Bolthole Index

Washington County, Missouri

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

72Index Score / 100
#49 of 115 in Missouri

Available records indicate that unincorporated Washington County, Missouri does not require a general building permit, but incorporated cities can have their own rules12. Septic is separate: the Washington County Health Department administers permits under a county ordinance that may be stricter than Missouri's minimum standards3.

At a glance

Building permit
Not required in unincorporated Washington County; incorporated cities may have separate rules12
Zoning
Available records indicate no zoning in unincorporated areas; Potosi has zoning inside city limits45
Septic permits
Washington County Health Department handles most OWTS permits under its own ordinance3
Owner-builder
We could not confirm a general owner-builder exemption; ask the County Commission and the municipality, if any67
Farm structures
County fire-protection ordinances cannot require permits for farm buildings, but other requirements can still apply8
Private wells
Contracted well and pump work needs state permits; a landowner may install their own without one9
Floodplain development
Some type of permit must be issued for all development in a mapped floodplain, through whichever community participates10
Septic exemptions
Some single-family lots may be exempt, but Washington County must confirm an exemption before work starts3

Who to call

Also useful

Washington County Commission

County governing body; commissioners meet at the courthouse in Potosi and are the first call for land-use questions since there is no county building or zoning department

573-436-7704

102 North Missouri Street, Potosi, MO 63664

Also useful

Washington County Clerk's Office

County recording, elections and licensing; supports the county commission's operations

573-436-7704

[email protected]

102 North Missouri Street, Potosi, MO 63664

Septic permits

Washington County Health Department, Environmental Health (OWTS)

OWTS (septic) construction permits, the county's soil evaluators list, and registered installer applications for Washington County

573.438.2164

[email protected]

520 Purcell Drive, Potosi, MO 63664

Contact details are copied from each office’s official page and were checked against it on September 28, 2026.

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

Available records indicate that a general building permit is not required for a home in unincorporated Washington County, Missouri1. Confirm the parcel is outside an incorporated city before relying on that answer, because Potosi requires a written application and building permit before specified new construction, enlargement, or structural alteration begins2. Potosi also has separate dwelling-inspection and certificate-of-occupancy rules1112. Missouri's farm-building protection is narrower than a blanket permit exemption: a county fire-protection or fire-prevention ordinance cannot require permits for farm buildings, but septic, floodplain, utility, municipal, and other applicable requirements can remain8. We could not confirm a general owner-builder exemption, so ask the Washington County Commission and any municipality governing the parcel67.

Who do you call in Washington County if there's no building department?

For an unincorporated parcel, call the Washington County Commission first when a building, land-use, county-road access, or floodplain contact is unclear7. The Washington County Clerk's Office maintains official documents, issues licenses, and supports County Commission operations, making it a useful second contact for finding the correct county office or record13. A project inside Potosi follows the city's permit process, not the unincorporated-county answer2. A residential driveway or another entrance connecting to a state highway may need Missouri Department of Transportation approval; the cited entrance list does not establish that MoDOT controls every road in Washington County14. Development in a mapped floodplain needs the applicable community's floodplain permit, and proposed work in a regulatory floodway needs an engineering No-Rise Certificate before that permit can issue10.

Does Washington County have zoning?

Available records indicate no county zoning for unincorporated Washington County, Missouri4. Local zoning still varies by jurisdiction: Potosi's zoning regulations apply to buildings, structures, and land uses inside Potosi's corporate limits, while zoning coverage in other municipalities requires separate confirmation5. We could not confirm Washington County rules for minimum dwelling size, minimum lot size, setbacks, lot coverage, building height, or subdivision, so ask the County Commission about the specific parcel rather than treating silence as permission7. Missouri law gives counties a process for adopting zoning, but that statewide authority alone does not prove Washington County currently administers a zoning program15. Deed restrictions, easements, and utility requirements can also matter to a purchase, so review the parcel's recorded documents with the appropriate professionals.

How do septic permits work in Washington County?

The Washington County Health Department is the local onsite wastewater authority and Washington County has its own OWTS ordinance, which may impose requirements beyond Missouri's minimum standards16. A construction permit is required before installing or repairing most systems; some single-family lots may be exempt, but the Health Department should confirm the exemption before work begins3. Missouri's baseline requires a permit for residential property under 3 acres and for nonresidential systems regardless of tract size, yet that size exemption does not apply in every ordinance county17. Only about 2% of Washington County soils lack severe limitations for a conventional drain field, so make septic feasibility an early purchase condition and expect site-specific evaluation18. State rules do not require an existing system to be upgraded merely because a property is sold, although a buyer, lender, or county rule may still call for an evaluation19.

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

We could not confirm a Washington County rule that either allows or prohibits full-time RV living, temporary camping, a tiny house on wheels, or a tiny home on a foundation. Available records indicate no zoning in unincorporated Washington County, but that does not by itself answer sanitation, utility, floodplain, road-access, deed-restriction, or occupancy questions4. Ask the Washington County Commission about the parcel and ask the governing municipality separately if the land is inside city limits75. An off-grid home may use an onsite wastewater system where public sewer is unavailable, subject to the county ordinance, site and soil conditions, and applicable approval20. Contact the Washington County Health Department before placing or occupying an RV or tiny home if wastewater will be generated onsite321.

What are the steps to build a home in Washington County?

  1. Confirm whether the parcel is unincorporated or inside a city; Potosi requires permits for specified construction and structural changes2.
  1. Ask the County Commission about unresolved land-use, county-road access, and floodplain contacts for the parcel7.
  1. Arrange the septic site evaluation early because only about 2% of county soils lack severe limitations for a conventional drain field18.
  1. Obtain an OWTS permit from the Washington County Health Department, or written confirmation that the lot qualifies for an exemption, before installation or repair begins321.
  1. For a private well, use properly permitted contractors; a landowner installing their own well or pump has a limited state permit exception but must still follow the other rules9.
  1. Secure any state-highway entrance approval and applicable floodplain permit before site work1410.
  1. For an unincorporated home, available records indicate no general building permit requirement1.

What should you check before buying land in Washington County?

Only about 2% of Washington County soils lack severe limitations for a conventional drain field, so make an acceptable site evaluation and septic design a purchase condition18. About 50.7% of the county is at a slope of 15% or less, while 86.2% is wooded; inspect the actual homesite and access route before budgeting for clearing, grading, and drainage2223. Federal land covers about 17.1% of the county, so verify boundaries, legal access, and any neighboring public ownership on the parcel map24. Check the current flood map because development in a mapped floodplain needs a permit through the applicable community10. Washington County's effective property-tax rate is about 0.6%, its median annual property-tax bill is about $682, its typical home value is about $196,763, and farmland averages about $2,926 per acre; parcel-specific assessments can differ25262728.

Watch-outs

  • Call the Washington County Commission to identify who handles access from a county road and which community administers floodplain permitting for a specific parcel710.
  • We could not confirm minimum lot size, setbacks, building height, subdivision, or RV and tiny-home occupancy rules for unincorporated land; ask the County Commission before relying on an assumed absence of regulation7.
  • Potosi has its own zoning and building-permit rules inside city limits, so confirm parcel jurisdiction before using the unincorporated-county answer52.

Sources

  1. State of Missouri - County Building Codes dataset (2026 county census)
  2. Chapter Twenty-six: Planning and Zoning, quoted and re-checked
  3. OWTS Construction Permit Process, quoted and re-checked
  4. Meramec Regional Planning Commission - Washington County (2026 county census)
  5. Government — City of Potosi, Missouri, quoted and re-checked
  6. (2026 county census)
  7. Washington County Commission (washingtoncountymo.us)
  8. RSMo Section 64.003, quoted and re-checked
  9. Water Wells - PUB2945, quoted and re-checked
  10. Floodplain Forms, quoted and re-checked
  11. Potosi Code, Chapter Five: Buildings, quoted and re-checked
  12. Potosi Code, Chapter Five: Buildings, quoted and re-checked
  13. Washington County Clerk's Office (washingtoncountymo.us)
  14. Types of Entrances Requiring Permits, quoted and re-checked
  15. RSMo § 64.090 — Planning and zoning powers of county commission (Missouri statewide rule), quoted and re-checked
  16. OWTS Construction Permit Process, quoted and re-checked
  17. Frequently Asked Questions, quoted and re-checked
  18. Share of soils without severe limits for a conventional septic drain field (USDA SSURGO): Bolthole Index county data
  19. Frequently Asked Questions, quoted and re-checked
  20. Onsite Wastewater Treatment, quoted and re-checked
  21. Washington County Health Department, Environmental Health (OWTS) (wcmohealth.org)
  22. Share of land at 15% slope or less: Bolthole Index county data
  23. Wooded share of land: Bolthole Index county data
  24. Federal land share: Bolthole Index county data
  25. Effective property tax rate: Bolthole Index county data
  26. Median property tax bill: Bolthole Index county data
  27. Typical home value (Zillow): Bolthole Index county data
  28. Farmland value per acre (USDA census): Bolthole Index county data

Written September 28, 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

Washington County in Missouri

72
County map
Washington County highlighted among the Missouri counties · colored by Index score

How Washington County scores

Seclusion69100% ev.
Self-Sufficiency53100% ev.
Admin Boringness8790% ev.
Durability48100% ev.
Property Autonomy47100% ev.
Carry Cost83100% 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 →

$197kTypical home
0.6%Property tax
$2,926Land / acre
45.6"Annual rain
5.5% of yrsSevere drought
12.7 / yr (+11)Mid-century 100°F days
15.2 daysMid-century dry spell
1.98" (+8%)Mid-century 1-day rain
1.83×Wildfire change factor
100%Forward climate coverage
$2,122Home insurance / yr
2.5% / yrInsurance growth
1.55%Nonrenewal rate
county median (2+ published ZIPs)Insurance basis
10,317People within 30 min
1,995,254People within 2 hr
36,196Radius comparison (15 mi)
31People / sq mi
17.1%Federal land
50.7%Land at 15% slope or less
2%Septic soil without severe limits
9,566 acWorkable land screen
86.2%Wooded land
43.6 tonsBiomass / forest ac
55°FAvg temp

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Answers from the rulebook for Washington County

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

Washington County rules

  • Local zoningVaries (with conditions)

    Aggregate local zoning within Washington County; at least the incorporated City of Potosi has municipal zoning, while countywide and other municipal coverage was not established in this search.

    • The Potosi zoning rules apply within the corporate limits of the City of Potosi, not generally to unincorporated Washington County.
    • Other municipalities and any county zoning applicable to unincorporated areas require separate verification.
    “The regulations and restrictions in this Article shall apply to all buildings, structures, and land uses within the corporate limits of the City of Potosi, unless otherwise exempted or grand-fathered by other provisions of this Article.”
  • Who permits septicCounty

    On-site wastewater permitting in Washington County, Missouri, subject to incorporated-area jurisdictional exceptions and the types of systems regulated by state agencies.

    • The Washington County Health Department is identified by Missouri DHSS as the county authority with an ordinance.
    • The county ordinance may impose requirements beyond Missouri minimum construction standards.
    • Missouri DHSS states that some incorporated cities may not fall under a local permitting authority even when a county ordinance is in place; incorporated-area work may be referred back to DHSS.
    • Missouri DNR regulates systems outside DHSS jurisdiction, including systems with flows greater than 3,000 gallons per day, systems discharging to surface waters, non-single-family lagoons, and industrial wastewater systems.

    maximum domestic wastewater flow under DHSS coverage: <= 3000 gallons per day (DNR regulates specified systems outside DHSS coverage)

    “Agency: Washington County Health Dept. Authority Type: Ordinance. Address: 520 Purcell Drive Potosi, MO 63664 County: Washington Phone: (573) 438-2164 Website: www.wcmohealth.org Alert: Contact the agency above for onsite wastewater permitting instructions. This county has their own Onsite Wastewater Ordinance and may have additional requirements beyond the state minimum construction standards.”
  • Septic permitRequired

    Installing or repairing most onsite wastewater treatment systems in Washington County, Missouri, under the Washington County Health Department's onsite wastewater ordinance.

    • The Washington County Health Department is identified by Missouri DHSS as the local permitting agency and Washington County is identified as an ordinance county.
    • Some single-family residential lots may be exempt from permitting; the exemption must be confirmed by the appropriate permitting authority.
    • Washington County may impose requirements beyond Missouri's state minimum construction standards.
    • Work should not begin until a permit has been issued or an exemption to permitting has been confirmed.
    • Some incorporated areas may not fall under the local permitting authority and may be referred back to DHSS.
    • Lagoons serving anything other than a single-family residence, systems discharging to surface waters, systems treating flows greater than 3,000 gallons per day, and industrial wastewater systems are regulated by the Missouri Department of Natural Resources rather than under the ordinary DHSS OWTS coverage.
    “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. [...] Agency: Washington County Health Dept. Authority Type: Ordinance [...] Contact the agency above for onsite wastewater permitting instructions. This county has their own Onsite Wastewater Ordinance and may have additional requirements beyond the state minimum construction standards.”
  • Driveway accessLimited

    Entrance types administered by the Missouri Department of Transportation, including residential driveways, side roads, commercial drives, truck entrances, and paved approaches.

    • The official page identifies permit-required entrance categories but does not state that every road or driveway in Washington County is under MoDOT jurisdiction.
    • Restricted-access entrance configurations may include right-in/right-out, right-in-only, right-out-only, and other listed configurations.
    “Types of Entrances Requiring Permits Typical entrance details Type I: Residential Driveway Type II: Side Road Type III: Commercial Drive Type IV: Truck Pair Type V: Truck Single/Volume Product Paved Appoach”
  • County-wide zoningAbsent

    Washington County does not require permitting for sites outside the city limits of Potosi and has no countywide zoning; land-use controls apply only within incorporated municipalities.

    Meramec Regional Planning Commission - Washington County ↗Scouted from the county site, not yet independently re-checked

Missouri rules that apply here

  • Building permitLimited

    Erection, maintenance, repair, alteration, or extension of farm buildings or farm structures in Washington County, to the extent a county fire-protection or fire-prevention ordinance would otherwise require a permit.

    • RSMo Section 64.003 applies to fire-protection or fire-prevention ordinances adopted by a county; it does not establish that all building permits or permits imposed by other authorities are unnecessary.
    • The statute is effective August 28, 2025.
    “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.”
  • 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.”
    One more reviewed finding on this topic
    • Limited — Inspection or evaluation of existing onsite wastewater systems, especially in connection with a real-estate transaction, in Washington County.
      “State regulations do not require systems to be brought up to current standards as a result of an inspection/evaluation to be sold.”
  • 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.”
    2 more reviewed findings on this topic
    • Limited — Off-grid domestic sanitation and onsite wastewater disposal in Washington County.
      “No. Your system cannot pose a threat to public health or to the environment.”
    • Allowed (with conditions) — Use of an onsite wastewater treatment system where central sewer service is unavailable in Washington County, subject to the county ordinance and applicable state or local approvals.
      “An estimated 25% of homes in Missouri rely on an onsite wastewater treatment system (OWTS) in areas where public sewers are not available. Onsite systems treat wastewater and disperse it on the property where it is generated. [...] When authority is based on a local ordinance, regulation can be more restrictive than the state standard; check with your local authority.”
  • Well permitLimited

    Construction, repair, pump installation, or contracted installation of private domestic water wells in Washington County.

    • A non-restricted water-well installation permit is required to construct or repair a water well.
    • A non-restricted pump-installation permit is required to install or replace a pump and for plumbing/electrical lines from the well to the structure.
    • A restricted water-well or pump-installation permit is required when someone contracts or directs the installation.
    • Landowners may install their own well or pump without a permit, but must comply with all other rules.
    • Wells drilled after July 31, 1987 must be reported by the driller; new-well owners pay a processing fee for review and certification.

    well construction permit: required (Landowners installing their own well may be exempt from permit requirements.) · well installation reporting start date: 1987-07-31 (All wells drilled after this date must be reported by the driller.)

    “Landowners may install their own well or pump without a permit pursuant to the above mentioned law and rules.”
    One more reviewed finding on this topic
    • Limited — Water-well construction or repair in Washington County, including private domestic wells.
      “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 in a water well. A non-restricted pump installation permit is also needed to install or repair the plumbing and electrical lines from the well to the point of entry in the structure. A restricted water well or pump installation permit is required for someone to contract these activities or to direct the installation. Landowners may install their own well or pump without a permit pursuant to the above mentioned law and rules.”
  • Agricultural exemptionAvailable (with conditions)

    Erection, maintenance, repair, alteration, or extension of farm buildings or farm structures in Washington County, including unincorporated areas, to the extent a county fire-protection or fire-prevention ordinance would otherwise regulate or require a permit.

    • The exemption is limited to county fire protection or fire prevention ordinances.
    • The source states an effective date of August 28, 2025.
    • Other requirements not covered by RSMo Section 64.003, including floodplain, septic, utility, or other applicable state or local requirements, were not resolved by this claim.

    effective date: 2025-08-28

    “Effective - 28 Aug 2025 64.003. Farm buildings and farm structures, limitation on certain 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.”
    One more reviewed finding 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.”
  • 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.”
    One more reviewed finding on this topic
    • Required — All development in the floodplain in Washington County, subject to the applicable community floodplain-management process.
      “This sample Floodplain Development Permit was developed by the State and can be used “as is” or modified to fit the community’s permit process. Regardless, some type of permit MUST be issued for ALL development in the floodplain. An Engineering “No-Rise” Certificate is required for all proposed development in the regulatory floodway, and must be obtained by the community before the floodplain development permit may be issued.”
  • 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”

Inside cities and towns in Washington County

Municipal rules found while researching the county. They apply inside that city or town, not to unincorporated land.

  • Building permitRequired

    New buildings, structures, parking lots, signs, and enlargement or structural alteration within the City of Potosi.

    • A written application must be filed and a building permit obtained before starting construction or the stated enlargement or alteration.
    • Applications must comply with the Potosi zoning article and building code.
    • A plat in duplicate, drawn to scale, must be filed in the form prescribed by the Building Commissioner and include required location and other information.
    • Failure to provide required information may justify permit revocation.
    • The Board of Adjustment may issue a written order allowing a permit or certificate of occupancy where the construction, addition, or alteration would otherwise violate the article.
    “It shall be unlawful to start the construction of a new building, structure, parking lot, or sign or the enlargement or structural alteration of a building, structure, parking lot, or sign, without first filing a written application for and obtaining a building permit.”
    One more reviewed finding on this topic
    • Required — Construction requiring a building permit within the City of Potosi
      “Plot plan must be completed on back of this application or attached before permit is issued.”
  • InspectionsLimited

    Buildings containing dwellings, dwelling units, rooming units, temporary housing, or habitable rooms in the City of Potosi, when occupancy, change of occupancy, or ownership is involved

    • The inspection is required before occupancy, change in occupancy, or ownership for the listed residential uses.
    • The cited provision concerns fitness for human occupancy and minimum housing standards, not a general construction-stage inspection schedule.
    “Inspect prior to occupancy, change in occupancy or ownership, any building which shall contain any dwelling, dwelling unit, rooming unit, temporary housing or habitable room, to determine such dwelling, dwelling unit, rooming unit, temporary housing or habitable room is fit for human occupancy, is clean, sanitary, and complies with all provisions of this Chapter with regard to minimum standards for habitation, and is not in a dangerous condition or contaminated by methamphetamine precursor chemicals or methamphetamine production.”
  • Certificate of occupancyRequired

    A building constructed as or altered into a dwelling in the City of Potosi before human habitation

    • The building official must issue a certificate that the dwelling substantially conforms to the act.
    • The certificate is to be issued within 15 days after written application if the dwelling is entitled to it.

    issuance deadline: 15 days (after written application, if the dwelling is entitled to the certificate)

    “No building constructed as or altered into a dwelling shall be occupied in whole or in part for human habitation until the issuance of a certificate by the building official that said dwelling substantially conforms in all respects to the requirements of this act. Such certificate shall be issued within 15 days after written application therefore if said dwelling at the date of such application shall be entitled thereto.”

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 building-permit or contractor requirements in Washington County
  • Zoning districts — Zoning-district publication for Washington County, Missouri.
  • Minimum dwelling size — Minimum dwelling size requirements in Washington County, including unincorporated areas.
  • Minimum lot size — Minimum lot size requirements in Washington County, including unincorporated areas.
  • Setbacks — Building setbacks in Washington County, including unincorporated areas.
10 more unanswered
  • 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 Washington County, Missouri

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

Washington County scores 72/100 on the Bolthole Index, a strong county profile. Its strengths: low administrative friction for a quiet rural property and manageable long-term carry cost.

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

Washington County does not require a county building permit for a home in unincorporated areas, and it has no county-wide zoning. Onsite septic is permitted by Washington County Health 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 Washington County, Missouri?

Land in Washington County runs about $2,926 per acre, based on the latest county data.

What is the water situation in Washington County?

Washington County gets about 45.6" of rain a year, with severe drought in roughly 5.5% of years.

How remote is Washington County?

A representative private-land location has about 10,317 people within a 30-minute drive and 1,995,254 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 Washington County means bringing your own water and power. The kit we’d start with:

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How Washington compares in Missouri

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