Building permits, zoning and septic rules in Rock Island County, Illinois

Unincorporated Rock Island County, Illinois requires a building permit before constructing, enlarging, altering, repairing, moving, or demolishing a structure, changing its occupancy, or doing regulated electrical, gas, mechanical, or plumbing work¹. The county moved to the 2021 I-codes and 2020 NEC effective October 1, 2026¹¹,. A short list of small projects outside the floodplain is exempt, including a one-story accessory building no larger than 120 square feet¹². Floodplain improvements have no permit exemptions¹. Starting covered work before permit issuance doubles the fee, with no exceptions¹³. Qualified agricultural buildings receive a free permit, but still need that permit and remain subject to applicable zoning, floodplain, sewage, fire, and other rules¹⁴.

The Rock Island County Zoning & Building Safety Department handles building permits and inspections for unincorporated property at 1504 Third Avenue, Room 305, Rock Island, IL 61201; call 309-558-3771¹². Inside Moline, apply to the city for building permits¹⁵. Carbon Cliff contracts with East Moline for building permitting and inspections; private sewage still requires village and County Health Department approval^4,16. County applications go by mail, email or in person, naming the property owner and generally including detailed plans; residential review typically takes 3–5 business days¹. County building fees vary with project value, and plumbing and gas inspections cost $12 per opening¹². The registered contractor or subcontractor requests inspections, and final approval requires completed subcontracted work and smoke and carbon monoxide detectors¹².

Rock Island County administers zoning only on unincorporated land². Moline, East Moline, Silvis and Carbon Cliff have municipal zoning; private sewage remains under the County Health Department, with Carbon Cliff also requiring village sign-off^{4,17,18,19,20,21}. The county publishes district summaries, its zoning resolution and a map; identify the parcel’s district before evaluating a use^22,23. County minimum building-site sizes vary by location, from examples of 20,000 square feet to 40 acres; AG-1 requires 40 acres and AG-2 requires 15 acres^7,22. In SE-2, primary structures need 40-foot front and rear yards and side yards at least 15 feet wide totaling 30 feet⁶. Short-term rentals require a special-use permit in R-2, R-3 and U-1 but are allowed by right in R-4²⁴.

The Rock Island County Health Department requires a permit to install or repair a private sewage disposal system, including work associated with new construction, renovation, tank-only projects, and tank demolition³. Properties without municipal sewer service must dispose of wastewater under Illinois sewage codes; the Health Department offers consultations and inspections for new and existing systems²¹. Ask the Health Department what site evaluation, inspections, and fees apply before finalizing a house plan²⁵. Only about 40.6% of county soils lack a severe limitation for a conventional drain field, so soil suitability can materially affect the design and budget²⁶. A new, modified, or abandoned well also requires advance approval from the state or an approved local health department²⁷.

Unincorporated Rock Island County prohibits RV living, sleeping or housekeeping on residential lots except free stays by guests of the principal resident⁸. The county page limits those stays to 30 days per calendar year, while the ordinance says 30 consecutive days; ask Zoning & Building Safety which limit applies before planning a stay^2,8,9. Extended bump-outs and connected utilities count as occupancy, and seasonal camping along a body of water requires a Special Use Permit⁹. In R-1, a tiny home must qualify as a one-family detached dwelling on a permanent masonry or concrete foundation¹⁰. The county separately states a dwelling minimum of 900 square feet; the one-family definition also includes a 900-square-foot separation requirement, which is not a floor-area allowance^8,28. All dwellings, including manufactured homes, need a full perimeter foundation below the 42-inch frost line and an occupancy permit before habitation^1,9.

1. Ask Zoning & Building Safety to identify the parcel's district, lot size, setbacks, and floodplain status^7,23.
2. If a subdivision lies within 1.5 miles of an incorporated municipality with a subdivision ordinance, account for municipal review before county approval²⁹.
3. Obtain the Health Department permit for private sewage installation or repair and approval for well and septic plans when municipal service is unavailable^3,21.
4. Submit the building application and detailed plans by mail, email, or in person¹.
5. Pay the department-calculated fee, post the issued permit card, and have the registered contractor or subcontractor request required inspections^12,13.
6. Start within 30 days; the permit remains valid for 180 days, with one possible additional 180-day extension by written request¹².
7. Pass the final inspection and obtain the occupancy permit before moving in^1,12.

Confirm jurisdiction first: county zoning applies only outside cities and villages, and incorporated places use their own departments². Verify the zoning district and lot dimensions because minimum lot size and setbacks are district-specific^6,7. Order a soil evaluation before buying; only about 40.6% of county soils lack a severe limitation for a conventional drain field²⁶. Check road ownership too: a new entrance onto a county highway requires a free county permit, while work in a state-road right-of-way requires an Illinois Department of Transportation permit^5,30. Floodplain improvements have no county permit exemption, and floodplain occupancy requires an elevation certificate before the occupancy certificate¹. The effective property tax rate is about 2.3%, with a median annual bill near $3,372²⁶.