Washington County, MO: No Building Permit, No Zoning

Unincorporated Washington County, Missouri does not require a general building permit, while Potosi requires building permits for specified construction and structural changes^1,2. Potosi also has municipal zoning, but countywide zoning for unincorporated land could not be confirmed². Septic permits remain separate: the Washington County Health Department administers qualifying systems countywide, subject to city and state jurisdictional exceptions³.

At a glance

Building permit: No general building permit in unincorporated areas; Potosi requires building permits for specified work^1,2
Zoning: Potosi has municipal zoning; countywide zoning for unincorporated land could not be confirmed²
Septic permits: Washington County Health Department handles qualifying 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 any^4,5
Farm structures: County fire ordinances cannot require building permits for farm structures; other requirements can still apply⁶
Private wells: Well and pump installers need the applicable state permit; a landowner may do their own work without one⁷
Floodplain development: Some type of permit must be issued for all development in a mapped floodplain, through whichever community participates⁸
Septic exemptions: Most installations and repairs need a permit; confirm any residential-lot exemption before work^3,9

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

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

info@wcmohealth.org

520 Purcell Drive, Potosi, MO 63664

Contact details are copied from each office’s official page and were checked against it on October 7, 2026.

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

A general building permit is not required for a home in unincorporated Washington County, Missouri.

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: Potosi requires a written building-permit application before starting a new building, structure, parking lot, or sign, or enlarging or structurally altering one². Potosi's code official may inspect permitted premises before a certificate of occupancy is issued; inspection of other premises requires reasonable cause to believe a violation exists¹⁰. Potosi also requires a certificate of occupancy before a newly erected or structurally altered building is occupied or used². A county fire-protection ordinance cannot require a building permit for farm structures, but that narrow protection does not remove septic permits, floodplain permits, or municipal requirements⁶. We could not confirm a general owner-builder exemption; ask the County Commission and the municipality governing the parcel^4,5.

Who issues building permits in Washington County?

Washington County has no general building-permit process for an unincorporated home, so call the Washington County Commission when the parcel's county contact is unclear.

Washington County has no general building-permit process for an unincorporated home, so call the Washington County Commission when the parcel's county contact is unclear^1,5. Inside Potosi, the city issues building permits for specified construction and structural changes and administers the related certificate of occupancy². Potosi's building-permit and zoning authority does not replace septic review: the Washington County Health Department administers qualifying onsite wastewater systems, with incorporated-area and state-agency exceptions^3,11. The Clerk's Office maintains official documents, issues licenses, and supports County Commission operations, so it can help locate county records or the correct county contact¹². An entrance onto a state highway may need Missouri Department of Transportation approval¹³. Development in a mapped floodplain needs the applicable community's floodplain permit, and work in a regulatory floodway needs an engineering No-Rise Certificate before that permit can issue⁸.

Does Washington County have zoning?

Potosi has zoning for buildings, structures, and land uses inside its corporate limits.

Potosi has zoning for buildings, structures, and land uses inside its corporate limits². We could not confirm countywide zoning for unincorporated Washington County or zoning status in every other municipality, so ask the Washington County Commission and the relevant city before assuming a parcel has no zoning approval requirement^2,5. We also could not confirm county rules for minimum dwelling size, minimum lot size, setbacks, lot coverage, building height, or subdivision; ask about the specific parcel rather than treating silence as permission⁵. Missouri law authorizes counties to adopt zoning, but that authority does not establish Washington County's current rules¹⁴. Potosi zoning stays municipal, while septic permits for qualifying systems remain with the Washington County Health Department subject to incorporated-area and state-agency exceptions^2,3.

How do septic permits work in Washington County?

The Washington County Health Department administers qualifying onsite wastewater treatment systems under a county ordinance that may be stricter than Missouri's minimum standards.

The Washington County Health Department administers qualifying onsite wastewater treatment systems under a county ordinance that may be stricter than Missouri's minimum standards^3,11. Missouri's baseline requires a septic construction permit for a residential property under 3 acres and for every nonresidential system regardless of tract size, but the residential acreage exemption does not apply in every county⁹. Ask the Health Department to confirm whether Washington County recognizes an exemption before installation or repair begins^3,11. Missouri DNR handles specified systems outside ordinary local coverage, including surface discharges, non-single-family lagoons, industrial wastewater, and systems over 3,000 gallons per day³. Only about 2% of Washington County soils lack severe limitations for a conventional drain field, so make septic feasibility an early purchase condition¹⁵. Missouri does not impose a universal sale inspection for every existing system; a buyer, lender, or local rule may still require an evaluation¹⁶.

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.

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. Ask the Washington County Commission about an unincorporated parcel and the governing city about land inside city limits; Potosi applies municipal zoning within its corporate limits^2,5. Building-permit and zoning answers do not settle sanitation: Missouri allows onsite wastewater treatment where public sewer is unavailable, subject to the Washington County ordinance and applicable approvals¹⁷. The Washington County Health Department remains the septic-permit contact for qualifying systems even where a city handles building permits or zoning, subject to incorporated-area and state-agency exceptions^3,11. Before buying for RV or tiny-home use, get separate answers on zoning approval, building permits, septic permits, floodplain permits, and road access from the authority responsible for each.

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

Confirm whether the parcel is unincorporated or inside a city; Potosi requires building permits for specified construction and structural changes.

Confirm whether the parcel is unincorporated or inside a city; Potosi requires building permits for specified construction and structural changes².

Ask the County Commission and any governing city whether zoning approval, setbacks, county-road access review, or a floodplain contact applies^2,5.

Arrange the septic site evaluation early because only about 2% of county soils lack severe limitations for a conventional drain field¹⁵.

Obtain the septic permit from the Washington County Health Department, or confirmation of an exemption or different agency, before installation or repair^3,9,11.

For a private well, use an installer with the applicable state well or pump permit; a landowner may install their own well or pump without that permit⁷.

Secure any state-highway entrance approval and applicable floodplain permit before site work^8,13.

Obtain Potosi's certificate of occupancy when required; an unincorporated home has no general county building permit^1,2.

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 condition.

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 condition¹⁵. 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 drainage¹⁵. Federal land covers about 17.1% of the county, so verify boundaries, legal access, and any neighboring public ownership on the parcel map¹⁵. Check the current flood map because development in a mapped floodplain needs a permit through the applicable community⁸. 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 differ¹⁵.

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 parcel^5,8.
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 regulation⁵.
Potosi has its own zoning, building-permit, inspection, and certificate-of-occupancy rules, while qualifying septic systems remain under the Washington County Health Department subject to jurisdictional exceptions^2,3,10.

Sources

17 official pages, each quoted and re-checked · written October 7, 2026

Written October 7, 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.

Off-grid gear

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

These are affiliate links — we may earn a commission, at no cost to you. As an Amazon Associate, Bolthole Index earns from qualifying purchases.

Compared with neighboring counties

Rule	Washington County	St. Francois County	Crawford County	Jefferson County	Iron County	Ste. Genevieve County	Dent County
Building permit	Not required	Required	Not required	Required	Not required	Required	Not required
County zoning	No	Not published	No	Yes	Not published	Not published	No
Septic permits	County Health Dept.	County Health Center	County Health Dept.	County Code Enforcement Div.	DHSS	County Health Dept.	DHSS

Cities and towns in Washington 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 covered: Village of Caledonia · Irondale · Town of Mineral Point

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.”
Government — City of Potosi, Missouri ↗Re-checked Sep 27, 2026
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.”
OWTS Construction Permit Process ↗Re-checked Sep 27, 2026
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.”
OWTS Construction Permit Process ↗Re-checked Sep 23, 2026
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”
Types of Entrances Requiring Permits ↗Re-checked Sep 11, 2026
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 ↗From the county’s own site, awaiting a second reviewer

Missouri rules that apply here

Building permitLimited
Building permits for construction in Missouri: no statewide permit is shown; first and second classification counties may adopt building regulations and permits if voters have approved
- Authority is an option for county commissions in counties of the first and second classification, not a statewide mandate
- A county that had not adopted a building code before August 28, 2001 needs voter approval, voted only by voters outside incorporated territory
- Municipalities and other counties must be checked locally
- This claim is about the county enabling authority only; the state septic rule (RSMo 701.031) was not used as a building-permit requirement
“the county commission in all counties of the first and second classification, as provided by law, is for this purpose empowered, subject to the provisions of subsections 2 and 3 of this section, to adopt by order or ordinance regulations to control the construction”
RSMo 64.170 County commissions control construction - issue building permits ↗Re-checked Nov 6, 2026
One more reviewed finding on this topic
- Limited — 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.
  “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.”
  RSMo Section 64.003 ↗Re-checked Sep 27, 2026
Owner-builder exemptionAvailable (with conditions)
A property owner installing, modifying, or repairing that owner's on-site sewage disposal system.
- The owner must comply with RSMo 701.025 to 701.059.
- The statute separately provides that an owner need not obtain a permit or contractor registration merely to clean that owner's on-site sewage disposal system.
“Nothing in sections 701.053 to 701.055 shall preclude property owners from installing, modifying or repairing their own on-site sewage disposal system”
RSMo 701.055 — Property owners may install, modify or clean their own on-site sewage disposal system ↗Re-checked Nov 4, 2026
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”
RSMo Section 64.170 ↗Re-checked Sep 11, 2026
2 more reviewed findings on this topic
- Partial — Residential building-code adoption by Missouri counties, particularly construction in unincorporated county territory.
  “the county commission in all counties of the first and second classification [...] is for this purpose empowered [...] to adopt [...] regulations”
  RSMo § 64.170 — County commissions control construction; issue building permits ↗Re-checked Oct 1, 2026
- Partial — County adoption of residential building codes in Missouri, with the resulting regulations applicable to unincorporated territory when adopted under the statutory authority.
  “the county commission in all counties of the first and second classification, as provided by law, is for this purpose empowered”
  RSMo Section 64.170 — County commissions control construction; issue building permits ↗Re-checked Oct 1, 2026
InspectionsLimited
Construction, major modification, or major repair of an on-site sewage disposal system for which RSMo 701.046 requires notice and an application; this is not a general statewide inspection rule for all buildings.
- The city, county, or department must receive notice and an opportunity to inspect before completion.
- A registered contractor must notify the authority before 9:00 a.m. on the day before completion; an unregistered person must notify it before 9:00 a.m. on the second day before completion.
- The system must remain available for a complete inspection under the state standard until 3:00 p.m. on the completion day unless the authority confirms earlier inspection and approval.
- The system may not be closed or completed if inspection finds it does not meet the state standard; the authority must provide conspicuous notice at inspection and written confirmation of the result, or of no inspection, within three working days of completion.
“without providing notice and an opportunity for inspection by the city, county or department as provided in this section.”
RSMo 701.050 — Construction or repair notice, requirements and inspection ↗Re-checked Nov 4, 2026
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”
RSMo Section 64.261 — Zoning districts, creation, regulations ↗Re-checked Oct 5, 2026
Minimum dwelling sizeDistrict specific (with conditions)
Potential county zoning controls on the size of residential buildings in unincorporated portions of first-class counties other than first-class counties without a charter form of government.
- The county commission is authorized to regulate by order in accordance with a comprehensive plan.
- The statute does not state a statewide minimum dwelling-size measurement.
- The statute expressly excludes incorporated portions of counties and identifies additional agricultural, rice-farming, flood-irrigation, farm-structure, and underground-mining exclusions.
“except in counties of the first class not having a charter form of government [...] in the unincorporated portions of the county [...] size of buildings”
RSMo § 64.090 — Planning and zoning powers of county commission ↗Re-checked Nov 4, 2026
SetbacksSpecified
Size of yards, courts and other open spaces in unincorporated portions of second- and third-class counties with county zoning; setbacks left to such counties
- Power exists only for counties to which sections 64.510 to 64.690 apply under section 64.510
- Exercised only after approval by vote of the people as provided in section 64.530
- Must be done by order of record and in accordance with a comprehensive plan
- Applies only to unincorporated portions of the county
- Does not apply to crops, livestock, orchards, forestry, or farm buildings used for such purposes outside the flood hazard area map area
- Existing lawful uses protected; ordinances adopted before March 4, 1991 unaffected
“the size of yards, courts and other open spaces”
RSMo 64.620 Building restrictions - limitations on regulations (second and third class counties) ↗Re-checked Nov 6, 2026
Lot coverageSpecified
Percentage of lots that may be occupied in unincorporated portions of second- and third-class counties with county zoning; lot coverage left to such counties
- Power exists only for counties to which sections 64.510 to 64.690 apply under section 64.510
- Exercised only after approval by vote of the people as provided in section 64.530
- Must be done by order of record and in accordance with a comprehensive plan
- Applies only to unincorporated portions of the county
- Does not apply to crops, livestock, orchards, forestry, or farm buildings used for such purposes outside the flood hazard area map area
- Existing lawful uses protected; ordinances adopted before March 4, 1991 unaffected
“the percentage of lots that may be occupied”
RSMo 64.620 Building restrictions - limitations on regulations (second and third class counties) ↗Re-checked Nov 6, 2026
Camping on your landLimited
Developments where land is sold or leased for camping in recreational vehicles (recreational developments) under the state wastewater rule 10 CSR 20-6.030; this is a wastewater-disposal rule, not a zoning rule on camping generally
- Applies only when land is sold or leased for the purpose of camping in recreational vehicles.
- To qualify as a recreational development, restrictive covenants must prohibit continuous year-round living on the lot, and no cabins or other structures that could be used for year-round residential purposes are allowed.
- Minimum lot size of 20,000 sq ft applies where individual on-site wastewater treatment facilities are used; no reduction from the minimum lot size determined by the geohydrologic evaluation, though a one-half reduction as indicated by the soils report may be allowed.
- Where sewage dump stations provide collection and treatment, they count as centralized collection and treatment.
- The developer must submit a copy of the restrictive covenants with any plans for dump stations or centralized systems.
- Any residential housing development required to obtain department approval must get written approval before sale or lease of any lot or start of construction.
- Rule text says it does not preclude local, municipal, county or other lawful authority from adopting equal or more stringent subdivision, sewer or on-site system regulations.
- Rule was last amended with an effective date of Jan. 30, 2025.
- The state rule does not itself regulate temporary camping on private land outside such developments; that is left to local zoning.
minimum lot size, recreational development with individual on-site wastewater treatment: >= 20000 square feet (one-half reduction per soils report may be allowed; no reduction from geohydrologic evaluation minimum)
“a development is considered recreational when land is sold or leased for the purpose of camping in recreational vehicles. in order to be considered a recreational development, restrictive covenants must prohibit continuous year-round living on the lot and no cabins or other structures will be allowed that could be used for year-round residential purposes.”
10 CSR 20-6 Permits (incl. 10 CSR 20-6.030 Disposal of Wastewater in Residential Housing Developments), Missouri Secretary of State, Code of State Regulations ↗Re-checked Nov 6, 2026
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.”
Onsite Wastewater Treatment System Inspections Versus Evaluations ↗Re-checked Sep 11, 2026
2 more reviewed findings 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.”
  health.mo.gov ↗Re-checked Sep 11, 2026
- Limited — Inspections of existing onsite sewage systems in connection with property sales statewide in Missouri.
  “Missouri Department of Health and Senior Services' (DHSS) rules governing onsite sewage systems cover minimum construction requirements, system inspections at the time of property sales, and requirements for percolation testers and soil evaluators.”
  health.mo.gov ↗Re-checked Oct 1, 2026
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.”
health.mo.gov ↗Re-checked Sep 11, 2026
3 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.”
  health.mo.gov ↗Re-checked Sep 11, 2026
- 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.”
  Onsite Wastewater Treatment ↗Re-checked Sep 27, 2026
- 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).”
  Onsite Wastewater Treatment ↗Re-checked Oct 1, 2026
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”
Who Regulates Water Wells in Missouri? - PUB4001 ↗Re-checked Oct 5, 2026
4 more reviewed findings on this topic
- Limited — Construction, repair, pump installation, or contracted installation of private domestic water wells in Washington County.
  “Landowners may install their own well or pump without a permit pursuant to the above mentioned law and rules.”
  Water Wells - PUB2945 ↗Re-checked Sep 11, 2026
- 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.”
  Water Wells - PUB2945 ↗Re-checked Sep 27, 2026
- 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.”
  Well and Pump Installation Contractor Permitting ↗Re-checked Oct 1, 2026
- 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.”
  Water Wells - PUB2945 ↗Re-checked Oct 5, 2026
Mandatory utility hookupSewer (with conditions)
Missouri state law preserves the authority of specified local governments and districts that own or operate a sewage-collection-and-treatment sewer system to require connection by owners of houses, buildings, or other facilities within that entity's territory.
- This is an authorization for the applicable city, town, village, sewer district, public water supply district, municipality, political subdivision, or district; it is not a statewide mandate that every property connect.
- The entity must own or operate a sewer system providing collection and treatment of sewage.
- The house, building, or other facility must be within the municipality, political subdivision, or district.
- The sewer system must be available.
- The statute identifies sewer districts organized under chapter 204 or chapter 249 and public water supply districts organized under chapter 247 among the entities whose authority is preserved.
“to require the owners of all houses, buildings or other facilities [...] to connect to the sewer system [...] when such sewer system is available.”
Missouri Revisor of Statutes — RSMo § 644.027 ↗Re-checked Nov 4, 2026
Agricultural exemptionAvailable (with conditions)
Agricultural activities and certain farm structures subject to the county building and land-use restriction powers addressed by Missouri Revised Statutes § 64.890, including Washington County to the extent those statutory powers apply.
- The exemption does not apply to incorporated portions of counties.
- The statute excludes the raising of crops, livestock, orchards, or forestry from the referenced county restriction powers.
- Seasonal or temporary impoundments used for rice farming or flood irrigation are excluded; the statute defines these as small berms of no more than eighteen inches high placed around a field to hold water for growing rice or flood irrigation.
- The statute does not apply to erection, maintenance, repair, alteration, or extension of farm buildings or farm structures used for those purposes in an area not within the area shown on the flood hazard area map.
- The statute preserves existing lawful property use and maintenance, judicial review of reasonableness, and authorized public utility services under the listed exceptions.
rice-farming or flood-irrigation berm height: <= 18 inches (The statute defines qualifying small berms as no more than eighteen inches high.)
“The provisions of this section shall not apply to the incorporated portions of the counties, nor to the raising of crops, livestock, orchards or forestry”
RSMo § 64.890 — Building and land use restrictions — exemptions — limitations on use of powers ↗Re-checked Oct 6, 2026
5 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.”
  RSMo Section 64.003 — Farm buildings and farm structures ↗Re-checked Sep 11, 2026
- 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 [...]”
  RSMo Section 64.890 ↗Re-checked Oct 1, 2026
- 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 [...]”
  revisor.mo.gov ↗Re-checked Oct 1, 2026
- 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.”
  RSMo Section 64.003 — Farm buildings and farm structures ↗Re-checked Oct 5, 2026
- Available (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.
  “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.”
  RSMo Section 64.890 — Building and land use restrictions; exemptions ↗Re-checked Oct 5, 2026
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 [...]”
RSMo Section 64.070 ↗Re-checked Oct 1, 2026
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.”
  RSMo Section 89.410 ↗Re-checked Oct 1, 2026
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.”
Laws and Regulations That Might Affect You if You Mine Sand or Gravel From Missouri Streams ↗Re-checked Sep 11, 2026
2 more reviewed findings 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.”
  Floodplain Forms ↗Re-checked Sep 11, 2026
- Required — All development in a Missouri floodplain, administered through the applicable community floodplain permitting process.
  “Regardless, some type of permit MUST be issued for ALL development in the floodplain.”
  Floodplain Forms ↗Re-checked Oct 5, 2026
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.”
Air Construction Permits ↗Re-checked Sep 11, 2026
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.”
  OWTS Construction Permit Process ↗Re-checked Oct 5, 2026
Permit processPublished (with conditions)
Installation or repair of most onsite wastewater treatment systems in Missouri.
- Some single-family residential lots may be exempt from permitting.
- The applicant must determine which agency has permitting authority where the work is being done.
- DHSS permitting may be administered by the DHSS Onsite Program, a local authority under contract, or a local authority via ordinance.
- Work should not begin until a permit has been issued or an exemption has been confirmed.
- DHSS regulates single-family residential systems and onsite or cluster systems treating domestic wastewater flows of 3,000 gallons per day or less that disperse wastewater through soil treatment or absorption systems.
- DNR regulates other systems, including non-single-family lagoons, systems discharging to surface waters, systems over 3,000 gallons per day, and industrial wastewater systems.
- DNR must approve subdivisions, mobile home parks, and campgrounds if OWTS use is planned.
domestic wastewater flow threshold: <= 3000 gallons per day (Systems above this threshold are regulated by DNR when they disperse wastewater through soil treatment or absorption systems.)
“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.”
OWTS Construction Permit Process ↗Re-checked Oct 5, 2026
One more reviewed finding on this topic
- Published (with conditions) — Permit applications for work on Missouri Department of Transportation right-of-way statewide.
  “Contact the Traffic Specialist a minimum of 48 hours prior to beginning work and for all necessary inspections.”
  Permit Process | Missouri Department of Transportation ↗Re-checked Sep 11, 2026
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.”
RSMo § 64.850 — County commission may prescribe zoning regulations ↗Re-checked Oct 1, 2026
2 more reviewed findings on this topic
- General — Missouri counties adopting zoning regulations for unincorporated territory.
  “If a majority of the votes cast is in favor of county zoning, the county commission shall proceed with a program of county zoning”
  RSMo § 64.090 — Planning and zoning powers of county commission ↗Re-checked Sep 21, 2026
- Limited — Missouri county zoning of unincorporated land.
  “counties of the second, third or fourth class may, after approval by vote of the people [...] in the unincorporated portions of the county”
  RSMo § 64.090 — Planning and zoning powers of county commission ↗Re-checked Oct 1, 2026
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”
RSMo Section 64.170 — County commissions control construction; issue building permits ↗Re-checked Oct 1, 2026
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”
  RSMo § 64.170 — County commissions control construction and issue building permits ↗Re-checked Sep 21, 2026
- 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”
  RSMo § 64.170 — County commissions control construction; issue building permits ↗Re-checked Oct 1, 2026

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.”
Chapter Twenty-six: Planning and Zoning ↗Re-checked Sep 27, 2026
One more reviewed finding on this topic
- Required — New buildings, structures, parking lots, signs, and enlargements or structural alterations within the City of Potosi.
  “It shall be unlawful to start the construction of a new building, structure, parking lot, or sign or the enlargement or structural alteration”
  Potosi Code, Chapter 26, Planning and Zoning ↗Re-checked Oct 4, 2026
InspectionsLimited
Inspection authority for dwellings, dwelling units, and premises within the City of Potosi, Washington County, Missouri.
- For a structure or premises for which a permit has been issued but no certificate of occupancy has been received, the code official may enter at any reasonable time.
- For other structures or premises, inspection authority requires reasonable cause to believe that a code violation exists.
- Inspections are subject to constitutional restrictions on unreasonable searches and seizures.
- If entry is refused or not obtained, the code official may pursue recourse as provided by law.
“The code official shall have the authority to enter at any reasonable time any structure or premises for which a permit has been issued but has not received a certificate of occupancy. For all other structures or premises, when the code official has reasonable cause to believe that a code violation exists, the code official is authorized to enter the structure or premises at reasonable times to inspect subject to constitutional restrictions on unreasonable searches and seizures. If entry is refused or not obtained, the code official is authorized to pursue recourse as provided by law.”
Potosi Code, Chapter 5, Buildings ↗Re-checked Oct 6, 2026
One more reviewed finding on this topic
- Limited — Building, structure, and premises inspections conducted by the City of Potosi Building Commissioner under Chapter 26.
  “Inspections may be prompted on the basis of complaint or as part of a systematic inspection program directed by the Building Commissioner.”
  Potosi Code, Chapter 26, Planning and Zoning ↗Re-checked Oct 4, 2026
Certificate of occupancyRequired
Buildings erected or structurally altered, and proposed building or land uses, within the City of Potosi, Washington County, Missouri.
- No building erected or structurally altered may be occupied or used until the building inspector issues a certificate of occupancy.
- The certificate must state that the building or proposed use complies with building and health laws and ordinances and the Potosi regulations.
- A record of certificates is kept by the building inspector; copies are furnished on request to a person with a proprietary or tenancy interest.
- No fee is charged for a certificate of occupancy.
- No excavation permit for a building may be issued before application for a certificate of occupancy.
- Application must be made coincident with the building-permit application.
- The certificate must be issued within ten days after erection or structural alteration is completed in conformity with the regulations.
- A certificate for a legal non-conforming use must state that the use is a legal non-conforming use.
issuance deadline: 10 days (After erection or structural alteration has been completed in conformity with the regulations.) · certificate fee: 0 USD
“No vacant land shall be occupied or used except for agricultural uses and no building hereafter erected or structurally altered shall be occupied or used until the building inspector shall have issued a certificate of occupancy. [...] No fee shall be charged for a certificate of occupancy. No permit for excavation for any building shall be issued before application has been made for certificate of occupancy. [...] Certificate of occupancy shall be applied for coincident with the application for a building permit and shall be issued within ten (10) days after the erection or structural alteration of such building shall have been completed in conformity with the provisions of these regulations.”
Potosi Code, Chapter 26, Planning and Zoning ↗Re-checked Oct 6, 2026
One more reviewed finding on this topic
- Required — A building constructed as or altered into a dwelling in the City of Potosi before human habitation
  “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.”
  Potosi Code, Chapter Five: Buildings ↗Re-checked Sep 11, 2026
Local zoningPresent (with conditions)
Property within the incorporated limits of the City of Potosi, Washington County, Missouri.
- The code divides the City of Potosi into eleven zoning districts.
- District locations and boundaries are shown on the Official Zoning Map incorporated into the article.
- The quoted provision is city-specific and does not establish zoning in unincorporated Washington County or other municipalities.
zoning districts: 11 districts
“The City of Potosi shall be divided into eleven (11) zoning districts, the location and boundaries of which are shown on the Official Zoning Map, which Map is incorporated in this Article by this reference.”
Potosi Code Chapter 26, Article II, Planning and Zoning ↗Re-checked Oct 9, 2026
One more reviewed finding on this topic
- Present (with conditions) — Land within the City of Potosi, Washington County, Missouri.
  “The City of Potosi shall be divided into eleven (11) zoning districts, the location and boundaries of which are shown on the Official Zoning Map, which Map is incorporated in this Article by this reference.”
  Potosi Code, Chapter 26, Article II — Zoning ↗Re-checked Oct 4, 2026

Still unanswered

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

Minimum lot size — Minimum lot size requirements in Washington County, including unincorporated areas.
Building height — Building height requirements in Washington County, including unincorporated areas.
Living in an RV — Long-term or residential RV occupancy on private land in unincorporated Washington County, Missouri
Tiny homes — Occupancy of tiny homes, including tiny houses on wheels, in unincorporated Washington County, Missouri
Manufactured homes — Occupancy and placement of manufactured homes in unincorporated Washington County, Missouri

2 more unanswered

Accessory dwellings
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.

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.

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