Accessory Structures in Story County, IA (2026)
3 rules for unincorporated Story County, Iowa.
Verified from official government sources
ADU Rules
An accessory dwelling unit on unincorporated land in Story County needs its own zoning permit, its own 911 address, and its own approved septic permit before that zoning permit will issue. Section 86.04(3)(L) caps a converted or new ADU at 1,200 square feet, limits a parcel to one ADU, and requires it sit within 200 feet of the existing single-family home.
Accessory Dwelling Unit Rules in Story County
Some RestrictionsStory County Code of Ordinances § 86.04(3)(L)
L. An accessory dwelling unit conforming to the requirements specified herein: (1) Zoning Permit Required. A zoning permit shall be submitted for any accessory dwelling unit, including when an existing single-family dwelling or accessory structure is modified to create an accessory dwelling unit therein. (2) Wastewater and Water facilities. The accessory dwelling unit shall be provided with...
Shed & Carport Rules
In unincorporated Story County, a shed or other accessory building must sit in the rear yard, can't cover more than 30% of that rear yard, and can't be built before the main house, per Code of Ordinances § 91.01(4). Sheds under 100 square feet with no permanent foundation skip the zoning permit but still owe rear and side setbacks.
Shed and Accessory Building Rules
Some RestrictionsStory County Code of Ordinances § 91.01(4), (14)
4. No accessory building shall be erected in any required yard other than a rear yard, as provided hereinafter. ... ... B. An accessory structure that is not a part of the main building shall not occupy more than 30 percent of the rear yard. No accessory structure shall be constructed upon a lot until the construction of the main building has actually commenced, and no accessory structure shall...
Garage Conversions
Converting an existing garage or other accessory structure into living space for an accessory dwelling unit is allowed in unincorporated Story County only if the structure already meets the accessory-structure bulk standards in Table 86-2, and Section 86.04(3)(L)(5) requires every overhead or garage door on the converted portion to come out and be replaced with a matching facade.
Garage Conversion Rules in Story County
Some RestrictionsStory County Code of Ordinances § 86.04(3)(L)(5)
(5) Conversion of Existing Accessory Structures. a. Existing accessory structures conforming to the bulk requirements for accessory structures in Table 86-2 , or that are legal nonconforming structures, shall be permitted to be converted to an accessory dwelling unit. Additions to a converted accessory structure shall meet the bulk requirements for a single-family dwelling in Table 86-2 . b...
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