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

Rules another office applies inside Mission Township

Mission 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 dwellings and accessory structures in unincorporated LaSalle County, including unincorporated land inside Mission township

  • Permit is required for structures 200 square feet or larger, or with a side of 20 feet or greater; smaller structures are listed as not requiring a permit.
  • Any structure inside a corporate city or village boundary is listed as not requiring a county permit.
  • Before a building permit is issued, county subdivision, floodplain, mobile home park, setback and zoning ordinances must be met, and a copy of an approved well permit and septic permit from the county health department must be attached.
  • Construction started before a permit is issued is subject to a penalty of double the permit fee.

  “the structure is one of the following: 1. 200 s.f. or larger or; 2. has a side of 20 feet or greater”

• Building code adoptedAdopted (with conditions)

  Residential building permits in unincorporated LaSalle County, which includes unincorporated land inside Mission township

  • The brochure lists the 2024 and 2023 national electric code as amended by the LaSalle County board for one and two family dwellings; the residential code year is not stated in the excerpt.
  • Building codes apply only to structures that require a county building permit; structures inside a corporate city or village boundary are excluded from county permits.
  • Bona fide agricultural buildings are exempt from county building code provisions and fees, see agricultural-exemption claim.

  “residential structures that require building permits are subject to the international residential codes”

  One more reviewed finding on this topic

  • Adopted (with conditions) — Non-agricultural commercial, industrial, institutional and multi-family buildings that need a county building permit in unincorporated LaSalle County, including unincorporated land inside Mission township

    “are subject to the international building code, 2024; international fire code, 2024”

• InspectionsRequired

  Structures that receive a county building permit in unincorporated LaSalle County, including unincorporated land inside Mission township

  • Inspections must be scheduled by calling 847-510-4104 with 48 hours allowed for scheduling.
  • Agricultural buildings declared bona fide agricultural are exempt from county building code inspections; they remain subject to Illinois Department of Public Health plumbing inspections.

  “building code inspections will apply to all structures which receive building permits.”

• Certificate of occupancyRequired

  Occupancy and use of a new or altered structure in unincorporated LaSalle County, including unincorporated land inside Mission township

  • Occupancy permits are issued by county building code inspectors after a final inspection is passed.
  • The county health department must approve the well and septic before an occupancy permit is issued; the owner must request and certify that approval to the building inspectors.

  “occupancy and use of a structure (which includes but is not limited to moving furniture and personal items into the structure) is forbidden without an occupancy permit.”

• Zoning districtsPublished (with conditions)

  Zoning districts for unincorporated LaSalle County, including unincorporated land inside Mission township

  • The district map for Mission township itself was not opened; the ordinance refers to a zoning district map of each township of the county.
  • Districts are A-1, AC, R-1 (rural residence, labeled RR in sec. 8.1), R-2, R-3, B-1, B-2 and I-1.

  “the location and boundaries of the districts established by this ordinance are as shown on the zoning district map of each township of the county”

• Minimum lot sizeDistrict specific (with conditions)

  Single-family detached dwellings in the R-2 single family residence district of unincorporated LaSalle County, where mapped

  • The 10,000 sq ft minimum applies only where the lot is served by public sanitary sewer and water; private systems need 1 acre.
  • Minimum lot width is 75 feet with public sewer and water, and 150 feet with private systems.

  minimum zoning lot area with public sewer and water: >= 10000 sq ft (served by public sanitary sewer and water) · minimum zoning lot area with private sanitary or water systems: >= 1 acre (served by private sanitary or private water systems)

  “the zoning lot shall be not less than ten thousand (10,000) square feet in size for properties that are served by public sanitary sewer and water”

  2 more reviewed findings on this topic

  • District specific (with conditions) — Single-family detached dwellings in the A-1 agriculture district of unincorporated LaSalle County (applies inside Mission township only where A-1 is mapped and the township has no zoning of its own)

    “1. single family detached dwellings: the zoning lot shall be not less than thirty-five (35) acres.”

  • District specific (with conditions) — Single-family detached dwellings in the rural residence (RR) district of unincorporated LaSalle County, where mapped; the ordinance labels this district RR in sec. 8.1 and R-1 in sec. 6.0

    “1. single family detached dwellings: the zoning lot shall not be less than one (1) acre in size.”

• SetbacksDistrict specific (with conditions)

  Principal buildings in the A-1 agriculture district of unincorporated LaSalle County, where mapped

  • Front yard depends on road class: 70 ft from centerline of a township road, 85 ft from a county road, 100 ft from a state or federal route.
  • Front setback is at least 30 feet from the edge of the road right-of-way or roadway easement in all cases.
  • The brochure summarizes the same county setbacks (70, 85, 100 feet front; 10 feet side and rear) and states that the county setback ordinance dates to 1966.

  front setback from township road centerline: 70 ft (85 ft county road; 100 ft state or federal route) · side yard: 10 ft · rear yard: 10 ft

  “* 70 feet from a twp road, 85 feet from a county road, 100 feet from a state or federal road”

  2 more reviewed findings on this topic

  • District specific (with conditions) — Single-family detached dwellings in the rural residence (RR) district of unincorporated LaSalle County, where mapped

    “* 70 feet from a twp road, 85 feet from a county road, 100 feet from a state or federal road”

  • District specific (with conditions) — Single-family detached dwellings in the R-2 single family residence district of unincorporated LaSalle County, where mapped

    “* 70 feet from a twp road, 85 feet from a county road, 100 feet from a state or federal road”

• Building heightDistrict specific (with conditions)

  Dwellings in the A-1 agriculture district of unincorporated LaSalle County, where mapped

  • Non-dwelling buildings on lots of one acre or more have no height limit; on lots under one acre, non-dwelling buildings are capped at 36 feet (see quote).

  maximum building height, dwelling units: <= 36 feet (A-1 agriculture district)

  “and on all buildings used as dwelling units the building height shall not exceed thirty-six (36) feet in height”

  2 more reviewed findings on this topic

  • District specific (with conditions) — Single-family detached dwellings in the rural residence (RR) district of unincorporated LaSalle County, where mapped

    “single family detached dwellings shall not exceed thirty-six (36) feet in height.”

  • District specific (with conditions) — Single-family detached dwellings in the R-2 single family residence district of unincorporated LaSalle County, where mapped

    “all single family detached dwellings shall not exceed thirty-six (36) feet in height”

• Living in an RVLimited

  Living or sleeping in a recreational vehicle on private land in unincorporated LaSalle County, including unincorporated land inside Mission township

  • Not allowed in a subdivision, an unincorporated platted town, or on a parcel with an existing residence, unless otherwise permitted by the ordinance.
  • Living or sleeping use is capped at 180 days in a calendar year.

  maximum days of living or sleeping use per calendar year: <= 180 days (not in subdivisions, unincorporated platted towns, or on parcels with an existing residence)

  “a recreational vehicle, as defined in chapter 3, may be used for living or sleeping purposes for a period not exceeding 180 days in a calendar year”

• Manufactured homesLimited

  Manufactured or mobile homes on permanent foundations in the R-1 district of unincorporated LaSalle County, including unincorporated land inside Mission township

  • Listed in the R-1 district's special-use list, so a special use permit is needed; the list position was read from the ordinance text.
  • The R-2 district lists the same condition for manufactured homes on permanent foundations (see second evidence), so it is a special use there too.
  • The county's flood damage control and building permit rules also apply to installing a manufactured home on a permanent site.

  size threshold for special use: < 1000 sq ft (or older than 10 years)

  “mobile homes or manufactured homes with a permanent foundation. if less than 1000 square feet in size and/or greater than 10 years old”

• Accessory dwellingsLimited

  Accessory dwelling units (echo housing) in the residence districts of unincorporated LaSalle County, including unincorporated land inside Mission township

  • The county fee schedule describes accessory dwelling units as special uses requiring a special use permit.
  • The R-2 district lists accessory dwelling unit as a use (see second evidence); the exact permitted or special classification in each district was not confirmed.

  special use fee for accessory dwelling unit: 100 USD (special use procedure, plus notice and legal publication costs)

  “special uses for accessory dwelling unit (echo housing) is $100”

• Who permits septicCounty (with conditions)

  Private sewage disposal (septic) systems on land inside Mission township, which is served by the LaSalle County Health Department under county rules

  • The brochure refers to the Private Sewage Disposal Licensing Act and Code (a state code) and directs applicants to the county health department for it.
  • The health department's environmental health program includes private sewage disposal for the county; each licensed environmental health practitioner covers a specific area of the county, and the Mission township assignment was not confirmed.

  “these programs include food sanitation, private sewage disposal, water well program, nuisance control”

• Septic permitRequired

  New construction served by a private septic system on land inside Mission township (unincorporated LaSalle County)

  • The approved septic permit must be attached to the county building permit application.
  • The county permit instructions ask for a plat of survey and plot plan showing wells, septic tanks and sewer lines, and include a soil investigation as part of the sewage permit process (from the health department permit instructions, not opened in this session).

  “5. copy of approved septic permit from lasalle county health department”

• Off-grid sanitationLimited

  Homes on private septic and private water in unincorporated LaSalle County, including unincorporated land inside Mission township

  • Private sanitary and water systems are recognized in the R-2 and rural residence district lot rules, but require a 1-acre lot.
  • The rural residence district is meant primarily for areas where public utilities are not readily available.
  • A county septic permit and health department approval are still required (see septic-permit claim).

  “the zoning lot shall not be less than one (1) acre in size for properties served by private sanitary or private water systems”

• Well permitRequired

  New construction with a private water well on land inside Mission township (unincorporated LaSalle County)

  • The approved well permit must be attached to the county building permit application.
  • Water well construction is governed by the Water Well Construction Code named in the brochure (state code).

  “4. copy of approved well permit from lasalle county health department”

• Agricultural exemptionConditional

  Buildings used for bona fide agricultural uses in unincorporated LaSalle County, including unincorporated land inside Mission township

  • The exemption covers county building code inspections and building code fees only; the building permit and a $25 agricultural-use fee still apply.
  • Gross agricultural income of $5,000 or more to the operator is required, with proof of prior-year income and a sworn affidavit.
  • Agricultural structures remain subject to setbacks and other applicable state and federal rules.

  agricultural use permit fee: 25 USD (not a building permit fee) · minimum gross agricultural income: >= 5000 USD

  “if these structures are declared bona fide agriculture structures and will be used for agricultural purposes they are exempt from county building code inspections and building code fees”

• Subdividing landRegulated (with conditions)

  Land divisions and platted subdivisions in unincorporated LaSalle County, including unincorporated land inside Mission township

  • Lots created by division must meet the district bulk regulations; corner lots must be 25 feet wider than the minimum.
  • Divisions require land or cash donations under the county subdivision regulations.
  • Preliminary plat filing fee is $100 per lot to the county health department plus $200 plus $50 per lot (fee schedule).
  • Mission township's own subdivision ordinance and 2025-2026 moratorium were not found on an official Illinois township page; the Minnesota Mission township documents were not used.

  “subdivision ordinance fee for filing preliminary plat - lasalle county for submittal or resubmission*”

• Driveway accessRequired

  Driveway access onto county roads in unincorporated LaSalle County, including unincorporated land inside Mission township

  • The LaSalle County highway access ordinance must be met before a county building permit is issued.
  • Access onto township roads is governed by the township, which was not verified; the county highway department is the contact for county roads.

  “lasalle county highway access ordinance for more information contact the lasalle county highway department at 815-434-0743.”

• Building in a floodplainRequired

  Development in unincorporated LaSalle County, including unincorporated land inside Mission township, where the parcel is in a regulated flood area

  • The county floodplain ordinance must be met before a building permit issues; the brochure does not say which parcels are in a flood area, and the ordinance text was not opened.
  • The fee schedule charges flood damage control fees for construction valued above $100,000 and other development.

  “subdivision ordinance floodplain ordinance mobile home park ordinance setback ordinance zoning ordinance”

• Permit feesPublished (with conditions)

  Building and zoning permit fees for construction in unincorporated LaSalle County, including unincorporated land inside Mission township

  • Residential building code fees are by square foot (new construction $0.22 per sq ft, accessory $0.17 per sq ft, with minimums) plus separate electrical, plumbing and HVAC fees.
  • Fee schedule footer reads updated: december 2025 while the file name reads 2026; the schedule is treated as current as published.
  • Permits started before the permit is issued carry a late fee of double the permit fee.
  • Fees are nonrefundable; the applicant also pays certified mailing and legal publication costs for zoning hearings.

  new home residential plan review: 150 USD (plus residential building code fees) · new residential construction building code fee: 0.22 USD per sq ft (minimum $130)

  “residential plan review 1. new home $150.00 2. accessory structure $75.00”

• Permit processPublished (with conditions)

  Building permit application process in unincorporated LaSalle County, including unincorporated land inside Mission township

  • Apply at least 30 days before anticipated building; application must include two copies of construction documents, a site diagram, and approved well and septic permits.
  • Setbacks must be flagged or staked after submission; an inspector checks setbacks before and after construction.
  • Applications missing required attachments are not accepted; inspection scheduling is by phone.

  advance application time: >= 30 days

  “apply for a permit at least 30 days in advance of anticipated building.”

Still unanswered

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

• Owner-builder exemption — Owner-built construction in unincorporated LaSalle County, including unincorporated land inside Mission township
• Local zoning — Land inside Mission township, LaSalle County, Illinois: whether the township itself adopts and administers a zoning ordinance
• Minimum dwelling size — Minimum dwelling floor area in unincorporated LaSalle County, including unincorporated land inside Mission township
• Tiny homes — Tiny home occupancy on private land in unincorporated LaSalle County, including unincorporated land inside Mission township
• Short-term rentals — Short-term rental of a dwelling on private land in unincorporated LaSalle County, including unincorporated land inside Mission 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.