Zoning, building permits and septic rules in Thompson Township, Illinois

Rules another office applies inside Thompson Township

Thompson Township does not set these itself; the county, a health district or the state does, and they apply to every address inside its limits.

• Building permitRequired

  New houses, accessory buildings, decks, structural changes and electrical, plumbing or life-safety work on land inside Thompson township, administered by the county Planning & Development Department

  • Accessory structures under 120 square feet that contain no electrical or plumbing do not need a building permit, but must still meet zoning setbacks.
  • A permit fee is due after approval and no work, including excavation, may begin before payment; work started before payment can incur penalty fees.
  • A building permit is not issued until the septic permit is issued (see septic claims), and permit work must start within 6 months.
  • Applicability to Thompson township assumes no incorporated municipality; no official page checked states this for Thompson township.

  accessory structure exemption threshold: < 120 square feet (only if no electrical or plumbing)

  “a permit must be obtained prior to beginning any construction or excavation. this include: new houses, accessory buildings, decks, structural changes or repair, any work that involves electrical wiring, plumbing, and/or life safety codes.”

• Building code adoptedAdopted

  Building construction in unincorporated Jo Daviess County, including land inside Thompson township (no incorporated municipality verified there)

  • Applies to building construction under the county building permit program; the state plumbing code and the Illinois Accessibility Code are listed in the same handout.
  • The handout says the full list of adopted codes with amendments is on the county website; the amendments were not read.
  • Plumbing is also governed by the state plumbing code (2014 edition, IDPH); inspections must be done by licensed plumbers under the Illinois Plumbing License Act as quoted in the handout.

  International Building Code: 2021 edition (with appendix chapter g) · International Residential Code: 2021 edition (with appendix chapters a, b, c, d, e, g, j, m, and q)

  “the following technical codes have been adopted and made a part of the building code, effective 01/01/2025: o international building code: 2021 edition, including appendix chapter g”

• InspectionsRequired

  Permitted construction on land inside Thompson township, inspected by the county Planning & Development Department

  • Owner or contractor must call Planning & Development at (815) 591-3810 to schedule each inspection; calls are due 3-4 hours before pouring a footing and 24 hours before the rough mechanical/electric, post-insulation and final inspections.
  • Required inspections: footings, framing before siding, rough-in electrical/plumbing/mechanical before insulation, post-insulation for conditioned space, and final prior to occupancy.

  additional inspection fee: 50 USD (per inspection, only when additional inspections are required by work not ready or continuing violations)

  “inspections are required. call the planning & development department at (815) 591-3810 before the work is ready.”

• Certificate of occupancyRequired

  Buildings constructed under a county permit on land inside Thompson township

  • The county issues occupancy certificates; the final inspection is 'ready for occupancy'.
  • Projects in special flood hazard areas must provide a finished-construction elevation certificate before an occupancy permit issues.

  “do not occupy building until final occupancy certificate has been issued”

• Zoning districtsPublished

  County zoning district map covering unincorporated Jo Daviess County, including land inside Thompson township

  • The county zoning map is published in 11 x 17 and 24 x 40 versions; the map itself was not opened, so which districts apply to Thompson township parcels is not confirmed.
  • Districts named in the handout include AG, R-1 and R-2.

  “zoning map 11" x 17" zoning map(low resolution) (pdf)”

• SetbacksDistrict specific (with conditions)

  Side and rear setbacks for parcels in the agricultural (AG) district in unincorporated Jo Daviess County, including land inside Thompson township

  • The side and rear setbacks are shown in a county handout summary; the Title 8 text was not read.
  • Applies on top of frontage setbacks (see the township-road claim).

  side setback: 20 feet · rear setback: 40 feet

  “side & rear setbacks. (in ag & r-1, side setback is 20’, & rear setback is 40’)”

  2 more reviewed findings on this topic

  • District specific (with conditions) — Side and rear setbacks for parcels in the R-1 district in unincorporated Jo Daviess County, including land inside Thompson township, if the R-1 district is mapped there

    “side & rear setbacks. (in ag & r-1, side setback is 20’, & rear setback is 40’)”

  • Specified — Frontage setbacks from township roads for structures on land inside Thompson township

    “township roads: 50 ft from the property line/ 80 ft from the centerline of the roadway”

• Lot coverageDistrict specific (with conditions)

  Nonpermeable surface coverage on parcels in unincorporated Jo Daviess County, including land inside Thompson township

  • The county limits nonpermeable coverage by zoning district; the numeric limit is in the district ordinance, which was not read.
  • Non-agricultural accessory area limits in AG apply separately (handout: on lots less than five acres, less than 5,000 sq ft), not verified as a Title 8 provision.

  “jo daviess county does have limits on how much of your land can be covered in nonpermeable surface. please see the ordinance for your zoning district”

• Who permits septicCounty (with conditions)

  Private septic systems on land inside Thompson township, administered by the Jo Daviess County Health Department (Environmental Health)

  • Galena Territory and Apple Canyon Lake have extra engineered-drawing and architectural-review requirements; Thompson township is not stated to be inside them.

  “the department staff reviews plans, issues permits, and inspects the construction of new and replacement private septic systems”

• Septic permitRequired

  New or replacement septic systems on land inside Thompson township, issued by the county health department before a building permit

  • Septic systems must be installed by a licensed septic installation contractor, who applies for the permit.
  • A septic permit or sign-off must be issued before the building permit (quoted in the handout).

  “you or your septic contractor, are required to obtain a septic permit from the jo daviess county environmental health department.”

• Septic inspectionRequired

  Septic system installations on land inside Thompson township

  • Inspection checks correct location, proper sizing and compliance with state code and county ordinance; a report with a site map is kept on file.
  • Real-estate septic evaluations are not required by the health department but may be required by lenders or contracts.

  “inspection - once the septic installation contractor has completed the septic installation, an inspection takes place to check if the system was installed in the correct location, is sized properly, and meets applicable state code and county ordinance.”

• Well permitRequired

  Private water wells on land inside Thompson township

  • Wells must be installed by a licensed well driller who applies for the permit; the county inspects the installation and keeps a construction and pump installation report.
  • Geothermal closed-loop systems also need a permit and inspection (per the potable water page summary).

  “all private water wells are to be permitted, installed by a licensed well driller, and inspected to determine if the installation meets applicable state code and local ordinance.”

• Agricultural exemptionConditional

  Agricultural structures on land inside Thompson township, handled by the county Planning & Development Department

  • An agricultural exemption statement and affidavit is required for ag structures; the exemption criteria were not read in the form.
  • Ag structures carry extra submittals per the handout (agriculture option on the permit form).

  “if ag structure, ag exemption statement & affidavit.”

• Subdividing landRegulated (with conditions)

  Division of land in unincorporated Jo Daviess County, including land inside Thompson township

  • Subdivision Regulations are Title 9 of the county code; a subdivision application and checklist is on the Planning & Development forms list (revised 11-13-2024).
  • Septic system development in subdivisions is reviewed by the health department (Private Sewage Disposal page).

  “the planning and development department is responsible for administering and enforcing the county's building code, zoning ordinance, guest accommodations ordinance, subdivision regulations”

• Building in a floodplainRequired

  Construction in special flood hazard areas inside Thompson township only

  • Applies only if the parcel is in an area vulnerable to floodwaters; the flood map status of Thompson township parcels was not checked.
  • An elevation certificate based on construction drawings is required before a building permit; a finished-construction elevation certificate is required before an occupancy permit.

  “jo daviess county has a special flood hazard areas ordinance. if your project will be located in an area that is considered to be vulnerable to floodwaters, you are subject to this ordinance.”

• Short-term rentalsLimited

  Guest accommodations (short-term rental) use of a dwelling on land inside Thompson township

  • Guest accommodations need a license under the county guest accommodations ordinance (Title 4, chapter 6) and the program has different requirements than a single-family house.
  • The handout says to contact Planning & Development to review plans for compliance with the program.

  “note properties used in the guest accommodations program (short term rental) do have different requirements than for a single-family house.”

• Permit feesPublished

  Building, zoning certificate and related permit fees for land inside Thompson township

  • Fees are paid after approval and no work may start before payment.
  • Work started before a permit is issued is charged at 100% increase (penalty) per the handout.
  • The Planning & Development page links a 'fee schedule as of 12-12-2024 (pdf)' which is newer than or equal to the handout's 2025 version; the schedule was not opened, so the handout figures may be superseded.

  building permit fee: 4 USD per $1,000 of cost value (value x 0.004) · application fee (base fee): 75 USD (per the handout's building permit fee schedule) · flood area development permit: 100 USD (per the handout's building permit fee schedule)

  “$4.00 per thousand dollar cost value (value x 0.004)”

• Permit processPublished

  Building permit application review for land inside Thompson township

  • Review takes about 15-20 working days after a complete packet is received.
  • Solar permits may take longer and need interconnect sign-off; work must start within 6 months of issuance and have consistent inspections.

  plan review time: 15-20 working days (after a complete application packet)

  “building permits review time is approximately 15 - 20 working days after we have received a completed application packet.”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission; ask Thompson Township or Jo Daviess County directly.

• Owner-builder exemption — Owner-builder permit eligibility inside Thompson township
• Local zoning — Whether Thompson township itself adopts and administers a zoning ordinance
• Minimum dwelling size — Minimum dwelling size for a home inside Thompson township
• Minimum lot size — Minimum lot size for residential or agricultural parcels inside Thompson township
• Building height — Building height limits for structures inside Thompson township

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.