How Des Moines Handles Accessory Structures: A Practical Guide

Des Moines maintains 170 local ordinances across all categories, and 9 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where Des Moines falls on the strict-to-permissive spectrum compared to other cities.

Carport Rules

Des Moines zoning permits carports as accessory structures in residential districts. Building permit required. Setback, height, and coverage rules apply per Chapter 135 accessory structure tables.

Key details: Permitted in: Residential N-districts. Side/rear setback: 5 feet minimum. Max height: 15 feet. Permit required: Yes, building permit. Coverage cap: 35% of rear yard.

Construction without a permit or in violation of setbacks is a municipal infraction. Fines start at $100 and escalate; the city can require removal or relocation. Repeated violations may trigger civil penalties.

Tiny Homes

Des Moines does not allow detached tiny houses below 1,100 sq ft as a primary dwelling under Chapter 134 (Zoning Ordinance), but it does permit Accessory Household Units (AHUs) up to 1,000 sq ft or 50% of the primary house floor area on lots zoned N, NX, A, DXR, RX1, or RX2 (Ordinance 15,816, eff. Dec. 16, 2019).

Key details: Zoning Ordinance: Chapter 134 (Ord. 15,816). Effective Date: December 16, 2019. Max AHU Size: 1,000 sq ft or 50% of primary. Allowed Zones: N, NX, A, DXR, RX1, RX2. Detached AHU Setback: 5 ft from any lot line.

Erecting a tiny house as a primary dwelling that fails Chapter 134 minimum dwelling-size standards or installing an AHU without a building permit is a zoning violation. The Permit and Development Center can issue stop-work orders, deny certificates of occupancy, and require removal or after-the-fact permitting; civil penalties are pursued through the Des Moines Municipal Court.

ADU Owner Occupancy

Des Moines Chapter 134 has historically required the property owner to reside on-site (in either the primary dwelling or the ADU) as a condition of ADU permit issuance. Verification is by recorded affidavit. Iowa has no statewide preemption of owner-occupancy mandates. HOA covenants may impose additional restrictions enforced under Iowa Code Chapter 499B (condominium) and common-law restrictive covenants.

Key details: Owner-Occupancy: Required (one of two units). Affidavit: Recorded with Polk County. State Preemption: None (Iowa). Condo Law: Iowa Code Ch. 499B.

Failure to maintain owner-occupancy may trigger revocation of the ADU permit and require ceasing rental of one unit. Continuing rental in violation may be enforced under Chapter 60 municipal infractions with fines up to $750 per day. False statements on the owner-occupancy affidavit can constitute Iowa Code 720.2 (false certificate) violations. HOA/condo violations follow declaration-based fines, typically $100-$500 per occurrence, with lien rights under Iowa Code 499B.18.

ADU Impact Fees

Iowa does not authorize municipal impact fees by general statute, so Des Moines does not assess traditional development impact fees on ADUs. Standard building, electrical, plumbing, and mechanical permit fees apply under the schedule adopted by City Council. Des Moines Water Works and the Wastewater Reclamation Authority charge connection fees only if new utility service is required for the ADU.

Key details: Impact Fees: None (Iowa no general authority). State Law: Iowa Code 384.84 (utility only). Building Permit: ~$5/$1,000 valuation. Water/Sewer Connect: Only if new service.

Failure to pay required permit fees blocks issuance and inspection scheduling. Continuing work without permits triggers Chapter 60 municipal infractions up to $750 per day. Unpaid fees and infraction judgments may be filed as liens under Iowa Code 364.12A. Disputes over fee assessments may be appealed administratively or in Polk County District Court.

Des Moines is more permissive than most cities when it comes to adu impact fees. That said, there are still limits.

ADU Rental Restrictions

Des Moines requires a Rental Housing Permit under Chapter 60 (Housing) for any residential rental, including ADUs rented long-term. Short-term rentals (under 31 days) are regulated as 'transient occupancy lodging' under Chapter 134 with additional zoning approval and Hotel-Motel Tax remittance. Iowa Code 562A (Uniform Residential Landlord and Tenant Act) governs long-term tenancies. Iowa Code 364.3(11) preempts local rent control.

Key details: Rental Permit: Required (Ch. 60). STR Threshold: Under 31 days = transient. Hotel-Motel Tax: 7% city + 6% Iowa sales. Long-Term Law: Iowa Code Ch. 562A. Rent Control: Preempted (Iowa 364.3(11)).

Operating a rental without a Chapter 60 Rental Housing Permit triggers municipal infractions up to $750 per day plus possible ordered vacatur and tenant displacement protections. Failed inspections may suspend the permit. Unremitted Hotel-Motel Tax accrues with collection actions, including Polk County District Court judgments and liens. Iowa Code 562A violations create civil remedies for tenants. HOA STR violations follow declaration-based fines.

ADU Permits

Des Moines permits Accessory Dwelling Units (ADUs) under the Zoning Ordinance (Municipal Code Chapter 134, PlanDSM-aligned). ADUs are allowed in most residential zones (N1, N2, N3 neighborhood districts) as part of the 2019 zoning code overhaul. One ADU per single-family lot is permitted. Building, electrical, plumbing, and mechanical permits route through the Des Moines Development Services Department. Iowa has no statewide ADU preemption; Title IX of the Iowa Code leaves zoning to home-rule municipalities.

Key details: Code Authority: Municipal Code Ch. 134. By-Right Zones: N1, N2, N3, N4. Max Size: 800 sq ft or 75% primary. Units Per Lot: One. State Preemption: None (Iowa home rule).

Unpermitted ADU construction violates Chapter 134 with civil penalties up to $750 per day per violation under Chapter 60 (Municipal Infractions). Development Services may issue stop-work orders and demolition orders for unsafe structures. The City may seek injunctive relief in Polk County District Court. Liens may attach to the property for unpaid fines and corrective work. Iowa Code 364.22 governs municipal infraction enforcement.

Shed Rules

Des Moines requires permits for most accessory structures. Sheds must comply with zoning setbacks, height limits, and lot coverage maximums. Small structures under a certain size may be exempt from permit requirements.

Key details: Permit Exempt: Small sheds under ~200 sq ft. Location: Rear or side yard only. Setbacks: 3–5 ft from property lines. Coverage: Max % of rear yard. Easements: Cannot encroach.

Building without a permit when required: municipal infraction. Setback violations require relocation or removal of the structure.

Garage Conversions

Garage conversions to living space in Des Moines require building permits and must meet residential building code standards. Off-street parking requirements must still be satisfied after conversion.

Key details: Permit: Required. Parking: Must retain required spaces. Code: Full residential standards. ADU: May apply if separate unit. Occupancy Cert: May be required.

Unpermitted conversion: municipal infraction. May be required to restore to garage or obtain retroactive permits. Occupancy without certificate is a violation.

ADU Rules

Des Moines expanded ADU allowances in 2022 and Iowa SF 592 further requires cities to permit ADUs. ADUs up to 1,000 sq ft or half the primary dwelling size are allowed. The city offers a 10-year tax abatement on ADU value.

Key details: Max Size: 1,000 sq ft or 50% of primary. Number: One per lot. Location: Detached must be in rear yard. Tax Abatement: 10-year on ADU value. Owner Occupancy: Required in one unit.

Building without a permit: municipal infraction. Non-compliant ADUs may be required to be brought to code or removed. Occupancy violations possible.

The Bottom Line

Des Moines's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Des Moines is broadly strict or permissive.

This guide is based on Des Moines's current municipal code. Local rules can and do change, so check the individual ordinance pages for the latest details, penalties, and FAQs.