5 county-level rules, plus city-specific rules for 1 city in Polk County, Iowa.
Verified from official government sources
Unincorporated Polk County allows one ADU per property, up to 1,200 sq ft and no larger than the principal residence. The owner must live on-site, the ADU meets principal-dwelling setbacks, and none is allowed in a FEMA floodplain.
Polk County Zoning Ordinance, Art. 4, Div. 4, Sec. 2 (Accessory dwelling unit)
A maximum of one (1) accessory dwelling unit may be permitted per property. The gross square footage of the accessory dwelling unit shall not exceed one thousand two hundred (1,200) square feet of gross floor area... Accessory dwelling may not be larger than the existing principal residence.
A shed under 720 sq ft must sit at least 5 feet from side and rear property lines; larger sheds need 10 feet. Sheds must be at least 10 feet from the house, cannot exceed 24 feet in height, and generally cannot go in the front yard.
Polk County Zoning Ordinance, Art. 4, Div. 6, Sec. 1(G) (Residential Accessory Buildings)
If the gross floor area of an accessory building is: (1) Seven hundred twenty (720) square feet or less, it shall be located at least five (5) feet from the side or rear property line; (2) More than seven hundred twenty (720) square feet, it shall be located at least ten (10) feet from the side or rear property line.
Polk County's Zoning Ordinance has no separate garage-conversion rule. Converting a garage to living space is treated as an addition or an accessory dwelling unit and must meet ADU standards, district setbacks and the Polk County Construction Code.
A carport is regulated as an accessory building. It must be at least 10 feet from the house, 5 feet from side/rear lines (10 feet if over 720 sq ft), cannot exceed 24 feet in height, and generally cannot sit in front of the principal dwelling.
Polk County Zoning Ordinance, Art. 4, Div. 6, Sec. 1(C),(F) (Residential Accessory Buildings)
An accessory building, in-ground pool or above-ground pool must be located at least ten (10) feet from a principal structure... The height of an accessory building shall not exceed the height of the principal building or twenty-four (24) feet whichever is greater.
Portable tiny homes cannot be used as accessory dwelling units in unincorporated Polk County. A fixed, code-compliant tiny house on a foundation is treated as a single-family dwelling or ADU and must meet all zoning and building-code standards.
Polk County Zoning Ordinance, Art. 4, Div. 4, Sec. 2 (Accessory dwelling unit)(6)
Use of a single wide mobile home, travel trailer or recreational vehicle (RV), portable tiny home or other temporary/ portable structure as an accessory dwelling shall be not be permitted as an ADU.
1 cities in Polk County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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