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Accessory Dwelling Units gain momentum as cities seek affordable housing options

ADUs are shown on residential lots in an attic, above a detached garage, as a stand alone building in the back yard, attached to a house, above and attached garage, and as a walk-out basement.
Because they can be added to a property in many ways, ADUs are a flexible housing choice.

As higher housing costs and interest rates continue to challenge aspiring homebuyers across Greater Des Moines, more communities are reevaluating zoning and land use policies and expanding affordable housing options. A recent survey by the Polk County Housing Trust Fund (PCHTF) and AARP Iowa highlights how communities are turning to accessory dwelling units as one way to help.

An accessory dwelling unit
Local nonprofit HOME Inc built this ADU in 2022

Accessory dwelling units are smaller homes that share a lot with a larger single-family home. They may be attached to the main house, located in a basement, above a garage, or built as a stand-alone building in the back yard. While ADUs are typically more common in high-priced coastal real-estate markets, higher housing prices are increasing Central Iowans’ interest in ADUs as well.

“After the Polk County Board of Supervisors approved ADUs across all residential areas in unincorporated parts of Polk County in August, we wanted to get a clearer picture of current ADU policies, so we reached out to a number of other local communities to gather basic information about their rules,” said Toby O’Berry, executive director of the Polk County Housing Trust Fund. “Eight of the 12 who responded told us they allow ADUs in some form today, with others showing future interest.”

ADUs are not the sole housing market solution, but they are an important one because they offer affordability and blend well in existing neighborhoods. Brad Anderson with AARP Iowa said a key benefit of ADUs is their flexibility for homeowners.

“The ADU might be rented to provide additional household income, or it might be a home for an adult child after college or a place for a senior family member to live independently close to family,” Anderson said. “That one structure can play multiple beneficial roles over time.”

AARP, a prominent advocate for ADUs, publishes a guide to these housing units and a model ordinance states and local governments can use to allow ADUs at

The survey aims to raise awareness about ADU policies and encourage communities to create homeowner-friendly, navigable policies. Small adjustments to local policies, such as parking requirements, design guidelines, and permitting processes can be the key difference in whether ADUs are a cost-effective option for homeowners or not.

Where ADUs are allowed, local policies for them can vary widely, and they may not be permitted in all areas of a city. It’s always best to talk with local building officials before beginning an ADU project.

The Polk County Housing Trust Fund has summarized key trends from the survey on a new fact sheet as well as a list of local government officials residents may contact to learn more about policies for their neighborhoods. PCHTF and AARP are also sharing more detailed survey response information with interested local governments.

“Allowing ADUs is just one way communities can adjust zoning policies to meet housing demands and provide residents greater affordability. We look forward to continuing to discuss options like this across Greater Des Moines,” O’Berry said.

To learn more, download the Trust Fund's new fact sheet highlighting today's policies allowing accessory dwelling units in Greater Des Moines:

Download PDF • 724KB


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