Zoning in Johnson County, Iowa

How the Unified Development Ordinance is structured

Most Iowa counties run county zoning as one ordinance and keep subdivision regulations, floodplain rules, and building code as separate documents, sometimes administered by different offices. Johnson County took a different approach in 2019, consolidating zoning, subdivision regulations, Sensitive Areas (environmental) regulations, floodplain management, commercial wind energy facility rules, building code, rental housing code, code enforcement, and airport zoning into a single Unified Development Ordinance (UDO) -- roughly 300 pages -- administered by one department, Planning, Development and Sustainability (PDS). Unincorporated land is organized into 27 individual zoning districts, grouped into agricultural, residential, commercial, industrial, preservation, and specialized/public/institutional categories, which PDS in turn groups into 3 general land-use areas under the county's Comprehensive Plan: agricultural/rural areas, preservation areas, and growth areas (residential, commercial, and industrial growth). The Board of Supervisors adopted the UDO on December 19, 2019, it took effect January 15, 2020, and it was recodified January 30, 2025 to incorporate amendments passed in the years since -- amendments have continued at a regular pace, including a 2024 change adding cryptocurrency production as an allowed use and adjustments to Auxiliary Dwelling Unit (ADU) acreage requirements. Because the UDO is a living document under periodic amendment, don't rely on an older downloaded copy; confirm you have the current recodified text from PDS directly.

For a specific parcel, the first practical question is which of the 27 districts applies and which general land-use area it sits in -- a growth-area district near Iowa City, Coralville, or North Liberty carries very different development expectations than a district in a preservation or agricultural/rural area. PDS's GIS Property Information Viewer and the department's own staff are the two ways to get a current, parcel-specific answer; a real estate listing's zoning description or an older printed county zoning map are not reliable substitutes given how often this ordinance has been amended.

The 2019 change that matters most for smaller parcels: a tighter agricultural exemption

Iowa Code Chapter 335 gives county zoning broad statewide exemptions for land and buildings "primarily adapted, by reason of nature and area, for use for agricultural purposes, while so used" -- in most Iowa counties, a working farm of almost any size can build a house, barn, or grain bin without a zoning permit, no questions asked. Johnson County's 2019 UDO changed how that exemption is administered locally: parcels of 40 acres or more are presumed to qualify, but for anything under 40 acres, the applicant must submit an application to the Zoning Administrator and demonstrate a combination of agricultural history or education, a genuine intent to continue significant, ongoing agricultural operations on the property, and evidence the operation is economically viable, before a new or replacement dwelling, or a new agricultural outbuilding, can proceed as an exempt use. The UDO also added separate regulation of animal-feeding operations, including per-acre animal-unit limits tied to outbuilding use.

This provision was genuinely contested, not a quiet technical change. Over the second half of 2019, the Johnson County Farm Bureau organized opposition, and dozens of farmers spoke at Board of Supervisors hearings arguing that requiring county approval before building a house, grain bin, or outbuilding -- or growing a livestock operation -- oversteps what farmers should have to justify to a county government. The ordinance nonetheless passed all three required readings on 3-2 votes in December 2019. For a buyer, the practical takeaway is specific: if you're purchasing a parcel under 40 acres in unincorporated Johnson County with any plan to farm it, keep livestock, or build an agricultural structure, treat the agricultural-exemption application as a real step in your process -- not a formality -- and get the current application requirements and Zoning Administrator's current interpretation directly from PDS before you buy or before you build.

What to confirm before buying or building on a specific parcel

• Which of the 27 zoning districts and which general land-use area (agricultural/rural, preservation, or growth) applies to the specific parcel, confirmed directly with PDS or via the county's GIS Property Information Viewer -- not from an older map or a listing description.
• If the parcel is under 40 acres and you plan any agricultural use, dwelling, or outbuilding: whether an agricultural-exemption application is required, and its current documentation standard for history, education, intent, and economic viability.
• Whether the parcel or your planned use is affected by any UDO amendment adopted since your last check of the ordinance, given the pace of recent changes (ADU acreage rules, allowed-use additions, subdivision-regulation updates).
• Whether the parcel also falls within a Sensitive Areas category (woodlands, slopes, wetlands, or a stream corridor) or a floodplain, both of which layer additional review on top of the base zoning district -- see this county's dedicated wetlands and flood-zones pages.
• Whether the parcel sits within any city's fringe-area agreement (Iowa City, Solon, and the Cedar Rapids/Swisher joint agreement are current; Coralville's expired in 2019 and Tiffin's in 2006, both without a confirmed replacement) -- see this county's dedicated subdividing-land page.