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All about Accessory Dwelling Units

An accessory dwelling unit (ADU) is a smaller home that shares the same residential lot with a larger home. Communities are allowing ADUs as a gentle way of adding new housing options with existing neighborhoods.

A drawing of six houses shows different places an adu can be added - as an attic, above a detached rear garage, as a stand-alone building in the back yard, as an addition to the house, above an attached garage, or as a basement (in this case, a walk-out basement).

In an attic

Above a detached garage

In the
back yard

As an addition

Above an

attached garage

In a basement

You can add an accessory dwelling unit to an existing home in many different ways, making them a uniquely flexible housing option.

An image thumbnail of our ADU handout.

Download our new
ADU fact sheet

The Trust Fund has produced a new fact sheet highlighting the current state of accessory dwelling unit policy in Greater Des Moines.

Watch Two Houses, One Home to see an ADU being built from start to finish

We joined local non-profit HOME, Inc. to follow their construction of an accessory dwelling unit in the Oak Park neighborhood from start to finish. Each episode features an update from the project site as well as an interview with a local housing expert.


Two Houses, One Home is hosted by Kourtney Kirkpatrick of HOME, Inc.

Two Houses, One Home
Designing an Accessory Dwelling Unit (ADU) in Des Moines, Iowa

Designing an Accessory Dwelling Unit (ADU) in Des Moines, Iowa

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We're Building an Accessory Dwelling Unit (ADU) in Des Moines, Iowa!

We're Building an Accessory Dwelling Unit (ADU) in Des Moines, Iowa!

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Check out our new Accessory Dwelling Unit (ADU) in Des Moines, Iowa

Check out our new Accessory Dwelling Unit (ADU) in Des Moines, Iowa

Play Video
A new Accessory Dwelling Unit in Des Moines, Iowa - Just the reveal!

A new Accessory Dwelling Unit in Des Moines, Iowa - Just the reveal!

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Benefits of Accessory Dwelling units

  • Provide a more affordable housing option.

  • Integrate additional housing into a neighborhood with minimal impact (gentle density).

  • Make efficient use of existing infrastructure.

  • Increase property values and tax revenue.

  • Reduce urban sprawl.

  • Generate income for homeowners.

  • Support multi-generational households.

Commonly asked questions about ADUs

Who are ADUs for?

ADUs provide a flexible housing option that can evolve with families through all phases of life. Homeowners can rent them for additional income. They could be a place for an adult child to live after college. Or for an aging parent to live independently in retirement-the options go on from there.

Can I build an ADU?

Your local government's zoning policy typically determines whether you can build an ADU at your property and what the requirements are for doing so.


While multiple Greater Des Moines communities allow ADUs in some form, their policies can vary widely.  It's always best to contact your city's community development or building permitting officials to ask about policies near you.

New survey sheds light on local ADU policy

In fall 2023, we asked Greater Des Moines cities for basic information about their current policies to allow ADUs. 12 local governments responded.
Where are ADUs allowed?

The communities listed below responded that they allow ADUs in at least some areas.


Below, "by right" approval means a homeowner would predominantly work with city staff for the ADU to be approved. "Conditional" approval means a conditional use permit or similar approval must be issued, which usually involves a vote by a zoning board of adjustment or other local body.

By Right
Des Moines
Pleasant Hill
Polk County*

* Polk County in the table refers to unincorporated areas of the County that are not part of any city.

Policy trends

Local policies for ADUs vary widely, but here are some current trends to expect based on our survey:

  • The size of the ADU is usually limited (cities vary between 650 sq. ft. and 1,200 sq. ft.) and the ADU must generally be smaller than the main residence.​

  • While ADUs come in all shapes and sizes, your community may require your ADU to be attached to the main residence, not a stand-alone building. Or you may be required to build an ADU that matches the main house in look and style.

  • Several communities say they'll allow shared utility connections between the main house and the ADU. You will want to check policies from your local utilities as well. 

  • Expect to need off-street parking for your ADU. You will typically need at least 1 or 2 spaces on top of what is required for the main house.

  • While ADUs can often be rented, cities may require a rental certificate for either the main house or the ADU to always remain owner-occupied.

Always contact your local government's community development or building officials for complete information about local policies.

Are ADUs really "affordable housing"?


ADUs can cost between $50,000 and $150,000+ to add to a house, and they may rent at prices that are beyond the reach of people struggling most to afford the place they live. But ADUs do provide a new housing option that matches well with existing neighborhoods where it might otherwise be difficult to build.

Another benefit of ADUs is the land they sit on is already paid for - and they make good use of existing community infrastructure like roads, utilities, parks and more while providing a housing option many neighbors may never even notice.

ADU Community Resources

In 2022, the City of Des Moines dramatically expanded where ADUs are allowed to be constructed, increasing their potential as a housing solution in our community.

Here's where you can learn more about this housing option:

Local contacts


Here's who to call for ADU information in several Central Iowa communities.

Altoona: John Shaw, Community Development Director, 515-957-5114

Ankeny: Community Development Department; 515-963-3550

Clive: Community Development Department, 515-223-6221

Des Moines: Zoning Enforcement Division,, 515-283-4207

Indianola: Community Development Department, 515-961-9430

Johnston: Community Development Department, 515-727-7778

Norwalk: Community Development Department; 515-981-9530

Pleasant Hill: Madeline Sturms, Assistant City Mgr., 515-309-9464

Polk County*: Public Works Department; e-mail publicworks@

Urbandale: Community Development Dept.; 515-278-3935

Waukee: Community Development Department; 515-978-9533

West Des Moines: Linda Schemmel, Development Coordinator, 515-222-3620

Is your city not listed? Contact City Hall and ask to speak with the community development department or someone who handles building permitting issues.

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