Williamson County, IL: Owner-Builder Allowed

Williamson County, Illinois requires a building permit for construction, alteration and demolition outside cities, villages and incorporated towns; the Supervisor of Assessments administers the county building permit¹. Inside a city or village, the municipality's own rules apply instead, but septic permits for every Williamson County address come from the Franklin-Williamson Bicounty Health Department, and new private wells also need a well permit^2,3. A countywide zoning ordinance remains unconfirmed, but land division is regulated in unincorporated areas^2,4.

At a glance

Building permit: Required outside cities and villages, via the Supervisor of Assessments¹
Zoning: Unconfirmed; ask the county whether parcel-specific rules apply⁴
Septic permit: Local review by Bicounty Health under Illinois public-health rules²
Owner-builder exemption: Not confirmed; ask before you apply⁵
RVs, house cars & mobile homes: Treated like a house under the county's permit ordinance at 100 sq ft or more¹
Building-permit filing fee: $50 residential, $100 commercial, $200 industrial¹
Private well: A permit is required for new well construction³
Land division: County plat review applies outside municipal limits²

Who to call

Building permits

Williamson County Supervisor of Assessments

Building Permit Application intake and approval for construction, alteration and demolition outside Williamson County's cities and villages, under the county's Building Permit Ordinance

Roads & driveways

Williamson County Highway Department

Review of new or reconstructed entrances, driveways and drainage structures connecting to a county road, as part of the county's building-permit review

2 more officesFloodplain permits · Septic permits

Floodplain permits

Williamson County Floodplain Coordinator

Floodplain approval for building permits on property in a designated Williamson County floodplain, under the county's ordinance regulating development in floodplains

Septic permits

Franklin-Williamson Bicounty Health Department - Environmental Health Division

Private sewage disposal (septic) system review, permitting and inspection for Williamson County, plus private well permits

(618) 993-8111

eh@bicountyhealth.org

8160 Express Drive, Marion, IL 62959

Contact details are copied from each office’s official page and were checked against it on October 10, 2026.

Do you need a building permit in Williamson County, Illinois?

Williamson County, Illinois requires a building permit before construction, alteration or demolition outside its cities, villages and incorporated towns, although the ordinance excludes agricultural buildings on farms, including farm residences¹. The rule covers house trailers, house cars, cabins, manufactured and mobile homes, and portable storage buildings of 100 square feet or more¹. A landowner must file a Building Permit Application with the Supervisor of Assessments and receive written authorization before starting construction, placement, alteration, removal or demolition¹. Illinois leaves building permits and inspections to local government, so the county permit controls in unincorporated Williamson County⁶.

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

The Williamson County Supervisor of Assessments takes Building Permit Applications, while the County Highway Engineer reviews a new or reconstructed entrance from a county road as part of that application¹. Ask the county courthouse in Marion for the Supervisor of Assessments because a current direct telephone number is not listed here. The filing fee is $50 for a residential application, $100 for a commercial application and $200 for an industrial application¹. A project with a restroom, kitchen or other plumbing must also notify the Franklin-Williamson Bi-County Health Department so the sanitary sewage system can be checked¹.

Does Williamson County have zoning?

We could not confirm that Williamson County has adopted countywide zoning, so ask the County Clerk or County Board of Commissioners whether zoning, setbacks, height limits or use restrictions apply to the parcel⁴. Illinois counties may establish setback lines and building-height limits through local zoning districts, but state law supplies no single countywide dimensional standard⁷. Zoning uncertainty does not mean land division is unregulated: Williamson County reviews subdivision and land-division plats outside municipal corporate limits². A subdivision within 1.5 miles of a municipality that has the required comprehensive plan and subdivision ordinance also needs municipal approval².

How do septic and well permits work in Williamson County?

Franklin-Williamson Bicounty Health Department reviews and approves new, altered and repaired private sewage systems before construction and issues permits for new systems and major renovations.

Franklin-Williamson Bicounty Health Department reviews and approves new, altered and repaired private sewage systems before construction and issues permits for new systems and major renovations⁸. Contact Environmental Health at 8160 Express Drive, Marion, Illinois, (618) 993-8111 or eh@bicountyhealth.org⁸. Illinois requires sewage-plan approval before installation and notice to the approving authority at least 48 hours before work begins⁹. Only 8.5% of Williamson County soils avoid a severe limitation rating for conventional drain fields, so establish septic feasibility early¹⁰. New private water wells also require plan review, a permit and inspection through the state-local health program; the available rule does not specify a county fee or timing requirement³.

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

Williamson County requires a building permit to place a house trailer, house car, cabin, manufactured home or mobile home of 100 square feet or more outside a city, village or incorporated town.

Williamson County requires a building permit to place a house trailer, house car, cabin, manufactured home or mobile home of 100 square feet or more outside a city, village or incorporated town¹. That permit rule does not answer whether long-term RV or tiny-home occupancy is allowed, and we could not confirm a county rule that does; ask the Supervisor of Assessments and the County Clerk before buying or moving a unit onto land⁴. A manufactured-home community with 5 or more sites needs an Illinois Department of Public Health license, and a manufactured home moved since 1980 must use securing equipment that meets state standards¹¹. State campground licensing likewise does not create a right to live in an RV on a private parcel¹².

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

Ask the County Clerk or County Board whether zoning or local use limits apply to the parcel.

Ask the County Clerk or County Board whether zoning or local use limits apply to the parcel⁴.
Confirm septic feasibility and obtain approval from Franklin-Williamson Bicounty Health Department; obtain a new-well permit too if the property will use a private well^3,8.
File the Building Permit Application with the Supervisor of Assessments; a complete application has a 5-business-day review period¹.
Send any new or reconstructed county-road entrance through County Highway Engineer review¹.
Obtain Floodplain Coordinator approval or a County Board variance if the property is in a designated floodplain¹.
Pay the $50 residential filing fee after approval to receive the permit¹.
Ask Williamson County what final inspection or occupancy documentation it requires because Illinois does not issue the local certificate of occupancy⁶.

What to check before you buy or divide land in Williamson County

Williamson County regulates subdivision and land division outside municipal limits, and grading or other subdivision construction cannot begin before ordinance compliance and preliminary-plat approval². Submit the preliminary plat to the Plat Officer, County Engineer and, when on-site sewage is planned, Franklin-Williamson Bi-County Health Department at least 30 days before the County Board meeting². The final plat is due within 1 year after preliminary approval and normally at least 5 working days before the Board meeting². A subdivision plat must state whether any land lies in a FEMA special flood hazard area². For subdivision access, driveway culverts must be at least 12 inches in diameter; a span over 10 feet needs County Engineer approval, and state-highway access also needs IDOT acceptance and a highway permit².

Watch-outs

A $25 review fee applies per subdivision or survey document, while subdivision-plat compliance review is $50; recording charges and additional statutory amounts are separate, so confirm the current total before filing².
We could not confirm an owner-builder exemption from Williamson County's building-permit requirement, so ask the Supervisor of Assessments before planning to act as your own contractor⁵.

Sources

12 official pages, each quoted and re-checked · written October 10, 2026

Written October 10, 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 Williamson County means bringing your own water and power. The kit we’d start with:

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Compared with neighboring counties

Unlike 4 of its 6 neighbors, Williamson County requires a building permit for a home.

Rule	Williamson County	Johnson County	Franklin County	Saline County	Jackson County	Union County	Hamilton County
Building permit	Required	Limited	Required	Not required	Not required	Required	Not required
County zoning	Not published	Not published	Not published	No	No	Not published	No
Septic permits	Franklin-Williamson Bicounty Health Dept.	Southern 7 Health Dept.	Franklin-Williamson Bicounty Health Dept.	Egyptian Health Dept.	County Health Dept.	Southern Seven Health Dept.	County Health Dept.

Cities and towns in Williamson 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 Bush · Village of Cambria · Carterville · Village of Colp · Creal Springs · Village of Energy · Village of Freeman Spur · Hurst · Johnston City · Village of Pittsburg · Village of Spillertown

Answers from the rulebook for Williamson County

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

Williamson County rules

Minimum lot sizeSpecified
Lots in subdivisions governed by the Williamson County Subdivision Ordinance.
- A minimum lot size of one acre applies unless the subdivision is serviced by an approved publicly owned sewage disposal system.
- The ordinance allows a minimum lot size of 0.25 acre when the stated public-sewer exception applies.
- The cited provision also requires minimum street frontage of 75 feet, or 40 feet for lots around cul-de-sacs when sufficient building space is provided.
minimum lot size without approved public sewage disposal: >= 1 acre (unless the subdivision is serviced by an approved publicly owned sewage disposal system) · minimum lot size with approved public sewage disposal: >= 0.25 acre · minimum street frontage: >= 75 feet (40 feet minimum frontage for lots around cul-de-sacs if sufficient space for building is provided)
“Each lot shall contain an area of not less than one (1) acre, unless the subdivision is serviced by an approved publicly owned sewage disposal system, in which case a minimum lot size of 0.25 acre will be allowed. The minimum allowable street frontage is seventy-five (75) feet, and forty (40) feet is the minimum allowable frontage for lots around cul-de-sacs, as long as sufficient space for building is provided.”
Williamson County Subdivision Ordinance ↗Re-checked Oct 6, 2026
One more reviewed finding on this topic
- Specified — Lots in subdivisions outside municipal corporate limits.
  “Each lot shall contain an area of not less than one (1) acre, unless the subdivision is serviced by an approved publicly owned sewage disposal system, in which case a minimum lot size of 0.25 acre will be allowed. The minimum allowable street frontage is seventy-five (75) feet, and forty (40) feet is the minimum allowable frontage for lots around cul-de-sacs, as long as sufficient space for building is provided.”
  Land Division/Subdivision Ordinance of Williamson County, Illinois ↗Re-checked Sep 26, 2026
SetbacksSpecified
Building setback lines for subdivisions outside municipal corporate limits.
- The quoted setback standards are subdivision-planning standards and are not established here as countywide zoning setbacks.
corner setback: >= 25 feet · side setback: >= 10 feet · rear setback: >= 20 feet
“Building set-back lines shall be twenty-five (25) feet minimum on all corners. Corner lots shall be laid out wide enough to permit building space back of the building line of each street. Set-back lines shall be ten (10) feet on lot sides and twenty (20) feet at the back end of lots.”
Land Division/Subdivision Ordinance of Williamson County, Illinois ↗Re-checked Sep 26, 2026
Septic permitRequired
Private sewage disposal systems in Williamson County, within the service area of the Franklin-Williamson Bi-County Health Department.
- The procedure applies to individuals or licensed contractors wishing to install a private sewage disposal system in Franklin and Williamson Counties, Illinois.
- A $150 sewage-permit fee applies to each sewage permit.
- Only a current Illinois-licensed private sewage contractor or the property owner may construct, alter, or repair a private sewage system.
- A site inspection is required before issuance of a permit for homeowner-installed systems.
- The installation application must be completely filled out and submitted to the Health Department for approval before construction begins.
- The application must be signed by the homeowner and/or sewage contractor.
- Homeowners must obtain an NPDES permit from USEPA/IEPA when discharging to waters of the United States as defined in 40 C.F.R. § 122.2.
- A variance request must be submitted with the permit application when necessary and must be signed by the homeowner.
- A 911 address is required on all permit applications.
- After issuance, the Health Department must be notified 48 hours before construction begins.
- Failure to conform to the Private Sewage Disposal Ordinance of Franklin and/or Williamson Counties constitutes a violation and may result in prosecution by the county.
- The department's environmental-health page states that new, altered, and repaired private sewage systems are reviewed and approved before construction, and permits are issued for new and major-renovation systems.
sewage permit fee: 150 USD (for each sewage permit) · pre-construction notification: 48 hours (after permit issuance and before beginning construction)
“New, altered, repaired private sewage systems are reviewed & approved prior to construction. Permits are issued on new & major renovations systems.”
Private Sewage Disposal Procedures ↗Re-checked Oct 6, 2026
One more reviewed finding on this topic
- Limited — Individual private sewage systems in Williamson County subdivisions.
  “The private sewage disposal system must be designed by a licensed engineer and must comply with the Williamson County Private Sewage Disposal Ordinance and any amendments thereto, as well as the regulations of the Illinois Department of Public Health Private Sewage Disposal Licensing Act and Code and any amendments thereto. Individual private sewage systems shall be installed on at least one (1) acre of suitable land [...] When private sewage disposal systems are planned to be utilized, Franklin-Williamson Bi-County Health Department must approve the preliminary plat and sign the final plat.”
  Williamson County Subdivision Ordinance ↗Re-checked Oct 6, 2026
Subdividing landRegulated (with conditions)
Subdivision and re-subdivision of land outside the corporate limits of municipalities in Williamson County.
- No person may change, re-subdivide, rearrange, or divide a lot or parcel except as permitted by the ordinance and the Illinois Plat Act.
- No construction work in a proposed subdivision, including grading, may begin before compliance with the ordinance and approval of the preliminary plat.
- If the subdivision is outside but within 1.5 miles of a municipality with an official comprehensive plan and subdivision ordinance, corporate approval is required in addition to County approval.
- Applications pending on February 14, 2006 are reviewed under the regulations unless preliminary plat approval was obtained before that date.
municipal proximity requiring additional corporate approval: <= 1.5 miles (Applies to a subdivision outside the municipality whose municipality has adopted an official comprehensive plan and subdivision ordinance.)
“outside the corporate limits of any municipality.”
Land Division/Subdivision Ordinance of Williamson County, Illinois ↗Re-checked Oct 4, 2026
2 more reviewed findings on this topic
- Regulated (with conditions) — Subdivision, dedication, or vacation plats lying wholly or partly outside the corporate limits of a city or village in Williamson County.
  “These rules and regulations governing plats and subdivision of land contained herein shall apply to all subdivided land located within the borders of Williamson County, Illinois and outside the corporate limits of any municipality.”
  Land Division/Subdivision Ordinance of Williamson County, Illinois ↗Re-checked Oct 3, 2026
- Regulated (with conditions) — Subdivision and land division outside municipal corporate limits in Williamson County.
  “outside the corporate limits of any municipality.”
  Ordinance Adopting Rules and Procedures Covering Plats, Divisions of Land, Subdivisions, Condominiums, Dedications and Vacations in Williamson County, Illinois ↗Re-checked Oct 3, 2026
Driveway accessRequired
Subdivision access and driveway entrance infrastructure in unincorporated Williamson County.
- All driveway entrance culverts must be at least 12 inches in diameter.
- All crossroad culverts must be at least 15 inches in diameter.
- A culvert or bridge spanning more than 10 feet requires Williamson County Engineer approval.
- When the only direct access to a subdivision is from a state highway or roadway, an additional IDOT certificate of acceptance is required.
- A highway permit for access from IDOT is required before construction within State rights-of-way.
- The IDOT roadway-access certificate is pursuant to 765 ILCS 205/2 and requires compliance with the Department’s Policy on Permits for Access Driveways to State Highways.
crossroad culvert minimum diameter: >= 15 inches · driveway entrance culvert minimum diameter: >= 12 inches · culvert or bridge span requiring County Engineer approval: > 10 feet
“All crossroad culverts shall be not less than fifteen (15) inches in diameter. All driveway entrance culverts shall not be less than 12” in diameter. The design of any culvert or bridge having a span of more than ten (10) feet must be approved by the Williamson County Engineer.”
Land Division/Subdivision Ordinance of Williamson County, Illinois ↗Re-checked Oct 3, 2026
One more reviewed finding on this topic
- Limited — Driveway and road access for property and subdivision development in unincorporated Williamson County.
  “However, a highway permit for access is required of the owner of the property prior to construction within State rights-of-way.”
  Highway Department ↗Re-checked Oct 3, 2026
Building in a floodplainRequired
Subdivision plats outside municipal corporate limits under the Williamson County subdivision ordinance.
- The subdivision ordinance requires a surveyor statement identifying whether any part of the property is within a Special Flood Hazard Area identified by FEMA.
- The required certificate states that no portion of the parcel may be located in the Special Flood Hazard Area shown for Williamson County on the FEMA Flood Insurance Rate Map.
- The form identifies FEMA Flood Insurance Rate Map Panel No. ______ dated August 17, 1979.
- For subdivisions outside corporate limits but within 1.5 miles of a municipality with an adopted comprehensive plan, the ordinance's sample certificates also require that no part of the subdivision be in the special flood hazard area identified for that city and that no lot be within a surface drain or watercourse serving a tributary area of 640 acres or more.
- The ordinance applies outside municipal corporate limits; municipal corporate approval may additionally be required within 1.5 miles where the stated municipal-plan conditions apply.
tributary area threshold: >= 640 acres (Applies to the additional city-proximity certificate language.) · FEMA map date stated in certificate: August 17, 1979
“These rules and regulations governing plats and subdivision of land contained herein shall apply to all subdivided land located within the borders of Williamson County, Illinois and outside the corporate limits of any municipality. However, if a subdivision of land is located outside, but within 1 ½ miles of, any municipality having adopted an official comprehensive plat and ordinance regulating the subdivision of land, corporate approval shall be required in addition to County approval.”
Land Division/Subdivision Ordinance of Williamson County, Illinois ↗Re-checked Oct 4, 2026
One more reviewed finding on this topic
- Limited — Subdivision plats in Williamson County; the official source establishes a flood-hazard-area statement or certificate requirement, not a general floodplain-development permit determination.
  “The subdivision plat must have a statement from the Professional Land Surveyor indicating whether any part of the property as shown on the map or plat of subdivision is located within a special Flood Hazard Area as identified by the Federal Emergency Management Survey.”
  Land Division/Subdivision Ordinance of Williamson County, Illinois ↗Re-checked Oct 3, 2026
Permit feesPublished (with conditions)
County subdivision and boundary/tract survey review and recording in Williamson County.
- Fees are stated in the ordinance and may be supplemented by additional amounts required by law.
- Subdivision applications must be submitted within the Article V timeline.
- The Plat Officer has five working days under normal conditions to affix a compliance stamp or indicate non-compliance for land divisions covered by the cited provision.
one-time review fee per document: 25 USD (Paid at application submittal before review begins.) · expedited 24-hour review: 75 USD (Within working hours.) · expedited 48-hour review: 55 USD (Within working hours.) · second or re-review of land division: 10 USD · annexation or vacation review: 25 USD · subdivision plat compliance review: 50 USD · subdivision approval/recording fee per plat: 199 USD (Collected by Recorder of Deeds.) · automation fee: 44 USD (The ordinance prints “four dollars ($44.00)”.) · GIS fee: 14 USD · stated total: 217 USD (Plus an additional $10.00 pursuant to the Rental Housing Support Program Act and any additional amounts required by law.)
“The Recorder of Deeds shall also charge an additional four dollars ($44.00) for automation fee and fourteen dollars ($14.00) GIS fee, for a total of Two Hundred Seventeen dollars ($217.00), plus an additional $10.00, pursuant to State of Illinois Senate Bill 75, (Rental Housing Support Program Act), and any additional amounts as may be required by law.”
Land Division/Subdivision Ordinance of Williamson County, Illinois ↗Re-checked Oct 3, 2026
Permit processPublished (with conditions)
Preliminary and final subdivision plat processing outside incorporated city or village limits in Williamson County.
- A preliminary plat must be submitted to the Plat Officer, County Engineer, and Franklin-Williamson Bi-County Health Department where applicable.
- The Health Department submission and approval apply when an on-site waste disposal system is utilized.
- A preliminary plat must be presented at least 30 days before the County Board meeting at which approval is considered.
- A preliminary plat is officially submitted only after required information and applicable fees are provided; the Plat Officer may reject incomplete filings.
- County Engineer approval of the preliminary plat is not final subdivision approval or acceptance of required improvements.
- After preliminary approval, the final plat must be submitted within one year, and at least five working days before the County Board meeting, extendable by mutual consent.
preliminary plat lead time: >= 30 days (Before the County Board meeting at which approval will be considered.) · final plat submission deadline: <= 1 year (After approval of the preliminary plat and plan.) · final plat meeting lead time: >= 5 working days (Under normal conditions; may be extended by mutual consent of the subdivider and agencies involved.)
“After approval of a preliminary plat and plan, there shall be submitted to the Williamson County Board within one (1) year, a final plat, together with two (2) prints thereof, made in accordance with the preliminary plat. [...] The final plat shall be submitted at least five (5) working days, under normal conditions, prior to the next regular meeting of the Williamson County Board at which the final plat will be considered. This time period may be extended by mutual consent of the subdivider and the agencies involved.”
Land Division/Subdivision Ordinance of Williamson County, Illinois ↗Re-checked Oct 3, 2026

Illinois rules that apply here

Building permitLimited
Privately funded construction in Illinois; the State does not itself issue building permits, while any required permit is addressed by the applicable local government.
- Permit requirements may be imposed and administered by the municipality, village, city, or county having jurisdiction.
- The Illinois Capital Development Board states that statewide building codes became effective 1/1/2025, while local code officials remain the best source for project-specific answers.
statewide building-code effective date: 2025-01-01
“No. If any of these are required, they would be addressed by the unit of local government.”
Illinois Codes FAQ ↗Re-checked Sep 26, 2026
One more reviewed finding on this topic
- Not required — Issuance of building permits by the State of Illinois for privately funded construction.
  “No. If any of these are required, they would be addressed by the unit of local government.”
  Illinois Codes FAQ ↗Re-checked Sep 9, 2026
Owner-builder exemptionConditional
Owner occupants or lessee occupants of single-family residences, and owners of single-family residences under construction for their own occupancy, performing plumbing planning, installation, alteration, or repair in Illinois.
- The exemption is limited to plumbing work on the specified single-family residence; the cited statute does not establish a general owner-builder exemption for all construction trades or a statewide exemption from building permits.
- The plumbing must comply with the minimum standards in the Illinois State Plumbing Code.
- The plumbing is subject to inspection by the Illinois Department of Public Health or by the local governmental unit if it retains a licensed plumber as inspector.
- The owner, owner occupant, or lessee occupant may not employ anyone other than a plumber licensed under the Illinois Plumbing License Law to assist.
- An occupant must have taken possession of and be living in the premises as their bona fide sole and exclusive residence, or, for a residence under construction, expect to take possession and live there as that residence, with current intent to live there for at least 6 months after completion of the plumbing work or, for a residence under construction, at least 6 months after completion of construction.
- Failure to possess and live in the premises as a sole and exclusive residence for 6 months or more creates a rebuttable presumption that the required intent was lacking.
minimum occupancy period: >= 6 months (After completion of plumbing work; for a residence under construction, after completion of construction.)
“Nothing herein contained shall prohibit the owner occupant or lessee occupant of a single family residence, or the owner of a single family residence under construction for his or her occupancy, from planning, installing, altering or repairing the plumbing system of such residence”
HB5913 Enrolled — Illinois Plumbing License Law amendment ↗Re-checked Oct 4, 2026
2 more reviewed findings on this topic
- Conditional — Privately funded construction in Illinois, including projects performed by an owner-builder, as to state-issued building permits, state plan review, state building-code inspections, and state occupancy permits.
  “No. If any of these are required, they would be addressed by the unit of local government.”
  Illinois Codes FAQ ↗Re-checked Oct 4, 2026
- Conditional — Statewide treatment of local plumbing permits and inspections for qualifying owner occupants performing plumbing work on a single-family residence.
  “Nothing contained in this Act shall prohibit any city, town, village, township or county from providing for a Plumbing Inspector or from requiring permits for the installation and repair of plumbing and collecting a fee therefor, but a city, town, village, township, or county that requires a permit for installation and repair of plumbing may not issue that permit without verification that the applicant has a valid plumbing license or that the applicant is the owner occupant of a single family residence that is the subject of the permit.”
  225 ILCS 320/18 — Local regulation; Department standards ↗Re-checked Oct 4, 2026
Building code adoptedPartial
Building-code requirements statewide in Illinois, including residential and commercial construction subject to the Capital Development Board Act baseline requirements.
- Effective 2025-01-01, Illinois requires statewide baseline building-code requirements.
- Local governments may adopt building codes, but they are not required to adopt codes; jurisdictions that do not adopt a code are treated as non-building-code jurisdictions and must follow the applicable state-law baseline requirements.
- For jurisdictions with adopted codes, local codes must regulate structural design at least as stringently as the applicable IRC, IBC, or IEBC baseline.
- Commercial buildings in non-building-code jurisdictions and state-funded buildings are subject to the state-listed codes and qualified-inspection requirements.
- Residential requirements differ depending on whether the jurisdiction has adopted a compliant building code and whether the home purchaser and builder agree to an alternative code.
statewide baseline effective date: 2025-01-01 · local code structural minimum for residential buildings: IRC minimum structural requirements · local code structural minimum for commercial new buildings: IBC minimum structural requirements · local code structural minimum for existing commercial buildings: IEBC minimum structural requirements
“The State of Illinois recently passed legislation (Public Act 103-0510) changing the Capital Development Board Act to require statewide building codes effective 1/1/2025. [...] Commercial buildings in jurisdictions that have not adopted a building code AND state funded buildings. [...] Starting 1/1/25 local codes must regulate the structural design in a manner that is at least as stringent as the IBC© for new buildings or IEBC© for existing buildings. [...] Residential buildings in jurisdictions that have not adopted a building code where agreed to by the home purchaser and home builder. [...] Residential buildings in jurisdictions that have adopted a building code. [...] Starting 1/1/25 local codes must regulate the structural design in a manner that is at least as stringent as the IRC©.”
Illinois Codes ↗Re-checked Sep 9, 2026
One more reviewed finding on this topic
- Adopted — Statewide baseline building-code requirements for residential construction in Illinois, including jurisdictions with and without locally adopted building codes.
  “Please be advised that the State of Illinois recently passed legislation (Public Act 103-0510) changing the Capital Development Board Act to require statewide baseline building codes effective 1/1/2025. Locally adopted building codes must comply with the requirements of the Act.”
  Building Codes and Regulations ↗Re-checked Sep 26, 2026
InspectionsLimited
Privately funded construction statewide in Illinois, as to inspections performed by the State rather than by a local authority having jurisdiction.
- The Illinois Capital Development Board does not perform building-code inspections for privately funded construction.
- If inspections are required, they are addressed by the applicable unit of local government.
- A local municipality or county may be a non-building-code jurisdiction, in which case applicable state baseline requirements and inspection-certification provisions may apply.
“No. If any of these are required, they would be addressed by the unit of local government.”
Illinois Codes FAQ ↗Re-checked Sep 26, 2026
One more reviewed finding on this topic
- Not required — Building-code-compliance inspections performed by the State of Illinois for privately funded construction.
  “No. If any of these are required, they would be addressed by the unit of local government.”
  Illinois Codes FAQ ↗Re-checked Sep 9, 2026
Certificate of occupancyLimited
Occupancy permits or certificates for privately funded construction in Illinois.
- The State does not issue occupancy permits for privately funded construction.
- If an occupancy permit is required, it is addressed by the applicable unit of local government.
“No. If any of these are required, they would be addressed by the unit of local government.”
Illinois Codes FAQ ↗Re-checked Sep 26, 2026
One more reviewed finding on this topic
- Not required — Issuance of occupancy permits or certificates by the State of Illinois for privately funded construction.
  “No. If any of these are required, they would be addressed by the unit of local government.”
  Illinois Codes FAQ ↗Re-checked Sep 9, 2026
Building heightDistrict specific (with conditions)
County zoning districts outside municipalities with municipal zoning ordinances.
- The applicable county zoning ordinance determines the actual height limit by district or use.
- No single statewide height measurement was identified.
“including height of buildings and structures”
55 ILCS 5/5-12001 — Authority to regulate and restrict location and use of structures ↗Re-checked Sep 9, 2026
Manufactured homesAllowed (with conditions)
Occupancy of manufactured homes as dwellings, including occupancy in manufactured home communities regulated by IDPH.
- Manufactured home communities with 5 or more sites must be licensed by IDPH, except communities located in home rule units.
- IDPH annually inspects licensed communities for renewal, including water, sewage disposal, electrical systems, lighting, roads, spacing of homes, and garbage disposal.
- Manufactured homes moved since January 1, 1980 must be secured using equipment meeting IDPH standards.
- Effective December 31, 2001, manufactured homes must be installed by an Illinois licensed manufactured home installer or the homeowner and installed according to manufacturer instructions; if unavailable, the IDPH Manufactured Home Installation Code applies.
- Local zoning, building, floodplain, and utility requirements may also apply.
manufactured home community license threshold: >= 5 sites (Communities located in home rule units are excepted from this IDPH licensing statement.) · moved-home tiedown requirement effective date: >= 1980-01-01 · installation requirement effective date: >= 2001-12-31
“designed and situated so as to permit its occupancy as a dwelling place for one or more persons”
Manufactured & Modular Homes/Mobile Structures ↗Re-checked Sep 9, 2026
Who permits septicMixed
Installation and plan approval for private sewage disposal systems statewide in Illinois.
- IDPH regulates private sewage disposal systems within the described scope.
- About 90 local health agencies also review construction plans under local ordinances or as agents of IDPH.
surface discharge threshold: <= 1500 gallons per day (Systems with no surface discharge are also regulated.)
“There are about 90 local health agencies in Illinois that also review sewage disposal system construction plans”
Private Sewage Disposal ↗Re-checked Sep 9, 2026
One more reviewed finding on this topic
- Mixed (with conditions) — Private sewage disposal systems in Illinois, including Williamson County.
  “Health Department must approve the preliminary plat”
  Private Sewage Disposal ↗Re-checked Oct 3, 2026
Septic inspectionLimited
New and replacement surface-discharging private sewage disposal systems covered by Illinois EPA general NPDES Permit ILG62.
- Coverage under the general permit is limited to eligible dischargers.
- Systems not eligible for general-permit coverage may require an individual NPDES permit.
- Periodic inspection, monitoring, and reporting are required under the permit.
“The permit sets discharge limits and requires periodic inspection, monitoring and reporting.”
Illinois Surface Discharge Permit (ILG62) ↗Re-checked Sep 9, 2026
Off-grid sanitationAllowed (with conditions)
Off-grid disposal of human wastes through privies, portable toilets, recirculation toilets, incinerator toilets, and compost toilets statewide in Illinois.
- Other domestic wastes must be disposed of in a conventional private sewage disposal system.
- Compost toilets may also be used for other organic domestic wastes.
- Privies have construction, capacity, venting, maintenance, and abandonment requirements.
- A privy pit must have a minimum capacity of 50 cubic feet per seat.
- A privy must be pumped when filled to within 18 inches of the bottom of the riser.
- Vault privies are required where groundwater or limestone formations are within 4 feet of the bottom of the pit.
- Recirculating toilets must meet NSF International/ANSI Standard 41 and residuals must go to an approved public or private sewage disposal system.
- Incinerator and compost toilets have separate maintenance and disposal requirements; compost toilets must meet NSF International/ANSI Standard 41.
privy pit minimum capacity: >= 50 cubic feet per seat · privy pumping trigger: <= 18 inches from bottom of riser (Pump when filled to within this distance.) · vault-privy groundwater or limestone separation: < 4 feet from bottom of pit (Watertight, non-metal vaults are required where the condition applies.)
“Privies, portable toilets, recirculation toilets, incinerator toilets and compost toilets are approved for private sewage disposal of human wastes.”
77 Ill. Adm. Code 905.130 Human Waste Disposal ↗Re-checked Sep 9, 2026
Well permitRequired
Construction of a new water well, modification of an existing water well, or sealing of an abandoned water well in Illinois.
- A permit must be obtained from the Illinois Department of Public Health or an approved local health department before work begins.
- The application must use Department or approved local health department forms and include a plan and drawing of the proposed construction.
- The plan must include the lot size, slope, property lines, distances to septic tanks, abandoned wells, property lines, seepage fields, sewers, and other contamination sources; driller license number and name; estimated daily pumping capacity if greater than 100,000 gallons per day; well location; owner name and address; well type; estimated depth; well-use type; and proposed aquifer.
- The permit is void if construction has not commenced within one year after issuance.
- The permit fee for constructing, deepening, modifying, or sealing a water well may not exceed $100.
- The Department will deny a permit request when available information indicates groundwater contamination exceeds Class I groundwater standards, subject to the treatment approval provision in subsection (f)(2).
- The permittee must notify the Department, approved local health department, or approved unit of local government by telephone or in writing at least two days before work begins.
maximum water well permit fee: <= 100 USD · permit commencement deadline: 1 year after issuance (Permit is void if construction has not commenced within that period.) · pre-work notification: >= 2 days (Notification may be by telephone or in writing.)
“A permit to construct a new water well, modify an existing water well or seal an abandoned water well shall be obtained from the Department or approved local health department prior to start of work.”
77 Ill. Admin. Code 920.130, Water Well Permit Requirements ↗Re-checked Sep 26, 2026
2 more reviewed findings on this topic
- Required — New private water-well construction in Williamson County.
  “To ensure the safety of these water supplies, the IDPH and local health departments review water well installation plans, issue permits for new well construction, and inspect wells.”
  Private Water & Closed Loop Wells ↗Re-checked Oct 3, 2026
- Required — New private water-well construction in Williamson County, excluding community water wells.
  “To ensure the safety of these water supplies, the IDPH and local health departments review water well installation plans, issue permits for new well construction, and inspect wells.”
  Private Water & Closed Loop Wells ↗Re-checked Oct 3, 2026
Mandatory utility hookupWater and sewer (with conditions)
Each building in Illinois intended for human habitation or occupancy, where the Illinois Plumbing Code applies to its plumbing-system design or installation.
- Water may be supplied by a public water system, semi-private water system, or private water supply constructed under 77 Ill. Adm. Code 920 or 930.
- Sewage may be connected to a public sewer system or a private sewage disposal system constructed under 77 Ill. Adm. Code 905.
- All installations must also comply with applicable State and local laws, ordinances, rules, regulations, and local codes.
- Individually owned residences sharing a common wall or ownership right with ground-floor access, such as townhouses or rowhouses, are separate buildings and require separate connections; a condominium-association residence may instead use one public-water service line to a centralized manifold or meter room with independent shutoff valves, a main shutoff valve at the property line, and compliance with local water-department or water-authority requirements.
- A private water supply may be interconnected with a public water system only when it is located and constructed under 77 Ill. Adm. Code 920 and 925 and the public system is protected against backflow and back siphonage under Section 890.1130; no physical connection is permitted between a potable-water system and a non-potable-water source.
“Each building [...] shall have a connection to a public water system, [...] and a connection to a public sewer system or private sewage disposal system”
77 Ill. Adm. Code 890.170 — Sewer and/or Water Required ↗Re-checked Nov 4, 2026
Agricultural exemptionAvailable
Agricultural experiences conducted as a secondary use with agricultural production on a farm in Illinois.
- The activity must be agriculture-related, a secondary use in conjunction with agricultural production, and occur on a farm.
- The activity must be open to the public with the intended purpose of promoting or educating the public about agriculture, agricultural practices, agricultural activities, or agricultural products.
- The property’s primary use must be agricultural production.
- The exemption prevents a county from requiring a conditional use permit, special use permit, special exception, or variance; the statute does not state that other applicable State or local requirements are waived.
“a county shall not require a conditional use permit [...] or variance for agricultural experiences on property of which the primary use is agricultural production.”
Public Act 102-0492 — Agricultural Experiences Act ↗Re-checked Nov 4, 2026
Short-term rentalsLimited
Short-term rentals in Illinois where at least one room is rented for fewer than 30 consecutive days and accommodations are reserved in advance, when the hosting platform meets the statutory definition of a re-renter.
- Beginning July 1, 2025, qualifying hosting platforms are subject to Hotel Operators’ Occupation Tax.
- The source establishes tax and registration obligations, not statewide land-use permission; local zoning and licensing may separately apply.
rental period: < 30 consecutive days
“Beginning July 1, 2025, hosting platforms for short-term rentals that meet the definition of “re-renter” are subject to Hotel Operators’ Occupation Tax.”
FY 2025-28, Hotel Operators’ Occupation Tax Updates for Hosting Platforms for Short-Term Rentals ↗Re-checked Sep 9, 2026
Campground & park staysLimited
Operation of a campground providing temporary parking of recreational vehicles in Illinois; this is not a determination of long-term RV occupancy on an individual private parcel outside the statutory campground definition.
- IDPH annually inspects and licenses covered campgrounds.
- A covered campground includes an area where three or more tents, cabins, recreational vehicles, or other shelters are erected and maintained for camping, or where space is provided for camping or temporary RV parking for 10 or more persons for six or more camping days in a calendar year.
- Campgrounds within home-rule units of government are exempt from this State program.
- IDPH inspects water supply and sewage disposal systems, electrical systems, sanitation, food service, and recreational facilities.
- IDPH reviews construction plans for new campgrounds and major expansions or alterations.
- Local zoning and other local requirements may separately apply.
recreational vehicles or other shelters erected and maintained for camping: >= 3 shelters (One alternative branch of the statutory campground definition.) · persons using space for camping or temporary RV parking: >= 10 persons (Applies for six or more camping days during a calendar year.) · camping days: >= 6 days per calendar year (Applies to the 10-or-more-person branch of the statutory campground definition.)
“State law requires the IDPH to annually inspect and license campgrounds in Illinois. The Campground Licensing and Recreational Area Act defines campground as a recreational area where three or more tents, cabins, recreational vehicles or other permanent or non-permanent type shelters are erected and maintained for camping or where space is provided for camping, temporary parking of recreational vehicles or placing of such tents, cabins, recreational vehicles or other permanent or non-permanent type shelters of any kind for 10 or more persons for six or more camping days during a calendar year.”
Youth Camps and Campgrounds ↗Re-checked Nov 4, 2026
2 more reviewed findings on this topic
- Allowed (with conditions) — Overnight camping in Illinois campgrounds subject to the Campground Licensing and Recreational Area Act.
  ““Camping Day” means any 24 hour period or portion thereof during which the participants remain overnight at the site.”
  Youth Camps and Campgrounds ↗Re-checked Sep 9, 2026
- Limited — Temporary camping in covered Illinois campgrounds; this claim does not establish whether camping is allowed on a private parcel outside the statutory campground definition.
  “Campgrounds within home rule units of government are exempt. Staff inspects the water supply and sewage disposal systems, the electrical systems, general sanitation, food service and recreational facilities. IDPH also reviews construction plans for all new campgrounds and for major expansions or alterations of existing ones.”
  Youth Camps and Campgrounds ↗Re-checked Nov 4, 2026
county building authorityLimited
County building-construction and building-code regulation, including residential structures, in counties meeting the statutory population and metropolitan-area conditions.
- The county must have a population not in excess of 1,000,000.
- The county must be located in the area served by the Northeastern Illinois Metropolitan Area Planning Commission.
- Rules are subject to rules or regulations adopted by the State Fire Marshal under the cited gasoline and volatile-oils statute.
- The county must exempt municipalities located wholly or partly within the county when the municipal building code is equal to the county regulation and local authorities are enforcing that municipal code.
- The rules apply throughout the county, but municipalities may establish higher standards.
- The rules do not apply to construction or alteration of buildings or structures used or to be used for agricultural purposes on a tract zoned and used for agricultural purposes.
- The county board must follow the publication and posting requirements in 55 ILCS 5/5-1063.
- Beginning on the effective date of the amendatory Act of the 92nd General Assembly, a county adopting a new building code or amending an existing building code must provide the building-code identification to the Capital Development Board under Section 10.18 at least 30 days before adoption.
- Violations are petty offenses, and enforcement is by an officer designated by county-board resolution.
- The provision expressly authorizes county building-construction and building-code rules, but the opened text does not expressly use the phrase residential building permit requirement.
population threshold: <= 1000000 persons (The county must be located in the area served by the Northeastern Illinois Metropolitan Area Planning Commission.) · pre-adoption identification period: >= 30 days (Applies to a new building code or amendment under the stated amendatory-Act provision.)
“The county board in any county with a population not in excess of 1,000,000 located in the area served by the Northeastern Illinois Metropolitan Area Planning Commission may prescribe by resolution or ordinance reasonable rules and regulations (a) governing the construction and alteration of all buildings and structures and parts and appurtenances thereof and governing the maintenance thereof in a condition reasonably safe from the hazards of fire, explosion, collapse, contagion and the spread of infectious disease”
55 ILCS 5/5-1064 — Buildings in certain counties of less than 1,000,000 population ↗Re-checked Oct 1, 2026
One more reviewed finding on this topic
- General — Illinois counties adopting and enforcing building codes and issuing building permits for residential construction in unincorporated areas, subject to the statewide baseline framework.
  “A municipality or county is not required to adopt building codes. If they do NOT adopt a building code then they are considered a non-building code jurisdiction and section 10.09-1 of the Capital Development Board Act (20 ILCS 3105) applies. If they do adopt a building code(s) then it must comply with section 10.18 of the Capital Development Board Act (20 ILCS 3105).”
  Illinois Codes FAQ ↗Re-checked Sep 26, 2026

Still unanswered

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

County-wide zoning — County zoning in unincorporated Williamson County
Local zoning — Municipal zoning within Williamson County (Marion, Herrin, Carterville, etc.)
Zoning districts — Zoning districts in unincorporated Williamson County.
Minimum dwelling size — Minimum dwelling size in unincorporated Williamson County
Lot coverage — Lot coverage in unincorporated Williamson County.

4 more unanswered

Living in an RV
Camping on your land
Tiny homes
Accessory dwellings

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 Williamson County, Illinois

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

Williamson County scores 62/100 on the Bolthole Index, a solid county profile. Its strengths: manageable long-term carry cost and strong self-sufficiency basics: 48.3″/yr rainfall with little drought.

How much does land cost in Williamson County, Illinois?

Land in Williamson County runs about $4,701 per acre, based on the latest county data.

What is the water situation in Williamson County?

Williamson County gets about 48.3" of rain a year, with severe drought in roughly 3% of years.

How remote is Williamson County?

A representative private-land location has about 66,859 people within a 30-minute drive and 1,691,126 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 Williamson County, Illinois