7.C.
Housing Commission
- Meeting Date:
- 04/23/2026
- From:
- Genevieve Pearthree, Senior Sustainability Planner
TITLE:
Flagstaff Accessory Dwelling Unit (ADU) Model Plans Library
STAFF RECOMMENDED ACTION:
Staff request ideas on ways to let Flagstaff community members know about the Library, as well as expand the ADU Model Plans Library and support the growth of ADUs in Flagstaff more broadly.
Executive Summary:
The City launched the Flagstaff Accessory Dwelling Unit (ADU) Model Plans Library in January 2026 at www.flagstaff.az.gov/ADUs. The Library contains 11 pre-approved, publicly viewable ADU model plans, with an additional plan under review. The plans were selected through a 2025 Request for Informal Proposals (RFIP), which attracted over 30 design proposals. A selection committee of community partners and City staff selected the 10 winning designs and several runners-up.
ADUs, also known as backyard homes or casitas, are important to the City’s housing and climate goals because these smaller housing units can offer lower rents and monthly utility costs, and increase Flagstaff’s housing supply in established neighborhoods. These units can also provide more flexible housing options for households of all sizes, generate supplemental rental income for homeowners, and increase housing availability in established neighborhoods.
Model plans are intended to lower the barriers to ADU construction in Flagstaff by reducing the cost to design an ADU, making it easier to find a designer, simplifying the design and permitting process, and providing access to lower City permitting fees for model plans (compared to City fees for custom plans). To build an ADU using a pre-approved model plan, Flagstaff community members can browse the Library, select their favorite plan, contact the designer to purchase access to the full plans, work with the designer to draft a site plan, and proceed through the City’s building permit review and approval process. Several of the ADUs offer pre-approved options, including floor plans, roof plans, foundation types, and exterior materials, for community members to choose from.
The plans are “pre-approved” because they have already undergone City of Flagstaff Building Plan review to confirm compliance with the City’s adopted building and fire codes. This means that when a property owner applies to use the plans for an individual lot, the City's review is limited to whether the ADU will meet relevant Zoning and other City design standards for that lot. Ideally, the City review process for pre-approved plans on a particular lot is shorter and less costly than a custom plan review.
The City of Flagstaff Zoning Code allows two ADUs (one detached and one attached) to be built on a property that already has a single-family home. Larger properties that provide affordable housing (that meet certain standards) are allowed one additional ADU. However, some Homeowners’ Associations (HOAs) have more restrictive Codes, Covenants, and Restrictions (CC&Rs) that ban or make it difficult to build an ADU in those neighborhoods.
The City is currently working to publicize the ADU Model Plans Library through virtual and printed means. Staff are also considering next steps to expand the Library and support the growth of ADUs in Flagstaff more broadly.
ADUs, also known as backyard homes or casitas, are important to the City’s housing and climate goals because these smaller housing units can offer lower rents and monthly utility costs, and increase Flagstaff’s housing supply in established neighborhoods. These units can also provide more flexible housing options for households of all sizes, generate supplemental rental income for homeowners, and increase housing availability in established neighborhoods.
Model plans are intended to lower the barriers to ADU construction in Flagstaff by reducing the cost to design an ADU, making it easier to find a designer, simplifying the design and permitting process, and providing access to lower City permitting fees for model plans (compared to City fees for custom plans). To build an ADU using a pre-approved model plan, Flagstaff community members can browse the Library, select their favorite plan, contact the designer to purchase access to the full plans, work with the designer to draft a site plan, and proceed through the City’s building permit review and approval process. Several of the ADUs offer pre-approved options, including floor plans, roof plans, foundation types, and exterior materials, for community members to choose from.
The plans are “pre-approved” because they have already undergone City of Flagstaff Building Plan review to confirm compliance with the City’s adopted building and fire codes. This means that when a property owner applies to use the plans for an individual lot, the City's review is limited to whether the ADU will meet relevant Zoning and other City design standards for that lot. Ideally, the City review process for pre-approved plans on a particular lot is shorter and less costly than a custom plan review.
The City of Flagstaff Zoning Code allows two ADUs (one detached and one attached) to be built on a property that already has a single-family home. Larger properties that provide affordable housing (that meet certain standards) are allowed one additional ADU. However, some Homeowners’ Associations (HOAs) have more restrictive Codes, Covenants, and Restrictions (CC&Rs) that ban or make it difficult to build an ADU in those neighborhoods.
The City is currently working to publicize the ADU Model Plans Library through virtual and printed means. Staff are also considering next steps to expand the Library and support the growth of ADUs in Flagstaff more broadly.