Accessory Dwelling Units

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The City of Missoula adopted an update to our zoning code (Title 20) on October 19. This update included changes to standards and restrictions on Accessory Dwelling Units (ADUs), many of which are based on the implementation recommendations in "A Place to Call Home." Click on the Important Links widget on the sidebar of this page to see Title 20, and ask a question of a city planner in the Q & A bar below!

What is an Accessory Dwelling Unit?

Accessory Dwelling Units, known as ADU's, are small interior apartments or separate backyard houses that share a parcel with a single-family residence even if the density limit through zoning would otherwise not allow another housing unit on that property. ADU's are also known as mother-in-law apartments or backyard cottages. ADU's are called 'accessory' because they are lesser in size and presence to the primary dwelling on a property. The difference between an 'accessory' and any other dwelling unit is that an ADU stays at that accessory scale, as opposed to more primary dwelling units on the same property (i.e., a duplex), which would be permitted only if they were still within the density range allowed by zoning.

Why Do ADUs Matter?

The City of Missoula adopted "A Place to Call Home," our citywide housing policy in 2019. The policy recommends use of Accessory Dwelling Units in order to provide affordable, accessible housing that could be easily distributed throughout the city. ADU's provide a wide range of benefits, including supplemental income to finance-burdened home owners, affordable housing options for students and young families, a type of residential infill that is compatible with existing neighborhoods, and the ability for families to provide live-in options for aging parents or adult children needing extra care or services. The implications of the COVID-19 pandemic especially illustrate how the benefits of caring for aging parents at home rather than in long-term care facilities may further spur the demand for ADU-type living arrangements. For more information on the benefits of ADUs, see Important Links to the right for articles and resources.

Where Can You Build an ADU?

The City of Missoula allows ADU's in all residential zoning districts within the city limits. (NOTE: This does not include Special Districts). ADU's in the city are held to certain size and design standards, which have changed over time as the community's concerns and perceptions of ADU's have evolved. Adding an ADU to your property requires building permit review and approval.

The City currently allows three types of ADU's:

  • Internal ADU - created within an existing or new house. For example, a basement apartment.
  • Internal Addition ADU - added to the floor area of an existing house.
  • Detached ADU – a dwelling unit that is separate from the primary dwelling unit. For Example, a garage apartment or alley house.

The City of Missoula adopted an update to our zoning code (Title 20) on October 19. This update included changes to standards and restrictions on Accessory Dwelling Units (ADUs), many of which are based on the implementation recommendations in "A Place to Call Home." Click on the Important Links widget on the sidebar of this page to see Title 20, and ask a question of a city planner in the Q & A bar below!

What is an Accessory Dwelling Unit?

Accessory Dwelling Units, known as ADU's, are small interior apartments or separate backyard houses that share a parcel with a single-family residence even if the density limit through zoning would otherwise not allow another housing unit on that property. ADU's are also known as mother-in-law apartments or backyard cottages. ADU's are called 'accessory' because they are lesser in size and presence to the primary dwelling on a property. The difference between an 'accessory' and any other dwelling unit is that an ADU stays at that accessory scale, as opposed to more primary dwelling units on the same property (i.e., a duplex), which would be permitted only if they were still within the density range allowed by zoning.

Why Do ADUs Matter?

The City of Missoula adopted "A Place to Call Home," our citywide housing policy in 2019. The policy recommends use of Accessory Dwelling Units in order to provide affordable, accessible housing that could be easily distributed throughout the city. ADU's provide a wide range of benefits, including supplemental income to finance-burdened home owners, affordable housing options for students and young families, a type of residential infill that is compatible with existing neighborhoods, and the ability for families to provide live-in options for aging parents or adult children needing extra care or services. The implications of the COVID-19 pandemic especially illustrate how the benefits of caring for aging parents at home rather than in long-term care facilities may further spur the demand for ADU-type living arrangements. For more information on the benefits of ADUs, see Important Links to the right for articles and resources.

Where Can You Build an ADU?

The City of Missoula allows ADU's in all residential zoning districts within the city limits. (NOTE: This does not include Special Districts). ADU's in the city are held to certain size and design standards, which have changed over time as the community's concerns and perceptions of ADU's have evolved. Adding an ADU to your property requires building permit review and approval.

The City currently allows three types of ADU's:

  • Internal ADU - created within an existing or new house. For example, a basement apartment.
  • Internal Addition ADU - added to the floor area of an existing house.
  • Detached ADU – a dwelling unit that is separate from the primary dwelling unit. For Example, a garage apartment or alley house.

Are you interested in building an ADU? Have questions about city code related to ADUs? City Development Services staff are here to answer your questions!

What questions do you have about Accessory Dwelling Units?

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    Hi, Are the amended changes in affect now? Will they allow a garage with a 600sf upstairs apartment with a height restriction of 25ft? Thank you, Nancy Wagner

    Wagner asked 4 months ago

    Hello Nancy, thanks for your questions. The new regulations related to Accessory Dwelling Units are in effect as of November 18, 2020 and can be found here. An amendment was adopted that would allow a detached garage with a 600 square foot ADU on top to have a maximum structure height of 25 feet. To discuss project and property-specific questions, please reach out to our zoning desk by emailing: cityzoner@ci.missoula.mt.us. Thanks again for your note and we apologize for the delayed response! 

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    Hi, My name is Lewis Dortch, I live at 1910 S. 12th St. W. in Missoula. My question about ADU's is with parking. I was reading that for a detached ADU there needs to be at least 1 off street parking spot. Does that also apply if you were to build an Internal Addition ADU or Internal ADU? Thanks for the help!

    Lewis Dortch asked 5 months ago

    Hi Lewis - thanks for your question. The most recently adopted amendments to Title 20 do not require any new ADU to provide an additional parking space for that unit.  If existing required parking is displaced in the creation of an ADU, that existing parking must be relocated on site and must meet any required standard.  Feel free to reach out to City zoning staff to talk about any other property or project-specific questions at cityzoner@ci.missoula.mt.us.

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    This is not a question but rather a comment. The police dept is dealing with increased challenges related to parking and ADA. When the City takes away parking for vehicles and allocates bike parking it shifts the enforcement to law enforcement, limits their abikity to solve the problem. We live in Montana and while people bike to work during the spring and summer they almost always drive duting the winter. We shouldnt decrease parking for allowable biking except in commercial apt developments. Not residential

    CO55 asked 8 months ago

    Thank you very much for your comment!