Accessory Dwelling Units (ADUs)
An Accessory Dwelling Unit (ADU) is a secondary dwelling unit that provides living, sleeping, eating, cooking, and sanitation facilities on the same lot as a primary residence. It can be attached to or integrated with the primary residence or built separately as a detached structure in the backyard.
Frequently Asked Questions
Can a recreational vehicle (RV) or mobile home be used as an ADU?
No. Manufactured homes, recreational vehicles (RV), and trailers cannot be used as an ADU. This includes “Tiny Homes” built on chassis with wheels.
How does an ADU differ from a standard home addition?
Unlike a typical home addition, an ADU is a fully self-contained living space complete with its own bathroom, bedroom, and kitchen that functions independently from the primary dwelling. It maintains a separate entrance and has no internal connection to the main home, allowing occupants to come and go without passing through the primary residence.
Where are ADUs allowed in Mesa?
ADUs are permitted on any lot where a single residence is allowed, including lots zoned Agricultural (AG), Single Residence (RS), Small Lot Single Residence (RSL), Multiple Residence (RM), Downtown Residence (DR), Mixed Use (MX), Neighborhood Commercial (NC), Limited Commercial (LC), and General Commercial (GC).
How many ADUs can I have on my property?
Any property with an existing single residence is permitted to have one attached and one detached ADU. An additional detached ADU is permitted on lots that are over an acre in size if at least one ADU on the property is a restricted-affordable dwelling unit.
What is a restricted-affordable dwelling unit?
A restricted-affordable dwelling unit is one that will be rented or sold to households earning up to 80% of the area median income, as stipulated by a deed restriction or development agreement with Mesa.
How large can my ADU be?
1,000 square feet or 75% of the habitable floor area of the primary dwelling unit, whichever is less.
How do I determine the habitable floor area?
Habitable floor area is the interior space in a building used for everyday purposes — things like living, sleeping, eating, cooking, sanitation, conditioned storage, and recreation. Space used only for unconditioned storage or parking does not count.
What are the required setbacks for ADUs?
An ADU must be set back at least five (5) feet from the side and rear property lines. The front and street side setbacks must comply with the requirements for the underlying zoning district.
If a garage, unconditioned storage room, workshop, or similar uninhabitable space is attached to the ADU, additional setback rules apply. For an attached ADU, that uninhabitable space must meet the setback requirements for the underlying zoning district. For a detached ADU, that uninhabitable space must meet the setback requirements for detached accessory buildings under Section 11-30-17 of the Zoning Ordinance.
How tall can my ADU be?
An attached or detached ADU must comply with the height requirements for the underlying zoning district. For detached ADUs, any uninhabitable space — such as a garage, unconditioned storage room, or workshop — that is part of the structure must meet the height requirements for detached accessory buildings under Section 11-30-17 of the Zoning Ordinance. For details on the maximum allowable height in different zoning districts, please refer to the Mesa Zoning Ordinance.
I have a single-story house. Can I build a two-story detached ADU in the backyard?
Yes. The height of ADUs is regulated by the maximum height allowed for single-family homes in your zoning district.
Is additional parking required for an ADU?
No. You do not need to add parking spaces for an ADU, but your property must still maintain at least two parking spaces for the primary residence.
Do I need a building permit to build an ADU?
Yes, a building permit will be required. The plan set should include a site plan, code data sheet with scope of work, architectural, structural, electrical, plumbing & mechanical plans, specifications, and calculations, as applicable for the proposed work. Learn more about Commercial Construction / Residential Construction
I live in a neighborhood controlled by an HOA. Can I build an ADU on my property?
You will need to check your HOA’s Covenants, Conditions and Restrictions (CC&Rs). HOAs can restrict or regulate ADUs through CC&Rs and these agreements are separate from the Mesa’s zoning regulations.
Can I rent my ADU as a short-term rental (Airbnb, VRBO, etc.)?
Yes. A Short-Term Rental License is required if the unit is rented for 29 days or fewer at a time. Learn more about Short Term Rental Licenses.
Can I sell the ADU separately from the primary residence?
No. The ADU may not be sold separately from the primary residence.
Can my ADU be constructed without utility connections?
No. An ADU must be provided with water, sewer, and electric utilities.
Can my ADU have separate utility meters?
Yes. An ADU may have separate meters or sub-meters for water, sewer, and electric utilities, but permits are required.
I live in a Historic District. Are there different requirements for ADUs?
No. These requirements apply to all eligible residential properties, including those within a historic district. If your lot is in a Historic District, you will need a Certificate of Appropriateness from the Historic Preservation Office before you can be approved for a building permit. To learn more about the Certificate of Appropriate requirement, please visit Historic Preservation.