ADU Guide · Verified 2026
Building an ADU in Iowa
Iowa requires both cities and counties, not just cities, to allow at least one ADU per single-family lot, making it one of the few state laws in this research to reach unincorporated county land directly. Iowa does not override HOA restrictions, though, a real limit most homeowners in a covenant-restricted community should know about.
Quick Facts
Statewide floors set by SF 592, effective July 1, 2025. Your city may be more generous but cannot go below them.
The Three Types of ADU
A law that reaches county land directly, a real distinction
SF 592's own text specifically requires counties, not just cities, to allow at least one ADU, a genuinely broader reach than several other states' laws in this research that only bind municipalities and leave unincorporated county land untouched.
A real limit: HOAs are not preempted
Unlike Colorado, Arkansas, or Utah, Iowa's law does not void HOA covenants. The statute explicitly preserves a common interest community's authority to prohibit or limit an ADU, meaning a homeowner in a covenant-restricted subdivision can still be blocked by their own HOA even though the city or county would otherwise allow it.
A size direction worth double-checking
Iowa uses the larger of 1,000 square feet or 50% of the primary home's floor area, the opposite direction from Arkansas's rule of using the smaller of two similar figures, a real, easy-to-invert detail between neighboring states' laws.
What people get wrong
The most common mistake is assuming Iowa's statewide mandate overrides an HOA the way Colorado's does. It genuinely does not, Iowa's law leaves HOA authority over ADUs fully intact.
From Idea to Move-In: The Timeline
Who Administers It
Building It Yourself? Here's What You'll Need
Planning an ADU? Tools homeowners use in the design and layout phase:
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Check Your Local Rules
Your city may allow more than the state floor
State law sets the minimum; many Iowa cities and counties are more generous. Browse the full directory of 99 counties and every city in Iowa for local rules, fees, and building department contact details.
Browse the full Iowa directory →Not sure if your project needs a building permit, a zoning approval, or both? See our guide to building permits vs. zoning approval.
Official Sources
ADU law changes frequently and local ordinances add detail. This guide is general information, not legal advice, always confirm with your local building department. Reviewed by the StateDataIndex Editorial Team · Updated September 2026.