Building permits, zoning and land rules in Polk County, Iowa

Unincorporated Polk County, Iowa requires a building permit before covered construction, reconstruction, alteration, conversion or structural work begins¹. A permit expires if work does not start within six months; once work starts, it is valid for one year and also becomes void if work stops for more than six consecutive months¹. Polk County Building Services reviews plans, issues permits and inspects construction in the unincorporated county, including decks, pools, houses, additions and storage facilities⁴. The county building rules apply to unincorporated land; Mitchellville issues its own building permits inside city limits^1,5. Septic permits remain with Polk County Environmental Health Services throughout the county except Des Moines². A filing fee must accompany the application, with the amount set by the Board of Supervisors¹. Iowa excludes work on your own property from contractor registration, but county building permits and inspections still apply³. In unincorporated Polk County, the Zoning Administrator must issue a certificate of occupancy after site inspection before a newly created, changed, converted, enlarged or moved structure or premises is used; recurring maintenance and required improvements under an approved subdivision plat are exempt, and a temporary certificate may last up to 6 months¹.

Polk County Building Services and Planning & Zoning Services are both divisions of Public Works, sharing one office at 5885 NE 14 Street, Des Moines, IA 50313, phone 515-286-3705, open 7:00 am to 4:30 pm^4,6. Building Services handles your construction permit and inspections; call the same number to request an inspection once your permit is issued⁴. Planning & Zoning Services, at the same address and phone, handles zoning, the subdivision ordinance, FEMA floodplain administration, the county noise ordinance and E911 addressing⁶. Septic systems are a separate division again: Polk County Environmental Health Services, also at 515-286-3705 or publicworks@polkcountyiowa.gov, issues septic permits and reviews Time of Transfer inspection reports throughout Polk County except the City of Des Moines².

Polk County zoning applies to unincorporated land, with different use and dimensional standards by district¹. West Des Moines and Mitchellville set their own zoning; septic permits remain with Polk County Environmental Health Services for parcels in Polk County outside Des Moines^2,7,8. Lot area, setbacks, coverage and height depend on district, use and development option¹. Subdivision proposals must also satisfy the applicable zoning district's minimum bulk rules¹. Residential building height tops out at 35 feet in most districts and 40 feet in the AG and AT districts under the standard single-family rules¹. Nonresidential heights differ: AG and AT allow agricultural buildings up to 135 feet but commercial buildings up to 45 feet; commercial communication towers also face airport height, setback and collapse-radius requirements¹. Ask Planning & Zoning Services for the parcel's district before designing a house, accessory building or land division⁶. Iowa's county-zoning statute generally exempts qualifying agricultural land and structures while used for farming, although floodplain regulation can still apply⁹. Iowa requires a county to allow an accessory dwelling unit on a qualifying single-family lot subject to state conditions, but Polk County does not permit a portable tiny home to serve as that ADU^1,10.

Polk County Environmental Health Services permits and inspects septic systems throughout Polk County except the City of Des Moines². Iowa's rules require a site evaluation before a septic construction permit issues, and a system cannot be installed where public sanitary sewer is available or a local ordinance requires connection¹¹. The administrative authority may consider sewer unavailable beyond 200 feet from the building; when sewer becomes available within 200 feet, connection is required under the authority's timeframe or conditions¹¹. Only a contractor with an annual professional license from Environmental Health Services can install, alter or repair a system, though anyone can pull a permit to abandon one². Polk County's own ordinance bars aerobic treatment units outright, so if your soils are marginal, ask Environmental Health Services which system the site can support². Iowa law also requires a septic inspection by a DNR-certified inspector before you can sell or transfer a home on a septic system, and that inspection is only good for two years; if the tank hasn't been pumped by a licensed cleaner within the prior three years, it must be opened and pumped at inspection¹².

Temporary camping in an RV or camper is limited in unincorporated Polk County: no more than one unit may be used at a property at a time, for no more than 21 days in a calendar year or 14 consecutive nights in one stay, and health and waste-disposal rules still apply¹. Mobile-home dwellings are permitted in unincorporated Polk County only within the Mobile Home Park zoning district, and travel trailers, campers and RVs may not serve as a dwelling inside such a park¹. The temporary-shelter allowance in unincorporated Polk County does not authorize full-time RV residence¹. Polk County also prohibits using a portable tiny home as a standalone accessory dwelling unit, but the ordinance provision does not establish a general ban on a tiny home used as the principal dwelling¹. Ask Planning & Zoning Services whether a proposed principal tiny home fits the parcel's zoning district and dimensional rules^1,6. A code-compliant ADU remains possible under Iowa law on a qualifying single-family lot; a manufactured or mobile unit used as the ADU must be placed on a permanent foundation and converted to real property¹⁰.

1. Contact Polk County Planning & Zoning Services at 515-286-3705 to identify the parcel's zoning district, allowed use, setbacks, lot coverage, height limit and any floodplain overlay^1,6.
2. Confirm that the lot and proposed layout meet the district standards; if the project divides land, confirm subdivision requirements too¹.
3. Secure a floodplain development permit before any development in a floodplain¹.
4. Apply to Building Services before starting covered construction and include the filing fee set by the Board of Supervisors¹.
5. If the site lacks public sewer, obtain the septic permit through Environmental Health Services and use a county-licensed contractor for installation, alteration or repair².
6. Call 515-286-3705 for required inspections as work progresses⁴.
7. Obtain the certificate of occupancy after the required inspections and before occupying the completed structure¹.
8. If the driveway connects to an Iowa primary highway, obtain Iowa DOT approval before work begins¹³.

If the home you're buying is on a septic system, Iowa law requires a DNR-certified inspection before a qualifying transfer, and Polk County Environmental Health Services reviews that report, so ask for it early^2,12. Only about 26.1% of Polk County's land is rated free of severe limits for a conventional drain field, and the county bans aerobic treatment units, so confirm an acceptable system before relying on a building site^2,14. About 95.4% of the land has a slope of 15% or less¹⁴. Development in a floodplain requires a county floodplain development permit before work begins, plus all other necessary permits and a certified as-built plan when complete¹. Confirm road access and utilities before closing; in a floodplain, private roads and driveways serving a principal structure must support emergency and fire access during floods¹; we could not confirm a general county driveway permit rule, so ask Public Works before designing access⁶. Iowa requires a construction permit for private water-supply wells through the local county health department; ask Polk County Environmental Health Services about the application^2,15. The effective property-tax rate is about 1.8%, the median annual bill is about $4,364, and farmland value is about $9,677 per acre¹⁴.