) permitting and licensed-installer requirements for St. Louis County

(314) 615-0600

[email protected]

6121 N Hanley Rd, Berkeley, MO 63134

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 St. Louis County, Missouri?

Yes, in unincorporated St. Louis County. The county is a charter county that has adopted its own building code, codified as Chapter 1115, and the Department of Transportation and Public Works requires a permit for residential construction under it1. Missouri law leaves fire and building codes to be adopted at the local level, which is exactly what St. Louis County has done rather than relying on a state-mandated code11. Whether the county offers an owner-builder path — letting you pull your own permit without a licensed contractor — was not confirmed in the official pages reviewed for this guide; ask the Codes and Ordinances office directly before you plan around it8.

Who is the St. Louis County building department, and how do you reach them?

The St. Louis County Department of Transportation and Public Works handles residential building permits and codes and ordinances questions; its Codes and Ordinances office is at 41 South Central Avenue, 6th Floor, Clayton, MO 63105, phone 314-615-518412. This same department also administers the county's Zoning Ordinance, so it's the right first call for both a building permit and a zoning question on unincorporated land2. If your parcel sits inside one of the county's many incorporated cities, its own city hall — not the county — issues permits and sets zoning there; the county's authority runs only to unincorporated territory5.

Does St. Louis County have zoning?

Yes, for unincorporated land. St. Louis County administers a Zoning Ordinance, Title X, Chapter 1003, governing land use outside its many incorporated cities2. The county can do this because it's a first-class charter county, which Missouri law empowers to zone under RSMo § 64.090 without the voter referendum that non-charter counties need5. St. Louis County has dozens of incorporated municipalities carved out of it, each free to set its own zoning; before you buy, confirm with the county whether your specific parcel is unincorporated or falls inside one of those cities, since that determines who you deal with for zoning and, often, building permits too5.

How do septic permits work in St. Louis County?

A construction permit is required before installing or repairing most onsite wastewater systems in St. Louis County, although some single-family lots may qualify for an exemption3. Missouri identifies both the St. Louis County Plumbing Department and the St. Louis County Department of Public Health as local ordinance authorities, and incorporated areas may be handled differently, so confirm the correct authority before work begins6. State rules generally require a permit on residential property smaller than three acres, but the larger-lot exemption does not apply in every county13. Only 5.4% of county soils avoid severe limitations for a conventional drain field, so get the site evaluated before assuming a standard system will work4.

Can you live in an RV or tiny home on your land in St. Louis County?

This isn't answered by the official county pages reviewed for this guide. The county's zoning ordinance (Title X, Chapter 1003) governs land use countywide in unincorporated areas, but the specific rules on RV occupancy or tiny homes as a standalone residence weren't found in the pages checked2. Don't assume either is allowed on a bare rural lot: call the Department of Transportation and Public Works' Codes and Ordinances office before you buy with the intent to live in an RV or tiny home while you build12.

Building a home in St. Louis County: the steps, in order

  1. Confirm whether the parcel is in unincorporated St. Louis County because that determines which zoning authority applies5.
  2. Check the county zoning district before fixing the house location or design2.
  3. If the property needs onsite wastewater, identify the correct county authority and obtain a permit or written confirmation of an exemption before work63.
  4. For a private water supply, arrange the required well and pump permits unless the landowner-installation exception applies7.
  5. Apply to the Department of Transportation and Public Works for the residential building permit required under Chapter 11151.
  6. Obtain a MoDOT access permit if the driveway enters state highway right-of-way10.

What to check before you buy land in St. Louis County

Septic and soils: only 5.4% of county soils avoid severe limits for a conventional drain field, so get a site evaluation before counting on a standard system4. Water: Missouri generally requires permits to construct or repair a private well and to install or replace its pump, although a landowner may install their own without a permit7. Flood risk: one county planning record required a floodplain development permit before site-plan approval for work in a mapped Special Flood Hazard Area, but that record was parcel-specific; ask the building office what applies to your tract14. Access: MoDOT requires a permit for driveway work in state right-of-way10. The effective property tax rate is about 1.2%, with a median annual bill near $3,1931516. The county has about 1,944 people per square mile, and the nearest city of 100,000 or more is about 15 miles from the county center1718.

Watch-outs

  • St. Louis County's zoning and building authority runs only to unincorporated land; if your parcel is inside one of the county's incorporated cities, that city's own hall sets zoning and, often, issues building permits instead5.
  • Whether St. Louis County lets an owner pull their own building permit without a licensed contractor was not confirmed in the official pages reviewed for this guide; ask the Codes and Ordinances office directly rather than assuming an owner-builder path exists8.
  • Missouri's septic exemption for some single-family lots does not settle the answer in St. Louis County; identify the correct county authority and confirm an exemption before starting work63.
  • A St. Louis County planning record required a floodplain development permit for work in a mapped Special Flood Hazard Area, but the evidence is parcel-specific; ask the building office for the rule on your tract14.

Sources

  1. St. Louis County - Residential Building (2026 county census)
  2. St. Louis County - Codes and Ordinances (2026 county census)
  3. OWTS Construction Permit Process, quoted and re-checked
  4. Share of soils without severe limits for a conventional septic drain field (USDA SSURGO): Bolthole Index county data
  5. RSMo § 64.090 — Planning and zoning powers of county commission (Missouri statewide rule), quoted and re-checked
  6. OWTS Construction Permit Process — St. Louis County authorities, quoted and re-checked
  7. Water Wells - PUB2945, quoted and re-checked
  8. (2026 county census)
  9. RSMo Section 64.003 — Farm buildings and farm structures (Missouri statewide rule), quoted and re-checked
  10. Permits | Missouri Department of Transportation (Missouri statewide rule), quoted and re-checked
  11. RSMo Section 64.170 (Missouri statewide rule), quoted and re-checked
  12. St. Louis County Department of Transportation and Public Works — Codes and Ordinances (stlouiscountymo.gov)
  13. OWTS Construction Permit Process (Missouri statewide rule), quoted and re-checked
  14. P.C. 25-23 Weidman Properties 3 LLC — Department of Transportation and Public Works Public Hearing, quoted and re-checked
  15. Effective property tax rate: Bolthole Index county data
  16. Median property tax bill: Bolthole Index county data
  17. Population density: Bolthole Index county data
  18. Distance to the nearest metro area: 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

St. Louis County in Missouri

43
County map
St. Louis County highlighted among the Missouri counties · colored by Index score

How St. Louis County scores

Seclusion17100% ev.
Self-Sufficiency6198% ev.
Admin Boringness4690% ev.
Durability51100% ev.
Property Autonomy47100% ev.
Carry Cost60100% 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 →

$293kTypical home
1.2%Property tax
$10,928Land / acre
42.3"Annual rain
3.4% of yrsSevere drought
13.8 / yr (+12)Mid-century 100°F days
17 daysMid-century dry spell
1.98" (+8.6%)Mid-century 1-day rain
1.83×Wildfire change factor
100%Forward climate coverage
$2,076Home insurance / yr
0.8% / yrInsurance growth
1.17%Nonrenewal rate
county median (2+ published ZIPs)Insurance basis
823,481People within 30 min
3,865,264People within 2 hr
994,727Radius comparison (15 mi)
1,943.5People / sq mi
0.5%Federal land
84.2%Land at 15% slope or less
5.4%Septic soil without severe limits
9,793 acWorkable land screen
60.4 tonsBiomass / forest ac
56.2°FAvg temp

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Answers from the rulebook for St. Louis County

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

St. Louis County rules

  • Who permits septicCounty (with conditions)

    Onsite wastewater permitting in St. Louis County, subject to the type of system and incorporated-area jurisdiction.

    • The Missouri DHSS page identifies both St Louis County Plumbing Dept. and St Louis County Department of Public Health as ordinance authorities.
    • The county's ordinance may impose requirements beyond state minimum standards.
    • Incorporated areas may be handled differently.
    • DNR regulates systems outside DHSS scope, including non-single-family lagoons, surface-water discharges, flows over 3,000 gallons per day, and industrial wastewater.

    domestic wastewater flow threshold: <= 3000 gallons per day (DNR regulates systems over this threshold)

    “Agency: St Louis County Plumbing Dept. Authority Type: Ordinance [...] County: St. Louis (County)”
  • Septic permitRequired

    Installation or repair of most onsite wastewater treatment systems in St. Louis County.

    • Some single-family residential lots may be exempt.
    • The appropriate county permitting authority must be determined before work begins.
    • Work should not begin until a permit is issued or an exemption is confirmed.
    • The county ordinance may impose requirements beyond state minimum standards.
    • Application fees associated with onsite sewage disposal construction, modifications, and repairs are temporarily suspended effective August 28, 2026, according to the state page.

    temporary fee suspension effective date: 2026-08-28 (The source states fees are temporarily suspended pending new standards)

    “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.”
  • Building in a floodplainRequired

    Work proposed within any Special Flood Hazard Area on the tract identified as P.C. 25-23, Weidman Properties 3 LLC, in St. Louis County.

    • A portion of the tract is located in Zone AE of FEMA’s Flood Insurance Rate Map.
    • The Floodplain Development Permit is required prior to approval of the Site Development Plan when work is proposed within any Special Flood Hazard Area.
    • A flood plain study may be required, as directed by the Department of Transportation and Public Works.
    • A land disturbance permit is required prior to any grading on the site, and no change in watersheds is permitted.
    • The source is a parcel-specific county planning document and does not independently establish a countywide rule for every parcel.
    “A portion of this tract is located in Zone “AE” of FEMA’s Flood Insurance Rate Map. A Floodplain Development Permit shall be required prior to the approval of the Site Development Plan when work is proposed within any Special Flood Hazard Area.”
  • Building permitRequired

    St. Louis County is a charter county with an adopted building code (Chapter 1115); the Department of Transportation and Public Works requires building permits for residential construction in unincorporated areas.

    St. Louis County - Residential Building ↗Scouted from the county site, not yet independently re-checked

  • County-wide zoningPresent

    The county administers a Zoning Ordinance (Title X, Chapter 1003) governing land use in unincorporated St. Louis County.

    St. Louis County - Codes and Ordinances ↗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”
  • 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 permitRequired

    Construction or repair of water wells in Missouri, including St. Louis County.

    • A non-restricted water-well installation permit is required to construct or repair a water well.
    • A non-restricted pump permit is required to install or replace a pump and for associated plumbing/electrical lines to the point of entry.
    • Landowners may install their own well or pump without a permit under the cited law and rules.
    • Public wells require written approval before construction, subject to statutory exemptions.
    “A non-restricted water well installation permit is required to construct or repair a water well in Missouri.”
  • 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”
  • 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 building requirements.
  • Inspections — Building inspections in unincorporated St. Louis County.
  • Certificate of occupancy — Certificates or occupancy permits for residential premises in unincorporated St. Louis County.
  • Local zoning — Local zoning in unincorporated areas and incorporated municipalities of St. Louis County.
  • Zoning districts — Published zoning districts for unincorporated St. Louis 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 St. Louis County, Missouri

Is St. Louis County a good place to live off-grid or homestead?

St. Louis County scores 43/100 on the Bolthole Index, a marginal county profile. Its strengths: workable self-sufficiency basics (42.3″/yr rainfall) and higher long-term carry cost. Watch-outs: about 823,481 people within a 30-minute drive.

Do you need a building permit in St. Louis County, Missouri?

St. Louis County generally requires a residential building permit, and it enforces county zoning. Onsite septic is permitted by St. Louis County Department of Public Health. 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 St. Louis County, Missouri?

Land in St. Louis County runs about $10,928 per acre, based on the latest county data.

What is the water situation in St. Louis County?

St. Louis County gets about 42.3" of rain a year, with severe drought in roughly 3.4% of years.

How remote is St. Louis County?

A representative private-land location has about 823,481 people within a 30-minute drive and 3,865,264 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 St. Louis County means bringing your own water and power. The kit we’d start with:

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How St. Louis compares in Missouri

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