Accessory Structures in Iowa (2026)
39 rules on the books across Iowa, 16 cities and counties. Select a rule to read the full details.
Severity: Few Restrictions · Light Restrictions · Some Restrictions · Significant Restrictions · Heavy Restrictions
ADU Rules
Rules for building accessory dwelling units (granny flats, in-law suites) including size limits, parking requirements, and owner-occupancy rules.
Dubuque
Significant RestrictionsDubuque allows one accessory dwelling unit per lot as a conditional use in the R-1, R-2, R-2A, R-3, R-4, OR, OC and C-1…
Read full rule →Ames
Some RestrictionsIn the City of Ames, Iowa, an Accessory Dwelling Unit is permitted on any lot with a single-family residence under Ames…
Read full rule →Cedar Rapids
Some RestrictionsAn accessory dwelling unit in Cedar Rapids must sit on the same lot as an existing single-unit home and is capped at…
Read full rule →Davenport
Some RestrictionsDavenport must allow one ADU per single-family lot under Iowa's SF 592 (2025). City zoning caps ADUs at 1,000 square…
Read full rule →Iowa City
Some RestrictionsIowa City permits one accessory dwelling unit per single-family lot under Zoning Code section 14-4C-2A. The ADU must…
Read full rule →Johnson County
Some RestrictionsJohnson County treats attached auxiliary dwelling units as an accessory use and detached units as a conditional use in…
Read full rule →Linn County
Some RestrictionsLinn County allows one accessory dwelling unit per parcel with an existing single-family home, capped at 1,200 square…
Read full rule →Polk County
Some RestrictionsUnincorporated Polk County allows one ADU per property, up to 1,200 sq ft and no larger than the principal residence…
Read full rule →Sioux City
Some RestrictionsSioux City allows two types of accessory dwelling units, but only on single-family lots of at least 7,000 square feet…
Read full rule →Story County
Some RestrictionsAn accessory dwelling unit on unincorporated land in Story County needs its own zoning permit, its own 911 address, and…
Read full rule →West Des Moines
Some RestrictionsIn the City of West Des Moines, an accessory dwelling unit, called a second dwelling unit in the zoning code, can be…
Read full rule →ADU Owner Occupancy
Whether the property owner must live on-site to operate an ADU, deed-restriction requirements, and recent state-law changes lifting owner-occupancy rules.
Johnson County
Some RestrictionsJohnson County's Unified Development Ordinance allows one auxiliary dwelling unit per property in the A, AR, SF, RS…
Read full rule →Polk County
Some RestrictionsAn accessory dwelling unit in unincorporated Polk County requires the property's legal owner to actually live there…
Read full rule →ADU Rental Restrictions
Whether an ADU can be rented short-term (Airbnb), 30-day minimums, separate rental licenses, and long-term lease requirements.
Ames
Significant RestrictionsIn the City of Ames, Iowa, an Accessory Dwelling Unit or single-family residence intended for rental use must be…
Read full rule →Polk County
Some RestrictionsPolk County's accessory dwelling unit rules stop an ADU from becoming its own separate property. The zoning ordinance…
Read full rule →Shed & Carport Rules
When a storage shed or carport needs a permit, the square-footage exemption thresholds, and the setback and height limits that apply either way.
Adair County
Some RestrictionsAdair County has no general shed, setback or building-permit rule, so this applies only inside the mapped special flood…
Read full rule →Ames
Some RestrictionsIn the City of Ames, Iowa, detached garages and accessory buildings on single-family lots are capped at 900 square feet…
Read full rule →Ankeny
Some RestrictionsDetached sheds and accessory buildings in Ankeny's one- and two-family residential zones must sit in the rear yard…
Read full rule →Black Hawk County
Some RestrictionsIn unincorporated Black Hawk County, accessory buildings and sheds must sit in the side or rear yard, stay at least…
Read full rule →Cedar Rapids
Some RestrictionsIn Cedar Rapids, a shed or detached garage can't go up before the house does, must stay out of every required yard…
Read full rule →Des Moines
Some RestrictionsA detached shed, playhouse, or pet shelter under 120 square feet needs no Des Moines building permit; anything larger…
Read full rule →Dubuque
Some RestrictionsDubuque caps every detached accessory structure, including storage sheds, at 15 feet in height and counts its footprint…
Read full rule →Iowa City
Some RestrictionsA detached shed in Iowa City can sit as close as 5 feet from a side or rear lot line, or 3 feet if it is set back 60…
Read full rule →Johnson County
Some RestrictionsJohnson County's amended building code exempts one-story detached tool sheds and playhouses up to 200 square feet from…
Read full rule →Linn County
Some RestrictionsUnincorporated Linn County caps detached sheds and other accessory structures at 25 feet tall in most residential…
Read full rule →Polk County
Some RestrictionsA shed under 720 sq ft must sit at least 5 feet from side and rear property lines; larger sheds need 10 feet. Sheds…
Read full rule →Sioux City
Some RestrictionsA Sioux City carport or porte-cochere needs a building permit and tops out at one story or 16 feet; in Neighborhood…
Read full rule →Story County
Some RestrictionsIn unincorporated Story County, a shed or other accessory building must sit in the rear yard, can't cover more than 30%…
Read full rule →Waterloo
Some RestrictionsWaterloo, Iowa exempts small detached accessory buildings from a building permit under its amendment to the adopted…
Read full rule →West Des Moines
Some RestrictionsIn the City of West Des Moines, a detached shed in a single-family district cannot exceed 1,000 square feet of combined…
Read full rule →Davenport
Few RestrictionsDavenport exempts one-story sheds up to 120 square feet of roof area from a building permit, but they must still meet…
Read full rule →Garage Conversions
Rules for converting a garage into living space, including whether you need to replace the lost parking and what building codes apply.
Ames
Significant RestrictionsIn the City of Ames, Iowa, converting a contributing garage inside a designated historic district into an Accessory…
Read full rule →Cedar Rapids
Some RestrictionsCedar Rapids lets an existing garage or other accessory structure that doesn't meet current height or setback rules be…
Read full rule →Davenport
Some RestrictionsDavenport allows converting a detached garage into an accessory dwelling unit under Chapter 17.08 if the required…
Read full rule →Sioux City
Some RestrictionsSioux City bars converting a garage into an accessory dwelling unit unless the lost parking is replaced elsewhere on…
Read full rule →Story County
Some RestrictionsConverting an existing garage or other accessory structure into living space for an accessory dwelling unit is allowed…
Read full rule →Tiny Homes
Zoning rules for tiny houses on wheels and foundations, including minimum square footage requirements and where they can be placed.
Polk County
Heavy RestrictionsUnincorporated Polk County bars any standalone tiny home from qualifying as an accessory dwelling unit. The zoning…
Read full rule →Black Hawk County
Significant RestrictionsIn unincorporated Black Hawk County, Iowa, a tiny home wider than eight feet is legally a mobile home, not a…
Read full rule →West Des Moines
Some RestrictionsWest Des Moines allows a tiny home as a long-term dwelling under City Code Section 9-5-4.E.4 only once it is occupied…
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