Garage conversion rules in Johnson County, IA — sometimes called garage-to-ADU or accessory living unit conversions — govern permits, ceiling height, egress, and parking replacement.
Converting a garage into living space in Johnson County is a change of occupancy that needs a building permit. Inspectors check egress, insulation, and smoke and carbon-monoxide alarms.
Turning a garage into a bedroom or family room changes non-habitable space into habitable space, so Johnson County and its cities permit it under the 2024 International Residential Code and the energy code. Inspectors review egress windows, ceiling height, insulation for Iowa's cold climate zone, and smoke and carbon-monoxide alarms; new wiring, plumbing, or heating draws its own permit. A finished garage conversion may also qualify as an accessory dwelling unit under Iowa's 2025 ADU law if it meets the size cap. If the garage is the way into a storm shelter, keep that access open.
Converting a garage without a permit is illegal construction subject to a stop-work order. The county can require the space brought to code or restored to a garage.
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See how Johnson County's garage conversions rules stack up against other locations.
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