Building permits, zoning and land rules in LaSalle County, Illinois

Yes. Unincorporated LaSalle County requires a written building permit before a new building or structure is erected and a construction permit before rebuilding, structural alteration, an addition, relocation or a significant change of use². For residential work covered by the ordinance’s exemptions, routine maintenance or repair, utility-service connections, structures no larger than 200 square feet with every side under 20 feet, and mobile homes placed on pads in licensed mobile-home parks are exempt, but those exemptions do not cover additions, structural alterations or significant changes of use involving a single-family dwelling, habitable residential space or accessory structure². The county applies the 2024 International Residential Code to covered non-agricultural homes and accessory structures and the 2023 National Electrical Code to covered construction². Qualifying agricultural structures and necessary farm residences have a narrower exemption discussed below, not a blanket owner-builder exemption¹. Municipal building permits come from Ottawa⁹, Mendota¹⁰, Marseilles¹¹, Earlville¹², Village of Grand Ridge¹³. Private septic permits remain with the LaSalle County Health Department in unincorporated areas⁴.

The LaSalle County Land Use Department administers building permits and the county's zoning, subdivision, floodplain, mobile-home and vacant-property ordinances in unincorporated LaSalle County^2,3. Reach the department at 815-434-8666 (fax 815-433-9303) or landuse@lasallecounty.org, at 119 West Madison Street, Room 107, Ottawa, IL 61350³. A building-permit application must include the county permit and zoning application, a dimensioned site drawing, a property description and any applicable water-supply and sewage-disposal information; a separate Health Department permit must be issued first when a water or sewage system will be installed². The county gives written approval or denial within 30 days after submittal, and a denied applicant has 45 business days to correct deficiencies and resubmit without another fee². Building-permit charges otherwise vary by project and plan review¹. SAFEbuilt schedules remote-video inspections at 847-510-4104 or ilinspections@safebuilt.com³.

LaSalle County zoning applies in unincorporated areas³. Municipal zoning is administered by Ottawa¹⁴, Streator¹⁵, Peru¹⁶, Mendota¹⁰, Marseilles¹⁷, Oglesby¹⁸, Village of Seneca¹⁹, Earlville²⁰, Village of North Utica²¹, Village of Leland²², Village of Grand Ridge²³. Private septic permits remain with the LaSalle County Health Department in unincorporated areas⁴. The online ordinance and maps are references, but the print ordinance and later County Board amendments control if they differ²⁴. Minimum lot area depends on district and utilities: an A-1 detached home generally needs 35 acres, an RR detached home generally needs 1 acre, and an R-2 detached home needs 10,000 square feet with public sewer and water but 1 acre with a private sanitary or water system; exceptions and planned-unit provisions can change the result⁵. Setbacks also vary: most districts use 70 feet from a township-road centerline, 85 feet from a county-road centerline and 100 feet from a state-road centerline; an R-2 detached home has 10-foot side and rear yards²⁵. Building-height limits are district-specific; in R-3, detached and two-family homes, mobile-home parks and certain attached homes may not exceed 36 feet⁵. In R-2, a mobile or manufactured doublewide on a permanent foundation is a permitted use when it has at least 1,000 square feet and is under 10 years old; a home below 1,000 square feet or more than 10 years old requires special-use approval after a public hearing⁵. The R-2 manufactured-home rule does not establish a minimum floor area for conventional homes or other districts; ask Land Use to classify a proposed tiny home and clarify the treatment of a manufactured home exactly 10 years old⁵.

The LaSalle County Health Department's Environmental Health program administers private sewage disposal systems in unincorporated LaSalle County⁴. Installation or repair of an individual private sewage system requires a permit; before the construction permit is issued, submit the completed application and $230 fee and allow department personnel to conduct an onsite survey⁶. Notify the Health Department for the final inspection before backfilling, and protect the designated disposal area from traffic, compaction and changes in soil during construction⁷. State rules also require plan approval before work begins and at least 48 hours' notice before construction²⁶. Only about 3.2% of LaSalle County soils are rated free of severe limitations for a conventional drain field, so establish septic feasibility early²⁷. Reach the Health Department at 815-433-3366, 717 E Etna Road, Ottawa, IL 61350, or email environmentalhealth@lasallecountyil.gov^28,29. Inside Ottawa, a private sewage system needs the city plumbing inspector’s permit³⁰. Marseilles requires a written private sewage permit signed by the Commissioner of Public Property, and LaSalle requires its authorized agent’s written private wastewater permit where public sewer is unavailable^31,32. The LaSalle County Health Department handles private septic permits in the LaSalle County portion of Streator, North Utica and Leland^4,7,33.

In unincorporated LaSalle County, an RV may be used for living or sleeping for no more than 180 days in a calendar year⁵. RV living or sleeping is not allowed for any period when the vehicle is in a subdivision, an unincorporated platted town or on a parcel with an existing residence, unless another part of the ordinance permits it⁵. We could not confirm a general temporary-camping rule or a separate tiny-home occupancy category for unincorporated LaSalle County; ask Land Use how the proposed use and design would be classified.

1. Confirm the parcel's zoning district, minimum lot area, setbacks and height limit with Land Use before design^5,25.
2. Establish the water supply and sewage plan; when either system will be installed, obtain the separate Health Department permit before the county building permit can issue².
3. Prepare the county permit and zoning application, a dimensioned site drawing, a property description and the applicable water and sewage information².
4. Apply before erecting a new structure or before rebuilding, structurally altering, adding to, relocating or significantly changing the use of one².
5. If claiming the agricultural-use exemption, submit the notarized operator affidavit, prior-year proof of at least $5,000 in gross agricultural income and the $25 compliance-permit fee; the exemption covers Building Code provisions and related code fees, not the compliance application¹.
6. Post the issued permit in plain view, begin within 9 months and finish within 2 years².
7. Obtain any floodplain or state-highway driveway approval, arrange septic inspection before backfilling and complete the building inspection before occupancy^1,7,8,34.

A new, modified or sealed water well needs a permit from Illinois or an approved local health department before work begins³⁵. All construction in an unincorporated LaSalle County floodplain requires a county permit⁸. A driveway onto a state-maintained road needs an IDOT permit before work starts³⁴. Before a land split, ask Land Use whether each proposed lot complies with the zoning district and subdivision rules²⁵. We could not confirm the county-road driveway requirement or mandatory public-water and sewer connection rules; ask Land Use about road-jurisdiction approval and Environmental Health about the proposed water and sewage arrangements.