Accessory Dwelling Unit (ADU) Model Plans Pilot Program

Information item only with an opportunity to provide comments. Staff is also seeking a member of the Housing Commission to volunteer to serve on an ADU Model Plans Selection Committee and provide programmatic advice as part of the process to solicit ADU pre-approved model plans.  

Through the ADU Model Plans Pilot Program, the City of Flagstaff aims to increase the number of ADUs in Flagstaff by reducing barriers to building ADUs. Program goals include:  

1. Increase awareness of ADUs and their benefits to the Flagstaff community 

2. Create an ADU Model Plans Library to host a growing inventory of pre-approved ADU model plans  

3. Increase ADUs in Flagstaff by simplifying the process and reducing the costs to design and permit ADUs 

4. Connect interested homeowners with design professionals and other ADU resources 

ADUs are important to the City’s adopted Carbon Neutrality Plan and 10-Year Housing Plan because they are generally smaller, more affordable housing units in existing neighborhoods with access to existing infrastructure and transportation networks. ADU model plans libraries are becoming increasingly common tool among cities and counties across the U.S. to encourage the development of ADUs and increase the supply of housing; the City of Tucson provides a good example of an ADU model plans library in Arizona: Casitas in Tucson (tucsonaz.gov). 

The City of Flagstaff started this process by seeking input from design and construction professionals and the Flagstaff community on barriers to building an ADU. This research identified the major barriers to be: 1) costs of construction, 2) city design standards, 3) cost of designing an ADU, 4) finding a designer, 5) navigating the design and permitting process, and 6) City permitting fees.  

To address some of these barriers, the City will invite design and construction professionals in fall 2024 to submit detached ADU designs. The designs will be required to meet specific sustainable design criteria, such as all-electric, energy-efficient construction, and may also include different design categories (size, features, etc.) and other design requirements. A selection committee comprised of design and construction professionals, community partners, and City staff will choose winning designs; winners will submit full construction plans by early 2025. Winners who submit full construction plans by the deadline will receive a cash prize. All ADU model plans will be reviewed for building code and design criteria compliance before becoming part of the library.  

Flagstaff community members will be able to preview the floor plans and elevations for the pre-approved model ADU plans in the library and contact the designer to select a design. They will work with the designer to gain full access to the plans, ensure the plans are suitable for their site, and navigate the Building Permit review and approval process. The building permit review process for pre-approved ADU model plans will ideally be shorter, less expensive, and easier to navigate than a custom plans review.