Resources · Iowa · County zoning
How county zoning works in Iowa, and where a data center fits in
Much of the land proposed for large data centers in Iowa sits outside city limits. There, zoning is a county decision, made under Iowa Code chapter 335 rather than the city chapter. The two chapters follow a similar pattern, but several of the details differ, and those differences matter at a hearing.
Scope. This covers the state framework for counties. Your county's zoning ordinance and comprehensive plan fill in the details, so read them alongside the code. If the site is inside a city, see our guide to city zoning changes instead.
1. Who decides
Under § 335.3, the county board of supervisors may regulate the height, number of stories and size of buildings, lot coverage, yard sizes, population density, and the location and use of buildings and land for trade, industry, residence or other purposes. That power applies to land outside the limits of any city.
2. The farm exemption
Section 335.2 exempts farmland, farm houses, farm barns, outbuildings and other structures that are primarily adapted, by reason of their nature and area, for agricultural purposes, while they are used that way. A county can't require an application or fee to establish that an exemption applies. There are limited exceptions, including for structures in a floodplain.
The exemption turns on agricultural use. A proposal to change farmland to another use, such as a data center, generally raises the question of how the county's ordinance classifies that new use. How the exemption applies to a specific parcel is a question for the county attorney.
3. What the county has to consider
Section 335.5 requires county regulations to be made in accordance with a comprehensive plan, with reasonable consideration of each district's character and its suitability for particular uses. The objectives it lists mirror the city chapter, including public health and safety, adequate light and air, reducing congestion, conserving energy, and adequate transportation, water, sewerage, schools and parks. The county list also includes preserving the availability of agricultural land.
4. The zoning commission
Section 335.8 requires the board of supervisors to appoint a zoning commission of eligible electors who live in the county. The commission recommends district boundaries and regulations. The board can't hold its public hearings or take action on those recommendations until it has received the commission's final report. The commission can later recommend amendments.
5. A public hearing, with published notice
Under § 335.6, regulations and district boundaries don't take effect until after a public hearing at which parties in interest and citizens have an opportunity to be heard. Notice is published under § 331.305, which means not less than 4 and not more than 20 days before the hearing. For a change in district boundaries, the notice identifies the township and section and, where possible, describes the boundaries in terms of streets or roads.
6. What a formal protest changes
Section 335.7 sets a higher bar for approval if a written protest is signed by owners of 20 percent or more of either:
- the area included in the proposed change, or
- the area immediately adjacent to the proposed change and within 500 feet of it.
With a valid protest, the change needs a favorable vote of at least 60 percent of all members of the board of supervisors.
7. Exceptions and variances
Section 335.10 provides for a board of adjustment, which can be authorized to grant special exceptions and hear variance requests. The board of supervisors can review a variance and send it back to the board of adjustment for further study, which delays its effective date by 30 days.
City and county, side by side
| City (ch. 414) | County (ch. 335) | |
|---|---|---|
| Decides | City council | Board of supervisors |
| Hearing notice | 4 to 20 days (§ 362.3) | 4 to 20 days (§ 331.305) |
| Protest area | 20% of the lots in the change, or of property within 200 feet | 20% of the area in the change, or of the adjacent area within 500 feet |
| Vote after a valid protest | Three-fourths of all council members | 60% of all supervisors |
| Farm exemption | Not in chapter 414 | Yes, § 335.2 |
Questions worth asking about a proposal
- Is the site outside every city's limits, so the county ordinance applies?
- How does the county ordinance define a data center, and in which districts is one allowed?
- Is the request a rezoning, a special exception, a variance or something else?
- What did the zoning commission recommend, and is its final report available?
- When was notice published, and does it fall within the 4 to 20 day window?
- What does the comprehensive plan say about this area and about agricultural land?
Not legal advice. This is a general explainer of the state framework as of September 2026, written by technical consultants, not attorneys. Code sections can be amended, and your county's ordinance governs the details. For decisions on a specific matter, consult your county attorney or other legal counsel.
Sources
- Iowa Code § 335.2, Farms exempt: https://www.legis.iowa.gov/docs/code/335.2.pdf
- Iowa Code § 335.3, Powers: https://www.legis.iowa.gov/docs/code/335.3.pdf
- Iowa Code § 335.5, Regulations and comprehensive plan — considerations and objectives — notice, adoption, distribution: https://www.legis.iowa.gov/docs/code/335.5.pdf
- Iowa Code § 335.6, Procedure — hearings — notice: https://www.legis.iowa.gov/docs/code/335.6.pdf
- Iowa Code § 335.7, Changes — protest: https://www.legis.iowa.gov/docs/code/335.7.pdf
- Iowa Code § 335.8, Commission appointed — powers and duties: https://www.legis.iowa.gov/docs/code/335.8.pdf
- Iowa Code § 335.10, Board of adjustment — review and remand: https://www.legis.iowa.gov/docs/code/335.10.pdf
- Iowa Code § 331.305 (county publication of notice): https://www.legis.iowa.gov/docs/code/331.305.pdf