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

Unincorporated St. Louis County, Missouri requires a residential building permit for a new home from the county Department of Transportation and Public Works1. Zoning review applies in unincorporated areas, while properties inside cities such as Eureka get zoning approval from the municipality23. Most onsite septic installations or repairs need a county permit, and we could not confirm which county office issues it for every address45.

At a glance

Building permit
Required for residential construction in unincorporated St. Louis County1
Zoning
County review in unincorporated areas; municipal zoning approval inside municipalities26
Septic
A permit is required for most installations and repairs; confirm the correct county authority and any exemption before work54
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
Construction access
A temporary entrance needs a separate right-of-way permit when no usable driveway exists10

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

administration.doh@stlouisco.com

6121 N Hanley Rd, Berkeley, MO 63134

Contact details are copied from each office’s official page and were checked against it on October 13, 2026.

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

Yes, a new home in unincorporated St. Louis County requires a residential building permit from the Department of Transportation and Public Works1. The county code requires an owner or the owner’s agent to apply to the building official and obtain the permit before constructing, enlarging, altering, moving or demolishing a building, or before installing regulated electrical, gas, mechanical or plumbing systems11. The code lists exemptions, including one-story detached storage sheds and playhouses of no more than 120 square feet, so a small shed may not need a permit while a house does11. Inside a municipality that contracts with St. Louis County for code enforcement, municipal zoning or other local approval comes first, and the county permit follows11. County materials for residential pools also show that some code requirements are checked through field inspections and that this permit type receives a preconstruction site-inspection consultation before issuance; ask the building office for the inspection schedule that applies to a house12. We could not confirm an owner-builder exemption, so ask the Codes and Ordinances office before assuming an owner may pull the permit without a licensed contractor8.

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 for unincorporated property1. Its Codes and Ordinances office is at 41 South Central Avenue, 6th Floor, Clayton, MO 63105, and the phone number is 314-615-518413. Start there to confirm the required application, drawings, inspections and fees for a house. County guidance for residential pool permits requires an electronic application, zoning approval or site plans, and construction-ready drawings, but that guidance is not a complete checklist for a new home14. Inside a municipality, obtain zoning approval from the municipal zoning officer instead15.

Does St. Louis County have zoning?

Yes. St. Louis County administers zoning review for proposed residential work in unincorporated St. Louis County2. The county's rules apply to unincorporated land only: Eureka has its own municipal zoning chapter3, and a property inside any municipality needs site plans approved by that municipality's zoning officer, with subdivision indentures possibly adding private restrictions6. Like most counties around it in Missouri, St. Louis County requires a county building permit1. Site plans in unincorporated areas must show lot lines and label setbacks and easements; the county material we reviewed does not give one setback number for every house or district16. Confirm the parcel's jurisdiction, zoning district and project-specific setbacks before placing a home, tiny house, septic area or accessory structure.

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 exemption4. 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 begins5. State rules generally require a permit on residential property smaller than three acres, but the larger-lot exemption does not apply in every county17. 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 work18. Application fees for onsite sewage disposal construction, modification and repair were temporarily suspended effective August 28, 2026, according to the state page, so ask the issuing office whether that is still in effect4.

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

We could not confirm whether an RV may be occupied long term on a private lot or whether a tiny home may serve as a standalone residence in unincorporated St. Louis County. County zoning review applies to proposed residential work on unincorporated land, while municipal zoning officers review property inside municipalities26. Before buying for either use, give the Codes and Ordinances office the parcel address and ask about the zoning district, dwelling classification, minimum size, setbacks and temporary occupancy13. Do not treat permission to park an RV as permission to live in it.

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

  1. Confirm whether the parcel is unincorporated or inside a municipality, because county and municipal zoning review follow different paths6.
  2. Obtain zoning approval and confirm the setbacks and easements that apply to the site216.
  3. If onsite wastewater is needed, identify the correct county authority and obtain a permit or written confirmation of an exemption54.
  4. Arrange the applicable private-well and pump approvals7.
  5. Ask Transportation and Public Works for the house checklist, then submit the required residential building-permit materials1.
  6. If no usable driveway entrance exists, obtain a temporary-entrance permit from the county highway department or municipality that owns the right-of-way10.
  7. Complete the inspections assigned to the permit12.

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 system18. Water: Missouri generally requires permits for regulated private-well and pump work, although a landowner-installation exception may apply7. Flood risk: residential construction within the 100-year flood elevation has an added occupancy condition, and pools in a flood-hazard area require floodplain review before permit issuance19. Land in the county's FP Flood Plain District, an overlay on the underlying zoning, needs a development plan with an engineer's report before building, filling or grading below the flood elevation20, and any encroachment into the floodway is prohibited unless an engineer certifies no increase in flood levels21. Access: a project permit does not itself authorize construction access; a temporary entrance needs separate approval from the county or municipality owning the right-of-way when no usable entrance exists10. The effective property-tax rate is about 1.2%, with a median annual bill near $3,1932223.

Watch-outs

  • St. Louis County zoning review applies in unincorporated areas, while property inside a municipality needs municipal zoning approval and may also be subject to subdivision indentures6.
  • 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 work54.
  • Residential construction and pools in mapped flood-hazard areas face added county review or occupancy conditions, so identify the flood status before fixing a building site19.
  • Septic application fees were temporarily suspended effective August 28, 2026, and the suspension may end; confirm with the St. Louis County Department of Public Health before you apply424.

Sources

  1. Chapter 1115 - Building Code (2026 county census)
  2. Single-Family Dwelling Design Checklist, quoted and re-checked
  3. Eureka: Table of Contents - City of Eureka, MO (St. Louis County), quoted and re-checked
  4. OWTS Construction Permit Process, quoted and re-checked
  5. OWTS Construction Permit Process — St. Louis County authorities, quoted and re-checked
  6. Single-Family Dwelling Design Checklist, 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. Residential Above Ground Swimming Pool Checklist and Guide for a Building Permit, quoted and re-checked
  11. Chapter 1115 - Building Code, quoted and re-checked
  12. Residential Above Ground Swimming Pool Checklist and Guide for a Building Permit, quoted and re-checked
  13. St. Louis County Department of Transportation and Public Works — Codes and Ordinances (stlouiscountymo.gov)
  14. Residential Above Ground Swimming Pool Checklist and Guide for a Building Permit, quoted and re-checked
  15. Residential Above Ground Swimming Pool Checklist and Guide for a Building Permit, quoted and re-checked
  16. Residential Above Ground Swimming Pool Checklist and Guide for a Building Permit, quoted and re-checked
  17. OWTS Construction Permit Process (Missouri statewide rule), quoted and re-checked
  18. Share of soils USDA rates "not limited" for a conventional septic drain field (SSURGO). A strict rating: the median county is about 6% and a tenth of counties are 0%, so a low figure means most lots need a site evaluation or an engineered system, not that septic is impossible. Cite it only with that caveat: Bolthole Index county data
  19. Single-Family Dwelling Design Checklist, quoted and re-checked
  20. Bill No. 82, 2022 — Section 1003.101 FP Flood Plain District Regulations, quoted and re-checked
  21. Bill No. 82, 2022 — Section 1003.101 FP Flood Plain District Regulations, quoted and re-checked
  22. Effective property tax rate: Bolthole Index county data
  23. Median property tax bill: Bolthole Index county data
  24. St. Louis County Department of Public Health (stlouiscountymo.gov)

Written October 13, 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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Compared with neighboring counties

Like 5 of its 6 neighbors, St. Louis County requires a building permit for a home.

RuleSt. Louis CountySt. Charles CountySt. Louis CityJefferson CountyFranklin CountyLincoln CountyWarren County
Building permitRequiredRequiredRequiredRequiredRequiredNot requiredRequired
County zoningYesYesYesYesYesNoYes
Septic permitsCounty Dept. of Public HealthCounty Div. of Building & Code EnforcementMO Dept. of Health & Senior ServicesCounty Code Enforcement Div.Franklin CountyCounty Health Dept.County Sanitarian

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%Soils rated "not limited" for septic (strict USDA rating)
9,793 acWorkable land screen
60.4 tonsBiomass / forest ac
56.2°FAvg temp

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Cities and towns in St. Louis County

Inside a city or town, that city usually issues building permits and sets zoning; the county’s rules above cover unincorporated land. Septic, wells and floodplain rules usually stay with the county or state everywhere.

Not yet researched: Bella Villa · Beverly Hills · Village of Champ · Clarkson Valley · Country Club Hills · Village of Country Life Acres · Edmundson · Flordell Hills · Frontenac · Village of Hillsdale · Huntleigh · Kinloch · Maplewood · Maryland Heights · Moline Acres · Village of Pasadena Park · St. John · Village of Sycamore Hills · Town and Country · University City · Valley Park · Velda Village Hills · Warson Woods · Wellston · Village of Westwood · Village of Wilbur Park

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

  • Building permitRequired

    Construction, enlargement, alteration, repair, movement, demolition, occupancy change, or regulated electrical, gas, mechanical, or plumbing work in unincorporated St. Louis County.

    • The owner or owner's authorized agent must first apply to the building official and obtain the required permit.
    • The code lists permit exemptions, including qualifying repair work, public service agency work, one-story detached accessory structures used as tool or storage sheds, playhouses and similar uses not exceeding 120 square feet, and certain fences and retaining walls.
    • In municipalities that contract with St. Louis County for code enforcement, municipal zoning or other local approval is required before issuance of a County permit.
    “Any owner or owner's authorized agent who intends to construct, enlarge, alter, repair, move, demolish, or change the occupancy of a building or structure, or install or alter a ground level paved parking lot other than those lots serving a single-family dwelling, or establish a new or relocated lot line that affects an existing structure, or to erect, install, enlarge, alter, repair, remove, convert or replace any electrical, gas, mechanical or plumbing system, the installation of which is regulated by this code, or to cause any such work to be performed, shall first make application to the building official and obtain the required permit.”
  • Building code adoptedAdopted

    County construction codes identified in the St. Louis County residential pool permit guide.

    • The guide identifies the codes as amended and adopted by ordinance.
    • The guide lists the 2015 ISPSC, 2015 IRC, 2015 IBC, 2014 NEC, and 2015 UPC; it is not itself a complete code compilation.
    “This Residential Above-Ground Swimming Pool Checklist is based on St. Louis County’s (SLCO) policies, construction codes amended and adopted by ordinance.”
    One more reviewed finding on this topic
    • Adopted (with conditions) — Residential above-ground pool, spa, and hot-tub work addressed by St. Louis County's checklist.
      “2015 International Building Code (IBC) and Ordinance #27,654-Ch.1116\5 (“B” references). 2014 National Electrical Code (NEC) aka NFPA 70 and Ordinance #27,430-Ch.1102 (“E” refs). 2015 Uniform Plumbing Code (UPC) and Ordinance #27,424-Ch.1103 (“P” references).”
  • InspectionsRequired

    Field construction or installation requirements for residential above-ground pools, spas, and hot tubs.

    • Some code requirements are verified through the county inspections process and may not appear fully in drawings.
    • A preconstruction site inspection consultation is required before permit issuance for the covered work and carries an additional fee.
    • The source does not establish the complete inspection schedule for all residential construction.
    “Notice: There will be a preconstruction site inspection consultation before permit issuance. There is an additional fee for this extra inspection. [...] Many code requirements are met through St. Louis County Inspections of field construction or installation.”
  • Certificate of occupancyLimited

    Certificate of completion for an above-ground pool, spa, or hot tub subject to the county checklist.

    • The county inspector will not issue the certificate until the barrier has been provided and inspected for compliance with approved permit materials.
    “Notice: The barrier is a required, integral part of the pool’s* permit; it can’t be separated or removed from the pool* permit. An Inspector shall not issue a certificate of completion for the pool until barrier requirements have been provided and inspected for compliance with the approved permit sets of drawings and documents.”
  • County-wide zoningPresent (with conditions)

    Zoning approval for proposed residential construction in unincorporated St. Louis County.

    • The cited source addresses an above-ground pool, spa, or hot-tub permit and does not establish that county zoning applies inside incorporated municipalities.
    • Where the property is in a municipality, municipal zoning approval is required instead.
    “Where the property is in Unincorporated St. Louis County: Submit electronic site plans drawn to a scale that include the following information: Lot lines drawn. North arrow provided. Dimension and label any setbacks and easements.”
    One more reviewed finding on this topic
    • Present (with conditions) — Zoning regulation administered by St. Louis County in unincorporated St. Louis County.
      “Zoning approval of the proposed new work must be provided with the permit application as follows: [...] Where the property is in Unincorporated St. Louis County: Submit electronic site plans drawn to a scale”
  • Local zoningVaries (with conditions)

    Aggregate county result for zoning administered by St. Louis County in unincorporated areas and by municipalities within the county.

    • The county aggregate does not mean St. Louis County administers every local ordinance.
    • Municipal residents must comply with municipal zoning and other local ordinances.
    • Subdivision indentures may impose additional private restrictions.
    “Where the property is in a Municipality: Submit electronic site plan(s) that have been stamped-approved, signed and dated by the Municipality’s Zoning Officer. [...] Where the property is in Unincorporated St. Louis County: Submit electronic site plans drawn to a scale”
    One more reviewed finding on this topic
    • Varies (with conditions) — Aggregate of zoning administration: municipalities use municipal zoning approval, while unincorporated areas use St. Louis County zoning review.
      “Where the property is in a Municipality: Submit electronic site plan(s) that have been stamped-approved, signed and dated by the Municipality’s Zoning Officer. [...] Where the property is in Unincorporated St. Louis County: Submit electronic site plans drawn to a scale that include the following information:”
  • SetbacksSpecified

    Setbacks for the covered above-ground pool, spa, or hot-tub permit in unincorporated St. Louis County.

    • Site plans must dimension and label setbacks and easements.
    • The source does not state the general numeric setback values for all residential structures.
    “Where the property is in Unincorporated St. Louis County: Submit electronic site plans drawn to a scale that include the following information: Lot lines drawn. North arrow provided. Dimension and label any setbacks and easements.”
  • 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.”
  • Septic inspectionLimited

    Properties with septic systems seeking an above-ground pool, spa, or hot-tub permit in unincorporated St. Louis County.

    • Review and approval by Plumbing Inspections is required before the pool permit is issued.
    • This claim does not establish the inspection rule for septic-system installation or repair.
    “Where applicable, show location/area of existing septic system. Notice: Properties with septic systems will require review and approval by Plumbing Inspections before the permit will be issued. Notice: Properties in a Flood Hazard Area will require flood plain plan review and approval of the pool and its location before the permit will be issued (SLCO Revised Ordinance R322.1).”
  • Driveway accessRequired

    Construction access for the covered permitted work when the existing driveway entrance is unavailable or no driveway exists.

    • A separate permit from the owner of the right-of-way, either the county highway department or municipality, is required for a temporary entrance.
    • Permit issuance does not automatically authorize construction access.
    “Permit issuance for the project does not automatically authorize construction access to that project site. If a project site’s driveway entrance is unavailable for construction access or none exists, the property owner or authorized Contractor must apply for a permit with the Owner of the Right-of-Way (the County’s Highway Dept. or the Municipality) to construct a temporary entrance.”
    One more reviewed finding on this topic
    • Limited — Construction access for the above-ground pool, spa, or hot-tub project addressed by the county checklist.
      “Permit issuance for the project does not automatically authorize construction access to that project site. If a project site’s driveway entrance is unavailable for construction access or none exists, the property owner or authorized Contractor must apply for a permit with the Owner of the Right-of-Way (the County’s Highway Dept. or the Municipality) to construct a temporary entrance.”
  • Building in a floodplainRequired

    Pool location and construction in a flood hazard area.

    • Flood-plain plan review and approval must occur before permit issuance.
    • The source cites SLCO Revised Ordinance R322.1.
    “Notice: Properties in a Flood Hazard Area will require flood plain plan review and approval of the pool and its location before the permit will be issued (SLCO Revised Ordinance R322.1).”
    5 more reviewed findings on this topic
    • Required — 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 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.”
    • Limited — Residential construction and pool development in flood-hazard areas in unincorporated St. Louis County.
      “Notice: Properties in a Flood Hazard Area will require flood plain plan review and approval of the pool and its location before the permit will be issued (SLCO Revised Ordinance R322.1).”
    • Limited — Above-ground pool, spa, or hot-tub development in a Flood Hazard Area in unincorporated St. Louis County.
      “Where applicable, show location/area of existing septic system. Notice: Properties with septic systems will require review and approval by Plumbing Inspections before the permit will be issued. Notice: Properties in a Flood Hazard Area will require flood plain plan review and approval of the pool and its location before the permit will be issued (SLCO Revised Ordinance R322.1).”
    • Required — Use or development in the St. Louis County FP Flood Plain District involving a man-made change to real property below the flood elevation, including construction or erection of a building or structure, filling, grading, paving, mining, dredging, excavation, or drilling.
      “Prior to any use or development of property pursuant to the permitted or conditional uses designated in this district, if such use or development involves man-made change to real property below the flood elevation, including construction or erection of any building or structure, or any filling, grading, paving, mining, dredging, excavation or drilling, the following procedure shall be complied with: (1) The property owner or user shall submit to the Department of Transportation and Public Works [Highways and Traffic] a development plan.”
    • Limited — Development or use involving encroachment into the St. Louis County FP Floodway, including fill, new construction, or material improvement of an existing structure.
      “All development or use of the Floodway is prohibited involving any encroachment, including fill, new construction or material improvement of any existing structure unless certification by a registered professional engineer is provided to and approved by the Department of Transportation and Public Works [Highways and Traffic] that the development will not result in any increase in flood levels during occurrence of the base flood discharge. If and only if this subsection is complied with, use or development of the floodway may be carried out subject to the restrictions of the remainder of this section.”
  • Permit processPartial

    Permit application process for above-ground pools, spas, and hot tubs.

    • Electronic application, zoning approval/site plans, construction-ready drawings, and additional documentation are required as applicable.
    • Municipalities, fire districts, electrical companies, sewer districts, and subdivision trustees may impose additional or more restrictive requirements.
    “Submittal Requirements: Zoning Approval, Construction-Ready Drawings and Their General Notes of Construction Electronic Swimming Pool Permit Application – fill it out, sign and date.”
    One more reviewed finding on this topic
    • Partial — Above-ground pool, spa, or hot-tub permit applications under the county checklist.
      “Electronic Swimming Pool Permit Application”

Missouri rules that apply here

  • Zoning districtsPartial

    Missouri statutory authority for counties to create zoning districts in unincorporated territory; this does not establish or publish the actual zoning districts for any particular county.

    • The statute applies to unincorporated territory of counties subject to sections 64.211 to 64.295.
    • Actual district boundaries, regulations, and maps depend on county adoption and are not supplied by this statewide statute.
    • District regulations must be uniform for each class or kind of building or land use within each district, although regulations may differ between districts.
    • The regulations must be made in accordance with a comprehensive plan.
    “the unincorporated territory may be divided into districts of such number, shape and area as may be deemed best suited”
  • 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.”
    One more reviewed finding on this topic
    • Allowed (with conditions) — Use of onsite wastewater treatment systems as off-grid sanitation where central sewer service is unavailable in Missouri.
      “In Missouri, where central sewer service is not available, homeowners and small business owners use various types of onsite wastewater treatment systems (OWTS).”
  • Well permitLimited

    Construction or alteration of a public well serving a Missouri public water system.

    • Public water systems must receive written approval from the Missouri Department of Natural Resources Public Drinking Water Branch before constructing or altering a public well.
    • The requirement does not apply when the system meets the charitable-and-benevolent-organization exemptions in section 640.116, RSMo.
    • Anyone proposing to install a public well must contact the department’s regional office for a well-site survey.
    • The survey addresses minimum isolation or setback distances from known or potential contaminant sources, including septic tanks, sanitary sewer lines, and landfills.
    • Before applying for construction authorization, the public water system must obtain an estimated casing-depth letter from the Missouri Geological Survey Water Resources Center.
    • There is no fee for the well-site-survey and estimated-casing-depth-letter services.
    • Failure to obtain construction authorization may result in approval delays and possibly require the owner to properly plug the well and drill a new one according to 10 CSR 60-3.

    public water system threshold: at least 15 service connections or regularly serves an average of at least 25 individuals daily, at least 60 days per calendar year

    “Public water systems must receive written approval from the PDWB before constructing or altering a public well”
    3 more reviewed findings on this topic
    • Required — 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 in Missouri.”
    • Required — A person or contractor conducting regulated work to drill, construct, repair, reconstruct, plug, or install pumps or pumping equipment in a water well, heat-pump well, monitoring well, or related well in Missouri.
      “A non-restricted permit is required to drill, construct, repair, reconstruct, plug, or install pumps or pumping equipment in a well.”
    • Limited — Construction or repair of water wells, installation or replacement of pumps, and associated plumbing and electrical work in Missouri.
      “A non-restricted water well installation permit is required to construct or repair a water well in Missouri.”
  • Agricultural exemptionAvailable (with conditions)

    Farm buildings and farm structures used for agricultural purposes under the county building and land-use restriction provisions of RSMo sections 64.800 to 64.905.

    • The exemption does not apply within incorporated portions of counties.
    • The exemption applies to raising crops, livestock, orchards, or forestry and to specified rice-farming or flood-irrigation impoundments.
    • For farm buildings or farm structures, the area must not be within the area shown on the flood hazard area map.
    • The statute preserves the validity of county ordinances or orders adopted before March 4, 1991.
    • Other laws and local requirements may still apply.

    rice-farming or flood-irrigation berm height: <= 18 inches (small berms placed around a field to hold water for growing rice or flood irrigation)

    “This section shall not apply to the erection, maintenance, repair, alteration or extension of farm buildings or farm structures used for such purposes in an area not within the area shown on the flood hazard area map.”
    4 more reviewed findings on this topic
    • Available (with conditions) — Erection, maintenance, repair, alteration, or extension of farm buildings or farm structures as against county fire-protection or fire-prevention ordinances.
      “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.”
    • Available (with conditions) — Erection, maintenance, repair, alteration, or extension of farm buildings or farm structures used for agricultural purposes under RSMo section 64.890, outside incorporated portions of counties and outside areas shown on flood hazard area maps.
      “This section shall not apply to the erection, maintenance, repair, alteration or extension of farm buildings or farm structures used for such purposes [...]”
    • Available (with conditions) — Farm buildings and farm structures statewide, with respect to county fire-protection and fire-prevention ordinances.
      “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 [...]”
    • Available — Erection, maintenance, repair, alteration, or extension of farm buildings or farm structures with respect to county fire-protection or fire-prevention ordinances.
      “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.”
  • Subdividing landLimited

    Subdivision plats in the unincorporated areas of counties covered by RSMo section 64.070 after the county commission adopts subdivision regulations.

    • The county commission must first adopt subdivision regulations.
    • The plat must first be submitted to the planning commission.
    • If the county planning commission does not report upon the plat within thirty days, it may then be deemed approved.
    • If amended or rejected by the planning commission, the action may be overruled and the plat approved only by the county commission, with the reasons for overruling spread upon the county commission minutes.
    • The recorder of deeds may not record the plat until receiving a certificate of authority from the county zoning enforcement officer.
    • The statute also permits a county planning commission, upon written request of an incorporated area's legislative body where there is no municipal planning commission, to pass upon subdivision plats within that incorporated area; those plats are subject to county planning commission rules and approval procedures.

    planning commission reporting period: 30 days (If no report is made, the plat may then be deemed approved.)

    “After the county commission shall have adopted such subdivision regulations, no plat of a subdivision of land within the unincorporated area of such county [...]”
    One more reviewed finding on this topic
    • Limited — Subdivision regulations adopted by Missouri cities, towns, or villages under RSMo section 89.410.
      “The planning commission shall recommend and the council may by ordinance adopt regulations governing the subdivision of land within its jurisdiction.”
  • 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.”
    One more reviewed finding on this topic
    • Published (with conditions) — Missouri onsite wastewater treatment system construction, modification, and repair application fees administered under the statewide DHSS OWTS program.
      “Effective August 28, 2026, [...] the application fees associated with on-site sewage disposal system construction, modifications, and repairs will be temporarily suspended.”
  • county zoning authorityLimited

    Missouri county zoning authority over unincorporated land.

    • RSMo § 64.850 applies to counties of the first class without a charter and counties of the second, third, or fourth class.
    • RSMo § 64.620 applies to counties of the second or third class to which §§ 64.510–64.690 apply.
    • Adoption under §§ 64.510–64.690 requires approval by vote of the people under § 64.530.
    • The authority applies in unincorporated portions and not incorporated portions.
    • The regulations must be in accordance with a comprehensive plan.
    • Under § 64.090, the zoning power does not apply to raising crops, livestock, orchards, or forestry; seasonal or temporary rice-farming or flood-irrigation impoundments; specified farm structures outside mapped flood-hazard areas; or underground mining entered through shafts outside mapped flood-hazard areas.
    • Existing lawful uses and specified public-utility services are protected under the cited statutory schemes.
    “the county commission of any county of the first class not having a charter form of government, or of any county of the second, third or fourth class may, after approval by vote of the people as provided in section 64.845, regulate and restrict, by order of record, in the unincorporated portions of the county, the height, number of stories, and size of buildings, the percentage of lots that may be occupied, the size of yards, courts and other open spaces, the density of population, the location and use of buildings, structures and land for trade, industry, residence or other purposes.”
    2 more reviewed findings on this topic
  • county building authorityLimited

    County authority to regulate residential construction and issue building permits in unincorporated areas of Missouri.

    • The authority under sections 64.170 to 64.200 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 one under those sections.
    • Only voters in the area affected by the proposed code may vote; incorporated-territory citizens cannot vote on a code affecting a county.
    • The county commission must hold at least three public hearings and provide the statutory newspaper publication and county posting notices before adoption.
    • Regulations adopted under section 64.180 apply to unincorporated territory, except as otherwise provided.
    • Adopted or amended codes after August 28, 2001, must use a current, calendar year 1999 or later edition of a nationally recognized building code, as amended.
    • A county building ordinance may not conflict with liquefied petroleum gas installations governed by section 323.020.

    public hearings before adoption: >= 3 hearings minimum (Section 64.180(3)) · newspaper notice: >= 15 days (Notice of hearing time and place must be published in at least two newspapers having general circulation within the county) · posted notice: >= 15 days (Notice must be posted in four conspicuous places in the county) · minimum nationally recognized building-code edition: >= calendar year 1999 edition year (Applies after August 28, 2001, under section 64.180)

    “The regulations adopted shall be applicable to the unincorporated territory of the county, except as otherwise provided herein”
    2 more reviewed findings on this topic
    • Limited — 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.
      “the county commission in all counties of the first and second classification [...] is for this purpose empowered [...] to adopt [...] regulations to control the construction”
    • Limited — Missouri counties' authority to require permits and regulate residential construction in unincorporated areas.
      “Before the adoption of such code of regulations, the county commission shall hold at least three public hearings thereon”

Still unanswered

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

  • Owner-builder exemption — Whether an owner-builder may receive an exemption from County residential building-permit or contractor requirements in unincorporated St. Louis County.
  • Minimum dwelling size — Minimum overall dwelling size in unincorporated St. Louis County.
  • Minimum lot size — Minimum lot size requirements in unincorporated St. Louis County.
  • Lot coverage — Lots in unincorporated St. Louis County.
  • Building height — Structures in unincorporated St. Louis County.
7 more unanswered
  • Living in an RV
  • Camping on your land
  • Tiny homes
  • Manufactured homes
  • Accessory dwellings
  • Mandatory utility hookup
  • 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.

How St. Louis compares in Missouri

Compare side-by-side →See all 115 Missouri counties ranked →