Subdividing Land in Story County, Iowa

The baseline: Story County's Land Development Regulations

Story County has combined zoning and subdivision requirements into one code, the Land Development Regulations, administered by the Planning & Development Department. A conceptual-review meeting -- an informal session with county departments to review preliminary plans, held virtually most Thursdays -- is required before most development applications, giving a prospective subdivider an early read on staff concerns before a formal application and its associated review fees are triggered. The seven-member Planning and Zoning Commission, whose members all reside in unincorporated Story County, reviews development cases monthly, with site-plan approval, zoning-permit issuance, and on-site inspections handled by Planning & Development staff.

Within the Agricultural District (A-1), the standard minimum lot size for a dwelling is 35 net acres -- consistent with a common Iowa approach to discouraging fragmentation of productive farmland. A separate Agricultural Residential (A-R) district sets a flat 1-net-acre minimum for a dwelling. Where Story County departs from a purely binary rule is the exception built into the A-1 district itself.

The LESA exception: a soil-quality test that can shrink the 35-acre minimum to 1 acre

Story County uses a Land Evaluation Site Assessment (LESA) score to determine whether a specific A-1-zoned tract can qualify for a reduced 1-net-acre minimum lot size for a dwelling, rather than the standard 35 acres -- specifically where the LESA process identifies the land as low-to-moderate-value agricultural ground rather than prime farmland. This means the answer to "how small can I split off a home site here?" is not fixed by the zoning map alone; it depends on a parcel-specific soil-and-site evaluation. For anyone planning to carve a smaller home site out of a larger agricultural holding, this is the single most consequential local mechanism to understand, since it can be the difference between needing a 35-acre remainder parcel and needing only a fraction of that.

Practically, that means before assuming either the 35-acre standard or the 1-acre exception applies to your situation, you need Story County Planning & Development to run (or confirm) the LESA score for the specific tract in question. Because the score is evaluation-based rather than a simple lookup, build time into your planning timeline for this step, and don't assume a neighboring parcel's LESA outcome (or lack of exception) predicts your own tract's result -- soil quality varies at a fairly granular level even within the same section.

Near Ames or Gilbert: the joint Ames Urban Fringe Plan adds another layer

Iowa law allows a city to establish, by its own ordinance, extraterritorial review authority over land divisions within two miles of its boundary. In Story County, that authority is formalized as a genuine joint-governance arrangement rather than a one-sided city veto: the Ames Urban Fringe Plan is a cooperative planning effort among the City of Ames, the City of Gilbert, and Story County, with the current cooperative agreement dating to 2011 and a public draft update circulated in 2022. Within the mapped Fringe Plan area, land divisions require review by the applicable city in addition to the county, and the plan can impose urban-scale infrastructure standards -- for streets, wastewater treatment, and potable-water distribution sufficient to support emergency services -- on subdivisions that fall inside that zone.

The plan also addresses a subtler issue: because annexation by Ames or Gilbert would otherwise mechanically push the two-mile extraterritorial review boundary further outward every time either city grows, the cooperating parties agreed the cities would waive extraterritorial review jurisdiction in any area extended beyond the originally mapped Fringe Plan boundary by a later annexation. For a subdivider, this means the actual governing boundary is the Fringe Plan's mapped planning area -- not simply "whatever is within two miles of the city limits today" -- so confirming your parcel's status against the current Fringe Plan map, rather than eyeballing a distance on a general map, is essential.

What to verify before subdividing land in Story County

• Whether the parcel falls within the mapped Ames Urban Fringe Plan area, and if so, which city (Ames or Gilbert) holds extraterritorial review authority alongside the county -- confirm against the current Fringe Plan map, not just distance from the city limits.
• The parcel's LESA eligibility for a reduced agricultural minimum lot size, obtained or confirmed through Story County Planning & Development -- do not assume a 35-acre or 1-acre standard applies without this step.
• Whether a required conceptual-review meeting has been scheduled with county departments before submitting a formal subdivision application.
• If the parcel is within the Fringe Plan area, what urban-scale infrastructure standards (streets, wastewater, water distribution) would apply to a proposed subdivision.
• Current Land Development Regulations text and any recent amendments directly with Planning & Development, since zoning and subdivision codes are periodically updated.