Building an ADU (casita) in Mesa
City code and Arizona law · Last reviewed October 9, 2026
Mesa allows one attached and one detached accessory dwelling unit (ADU, or casita) on any lot where a single residence is allowed, and a third on lots of an acre or more if one is restricted-affordable. Each ADU can be 75% of the main home's interior habitable area or 1,000 square feet, whichever is less, with 5-foot side and rear setbacks and the same height limit as the house. No extra parking is required. You need a building permit from Development Services, applied for online in DIMES. [1][2][3]
| How many | One attached and one detached ADU; one more detached ADU on lots of 1 acre or more if one ADU is restricted-affordable [1] |
|---|---|
| Where allowed | Any lot where a single residence is allowed (AG, RS, RSL, RM, DR, MX, NC, LC and GC zones), and any lot with an existing single residence [1][2] |
| Max size | 75% of the main home's interior habitable area or 1,000 sq ft, whichever is less [1] |
| Minimum lot size | None [1] |
| Setbacks | 5 ft side and rear; front and street side same as the main home [1] |
| Height | Same as the main home in your zoning district; a two-story detached ADU is allowed [1][2] |
| Parking | No additional spaces; a converted garage or carport's covered parking doesn't have to be replaced [1] |
| Utilities | Water, sewer and electric required, from the same providers as the main home; separate meters or sub-meters allowed with permits [1][2] |
| Not allowed as ADUs | Manufactured homes, RVs, trailers and tiny homes on wheeled chassis [1][2] |
| Plan review | Comments or approval within 10 working days (5 with paid expedited review) [3] |
| Short-term rental | Allowed with a Mesa Short-Term Rental License ($250 a year) [2][9] |
| Selling separately | Not allowed [2] |
On this page
What you can build in Mesa
Mesa's ADU rules are in Zoning Ordinance Section 11-31-3, last amended March 9, 2026, under Arizona's ADU law. There is no minimum lot size for an ADU.
- One attached ADU and one detached ADU are allowed on a lot in any Agricultural, Residential, Commercial and Mixed Use, or Downtown district where a single residence is allowed. A lot with an existing single residence gets the same right in any district.
- One more detached ADU is allowed on a lot of one acre or more if one ADU is restricted-affordable: rented to households earning up to 80% of area median income through a deed restriction or a development agreement with the city.
An ADU must have its own separate entrance and no internal connection to the main house. It can have a partial or full kitchen, but only one. It must meet the building code for homes. Manufactured homes, RVs and trailers can't be ADUs, including tiny homes built on a chassis with wheels. See our backyard tiny house guide. [1][2]
Size, height and setbacks
Size. An ADU's interior habitable area can't exceed 75% of the main home's interior habitable area, or 1,000 square feet, whichever is less. Habitable area means space for living, sleeping, eating, cooking, sanitation, conditioned storage and recreation. Unconditioned storage and parking don't count. The ADU must also fit your district's lot coverage and building coverage limits.
Setbacks. A new attached or detached ADU needs at least 5 feet from side and rear property lines. Front and street side setbacks are the same as for the main home. A garage, unconditioned storage room or workshop attached to the ADU follows other rules: the zoning district's setbacks for an attached ADU, or the detached accessory building rules in Section 11-30-17 for a detached one.
Height. An ADU can be as tall as the main home is allowed to be in your district, so a two-story detached ADU is allowed even behind a one-story house. Uninhabitable space attached to a detached ADU must meet the accessory building height rules. [1][2]
Converting a garage or existing building
You can convert an existing detached accessory building, such as a detached garage, into an ADU without meeting the new 5-foot setbacks, even if the building is legally non-conforming. Any expansion must meet the 5-foot setbacks or, for a non-conforming building, stay in line with the existing setback without making the non-conformity worse.
You can also convert part of your house into an ADU with no extra setbacks. A ground-floor addition for the ADU needs the 5-foot setbacks. A second-story addition needs the main home's setbacks.
If you convert a garage or carport, you don't have to replace the covered parking elsewhere on the lot. Mesa's ADU page adds that the property must still keep at least two parking spaces for the main house. See our garage conversion guide. [1][2]
Parking and utilities
No additional parking spaces are required for an ADU, matching the state law ban on extra parking. Mesa's ADU page says the property must still have at least two parking spaces for the main house.
An ADU must have water, sewer and electric service from the same providers as the main house. It can have separate meters or sub-meters, but they need permits. You can't build an ADU on a current or planned public utility easement without written consent from every utility that uses or may use it. [1][2][4]
Fees and timeline
Mesa's Development Services fee schedule (updated July 2026) sets the building permit fee by applying the project's total valuation to a residential rate table. For new homes and additions, livable area is valued at the current ICC construction cost per square foot, and non-livable area at half that. For accessory buildings and remodels, the valuation is what you state, verified by the plans examiner. Those fees don't include impact fees or other fees that may apply. Expedited review adds 100% of the total permit fee.
Staff send comments or approval within 10 working days, and later reviews follow the same timeline. Ask Permit Services at 480-644-4273 for a fee estimate. For budgeting, see our ADU cost guide and ADU permit process guide. [3][5]
Pre-approved ADU plans
Under state law, Mesa runs a Preapproved Housing Design Plan Program. It accepts ADU plans of 200, 600 or 1,000 square feet, plus single-family, duplex and triplex plans. Designers pay no fee to submit plans for review.
Approved plans are posted in the city's Standard Plan Library with the designer's contact details. To use one, you license it from the designer, and you both sign the city's Preapproved Housing Design Plan Agreement and submit it to Permit Services. Any fee for the plan is between you and the designer, and standard permit fees still apply. You may also need a plot plan, site plan, grading and drainage plan or off-site improvement plans. Plans marked "IN REVIEW" aren't available yet. See our prefab ADU guide for other ready-made options. [6][7][8]
Renting your ADU
State law bars Mesa from stopping you from renting the house and the ADU separately on leases of 90 days or more, or requiring the tenant to be related to you.
Mesa's ADU page says you can rent an ADU short term. You need a Short-Term Rental License for stays of 29 days or less. It costs $250 a year, is issued only to the deeded owner, and requires an Arizona transaction privilege tax license and proof of at least $500,000 in liability insurance. Mesa's ADU and license pages don't mention an owner-occupancy rule for ADUs. State law lets a city require one for an ADU whose final approval was issued on or after September 14, 2024, so confirm with Mesa Licensing.
You can't sell an ADU separately from the main house. [2][4][9][10]
Permit steps in Mesa
Confirm your zoning with Planning
Check that your lot is in Mesa (not a county island) using the Explore Mesa map, then contact the Planning Division at Planning.Info@MesaAz.gov or 480-644-4726 to confirm your project is allowed. [3][9]
Check HOA, historic and flood rules
Read your HOA's CC&Rs, which can restrict ADUs separately from zoning. In a historic district, get a Certificate of Appropriateness from the Historic Preservation Office first. In a flood zone, get approval from the Maricopa County Flood Control District before you apply. [2][3]
Design the ADU or license a pre-approved plan
Design to Section 11-31-3 of the zoning ordinance, or license a plan from Mesa's Standard Plan Library from its designer. [1][7]
Check whether you need a licensed contractor
Owner-occupied projects may not require a licensed contractor. Check the state contractor licensing law and complete the city's Contractor Licensure Verification Form. [3]
Apply online in DIMES
Apply for a residential construction permit in DIMES. Upload a site plan, a code data sheet with the scope of work, and architectural, structural, electrical, plumbing and mechanical plans, with specifications and calculations as needed. [2][3]
Plan review
Staff send written comments or approval within 10 working days (Monday to Thursday, excluding holidays). Expedited 5-day review costs extra. Resubmittals follow the same timeline. [3]
Pay fees and get the permit
Once your plans are approved you get a fees-due email. Fees are based on estimated construction cost, and full payment is required before the permit is issued. [3]
Build and pass inspections
Schedule construction inspections through Development Services until the permit is complete. [3]
Pre-approved and sample plans
Preapproved Housing Design Plan Program and Standard Plan Library
Pre-approved plans for ADUs of 200, 600 or 1,000 sq ft and for homes, licensed from the designer with a signed city agreement; plans marked "IN REVIEW" aren't available yet. [6][7]
Who to call
-
Development Services, Planning Division
Zoning questions and whether an ADU is allowed on your lot: Planning.Info@MesaAz.gov
55 N. Center Street, Mesa, AZ 85201
-
Development Services, Permit Services
Building permits, fees and pre-approved plans: PermitServices@mesaaz.gov
-
Short-Term Rental Licenses
Questions people ask
How big can an ADU be in Mesa?
75% of your home's interior habitable area or 1,000 square feet, whichever is less. It must also fit your district's lot and building coverage limits. [1]
Can I build a two-story ADU behind a one-story house in Mesa?
Yes. Mesa limits ADU height to what your zoning district allows for the main house, not the height of your existing home. [1][2]
Do I need to add parking for an ADU in Mesa?
No additional spaces are required, and if you convert a garage or carport you don't have to replace its covered parking. Mesa says the property must still keep at least two parking spaces for the main house. [1][2]
Can I put a tiny house on wheels in my Mesa backyard as an ADU?
No. Manufactured homes, RVs, trailers and tiny homes built on a chassis with wheels can't be used as ADUs in Mesa. [1][2]
Can I Airbnb my casita in Mesa?
Yes, with a Mesa Short-Term Rental License for stays of 29 days or less. The license costs $250 a year and needs an Arizona transaction privilege tax license. [2][9]
Can my HOA stop me from building an ADU in Mesa?
It can. Mesa says HOAs can restrict or regulate ADUs through their CC&Rs, separately from the city's zoning rules. Check your CC&Rs before you design. [2]
Sources (10)
- Mesa Zoning Ordinance, Section 11-31-3: Accessory Dwelling Unit, City of Mesa (Municode). Accessed October 9, 2026.
- Accessory Dwelling Units (ADUs), City of Mesa Development Services, Planning. Accessed October 9, 2026.
- Residential Construction, City of Mesa Development Services. Accessed October 9, 2026.
- 9-461.18. Accessory dwelling units; regulation; applicability; definitions, Arizona State Legislature. Accessed October 9, 2026.
- Schedule of Fees and Charges: Development Services (updated July 2026), City of Mesa. Accessed October 9, 2026.
- Preapproved Housing Design Plan Program, City of Mesa Development Services. Accessed October 9, 2026.
- Standard Plan Library, City of Mesa Development Services. Accessed October 9, 2026.
- 9-461.20. Municipal housing; standard preapproved housing design plans; indemnification; definition, Arizona State Legislature. Accessed October 9, 2026.
- Short-Term Rental License, City of Mesa Licensing. Accessed October 9, 2026.
- 9-500.39. Limits on regulation of vacation rentals and short-term rentals; state preemption; civil penalties; transaction privilege tax license suspension; definitions, Arizona State Legislature. Accessed October 9, 2026.