Building a casita (ADU) in Tucson
City code and Arizona law · Last reviewed October 9, 2026
Tucson lets you build two casitas, or accessory dwelling units (ADUs), on a lot with one existing home, and a third on lots over one acre if one casita is deed-restricted as affordable housing. A casita can be up to 650 square feet, or up to 75% of your home's floor area (capped at 1,000 square feet) if that is larger. It needs 5-foot side and rear setbacks, no parking, and a building permit from Planning and Development Services (PDSD). The city's updated rules took effect on November 21, 2024, to meet Arizona's ADU law. [1][2]
| How many casitas | Two on a lot with one existing home; a third on lots over one acre if one is deed-restricted affordable; one on a lot with a duplex [1] |
|---|---|
| Where allowed | Zones that allow residential uses; not on multifamily or commercial sites [1] |
| Max size | 650 sq ft, or 75% of the main home's gross floor area up to 1,000 sq ft, whichever is larger; must also fit your zone's lot coverage limit [1] |
| Height | Same as a single-family home in your zone (generally 25 ft) [1] |
| Setbacks | 5 ft minimum side and rear; a detached casita can't go in the front yard [1] |
| Parking | None required [1][2] |
| Lot coverage | Usually 70% to 80% of the lot, depending on zone; buildings, driveways and storage areas count [1] |
| Utilities | May share the main home's utilities (an upgrade may be needed) or have separate meters [1][6] |
| Cool roof | Required on newly built casitas [1] |
| Address | Each casita needs its own address, issued by Pima County [1] |
| Pre-approved plans | Casita Model Plan Library: city pre-reviewed plans from about 156 to 1,000 sq ft, bought from the designers [9] |
| Plan review target | 30 days for new building permits (Standard Lane goal) [8] |
On this page
What you can build in Tucson
Tucson has allowed casitas in zones that allow residential uses since January 2022. The Mayor and Council adopted new rules on October 22, 2024, effective November 21, 2024, to meet Arizona's ADU law. The changes raised the number of casitas allowed per lot, changed how maximum size is figured, adjusted height limits, removed parking minimums and changed setbacks.
Under the current rules:
- You can build two casitas on a lot with one existing home.
- A third casita is allowed on parcels over one acre, but one casita must be deed-restricted as affordable housing, meaning affordable to households earning 80% of area median income or less.
- You can build one casita on a lot with a duplex.
- Casitas are not allowed in zones without residential uses, such as industrial zones, or on multifamily or commercial sites.
A casita can be attached, detached or a garage conversion. It can have its own kitchen, entrance, bathroom, living and sleeping space, and it must sit on a permanent foundation. Casitas don't count toward your zone's residential density. When you build on a lot with an existing, occupied home, commercial standards don't apply. If you build three or more units on a parcel without an existing occupied home, commercial standards may apply. [1][2][3]
Size, height and setbacks
Size. A casita can be up to 650 square feet, or 75% of the main home's gross floor area up to 1,000 square feet. So if your house is smaller than 867 square feet, your casita can still be 650 square feet. The city's examples: an 800 sq ft home allows a 650 sq ft casita, and a 1,100 sq ft home allows an 825 sq ft casita.
Lot coverage. Everything that covers the lot counts: the house, garage, the casita, storage areas and vehicle areas, paved or not. In most zones the limit is 70% to 80% of the lot. Check your zone in UDC 6.3, Dimensional Standards.
Height. A casita can be as tall as a single-family home in the same zone, which the city says is generally 25 feet.
Location and setbacks. A freestanding casita can go in the rear or side yard, but not the front yard. The minimum side and rear setback is 5 feet. That matches the state cap: Arizona law says a city may not require side or rear setbacks of more than 5 feet for an ADU. For small changes to setbacks, you can ask for a Design Development Option (DDO), a separate application under UDC 3.11.1. [1][4][5]
Parking, utilities and addresses
Tucson has no parking requirement for casitas. State law also bars a covered city from requiring extra parking for an ADU or a fee instead of parking.
Separate utility requirements don't apply to casitas. Your casita can share utilities with the main house, though an upgrade may be needed, or it can have its own meters. Utility sizing must meet the building code for all the buildings served, and you must show enough information to justify it.
Each casita needs its own address, issued by Pima County. [1][4][6]
Building code rules
Tucson's Building Official set out the building code standards for ADUs in Administrative Policy 2022.01-IE, revised February 20, 2025:
- An ADU attached to another dwelling unit needs at least one-hour fire-rated separation if the building has no sprinklers.
- Buildings with 3,600 square feet or more of roof area, counting carports and porches, need a fire review and "may be required to have an automatic fire sprinkler system," the policy says. Arizona's ADU law (ARS 9-461.18, subsection D) says building and fire codes still apply, "except that a municipality may not require an accessory dwelling unit to ... contain a fire sprinkler." If your project is that large, confirm with the Building Official how Tucson applies this.
- Newly built ADUs must meet the Inclusive Home Design Ordinance and future solar preparation rules.
- Newly built ADUs with a washing machine in a room with an exterior wall need gray water piping.
- Separate electric vehicle charging isn't required.
New casitas also need a cool roof. [1][4][6]
Garage conversions
You can convert a garage into a casita. Casitas made by altering existing, permitted structures, such as guesthouses, garages or sheds, don't have to meet the solar, gray water and EV charging requirements for new construction. The structure must still be improved as needed to provide fire separation under the residential code. Ask PDSD about your structure before you design. See our garage conversion guide. [1][6]
Fees and timeline
Tucson charges building permit fees and one-time development impact fees for roads, parks, police and fire. PDSD collects impact fees when the building permit is issued, based on the service area, the use and the size of the project. Use the city's Development Impact Fee Calculator for an estimate. The city says it is updating its impact fee program and has posted proposed 2025 fees, so check the Development Impact Fees page for current amounts.
New building permits go into PDSD's Standard Lane, which has a 30-day review goal. The city's Permit Dashboard shows current review times, updated daily. For budgeting, see our ADU cost guide and ADU permit process guide. [7][8]
Pre-approved casita plans
The Casita Model Plan Library lists plans that PDSD has pre-reviewed. Most came from the city's Casita Model Plan Design Competition. You buy a plan from its designer, using the contact details in the library, and you still need a site plan for your lot covering zoning and utility locations. Only plans not marked "Pending Approval" are already approved.
The listed designs range from a 156 sq ft studio (MICRO-MINI) to a 1,000 sq ft two-bedroom (Lumen), with many one-bedroom options between about 540 and 830 square feet.
Arizona law (ARS 9-461.20) also requires cities to set up pre-approved housing plans or a pre-approved plan program. Beginning July 1, 2026, that includes at least three pre-approved ADU plans, each 200, 600 or 1,000 square feet. Ask PDSD how Tucson's library fits this law. See our prefab ADU guide for factory-built options. [9][10]
Renting your casita
Arizona law bars Tucson from stopping you from renting the house and a casita separately on long-term leases of 90 days or more, or month to month. The city also can't require the casita's tenant to be related to you or employed by you.
State law says a city "may not prohibit vacation rentals or short-term rentals," but it may require a local permit, with a fee of no more than the cost of issuing it or $250, whichever is less. If your casita's certificate of occupancy or similar final approval was issued on or after September 14, 2024, a city may require you to live on the property to rent short term. Ask PDSD what Tucson currently requires.
Tucson's group dwelling rules bar 5 or more unrelated people from living in one home. In R-1 zones, 5 or more unrelated people can't live on the same lot. [1][4][11]
Permit steps in Tucson
Confirm your lot is in the city and its zone
Look up your property on Map Tucson or Property Research Online. If it is outside city limits, Pima County's rules apply instead. Your zone must allow residential uses. [1][8]
Work out size and lot coverage
Your casita can be 650 square feet, or 75% of your home's gross floor area up to 1,000 square feet. Add up your house, garage, driveways and parking areas, storage areas and the new casita, and check the total against your zone's lot coverage limit in UDC 6.3. [1]
Design the casita or pick a model plan
Hire a designer, or buy a pre-reviewed plan from the Casita Model Plan Library. Even with a model plan, you need a site plan for your lot. Check the 5-foot side and rear setbacks, height and cool-roof rules. [1][9]
Check historic or neighborhood preservation rules
In a Historic Preservation Zone, Neighborhood Preservation Zone or on a historic landmark, follow those zones' standards too. Any development there needs a permit and a historic preservation design review. [1][8]
Apply for a building permit online
Submit a residential plot plan, a floor plan and construction documents through Tucson Development Center (TDC) Online. The TDC Online Navigator helps you pick the right permit type. [1][8]
Plan review and fees
New building permits are in PDSD's Standard Lane, with a 30-day review goal. Development impact fees are collected when the building permit is issued. [7][8]
Build and pass inspections
The work must be done by a licensed contractor or by you as the homeowner. Schedule inspections through TDC Online. [1][8]
Pre-approved and sample plans
Casita plans pre-reviewed by PDSD, from design-competition winners and other designers, sized from a 156 sq ft studio to a 1,000 sq ft two-bedroom; you buy them from the designer and add your own site plan. [1][9]
Who to call
-
Planning and Development Services (PDSD)
Casita zoning, building permits, plan review and inspections
201 N Stone Ave, Tucson, AZ 85701
-
Zoning questions about your lot: zone1.desk@tucsonaz.gov
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Permit process questions: pdsdinquiries@tucsonaz.gov
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Building code standards for ADUs (fire separation, utilities)
Questions people ask
How big can a casita be in Tucson?
Up to 650 square feet, or 75% of your home's gross floor area up to 1,000 square feet. It must also fit within your zone's lot coverage limit, usually 70% to 80% of the lot. [1]
How many casitas can I build in Tucson?
Two on a lot with one existing home. A third is allowed on parcels over one acre if one casita is deed-restricted as affordable housing. A lot with a duplex can have one casita. [1]
How close to the property line can a casita be in Tucson?
The minimum side and rear setback is 5 feet, and a detached casita can't go in the front yard. A Design Development Option application may allow smaller setbacks in some cases. [1]
Do I need to add parking for a casita in Tucson?
No. Tucson has no parking requirement for casitas, and state law bars covered cities from requiring extra parking for an ADU. [1][4]
Can I build my own casita in Tucson?
Tucson says construction must be done by a licensed contractor or the homeowner. You still need a building permit and inspections. See our hiring ADU help guide. [1]
Does Tucson have free casita plans?
Tucson's Casita Model Plan Library has plans pre-reviewed by the city, but you buy them from the designers. You still need your own site plan. [9]
Sources (11)
- Want to Build a Casita? (Casitas in Tucson, 5/19/2025), City of Tucson Planning and Development Services. Accessed October 9, 2026.
- Accessory Dwelling Units Code Amendment, City of Tucson Planning and Development Services. Accessed October 9, 2026.
- Casitas in Tucson, City of Tucson Planning and Development Services. Accessed October 9, 2026.
- 9-461.18. Accessory dwelling units; regulation; applicability; definitions, Arizona State Legislature. Accessed October 9, 2026.
- Unified Development Code: Summary of Dimensional Standards (July 2020), City of Tucson Planning and Development Services. Accessed October 9, 2026.
- Administrative Policy 2022.01-IE: Building Code Standards for Accessory Dwelling Units (revised Feb. 20, 2025), City of Tucson Planning and Development Services. Accessed October 9, 2026.
- Development Impact Fees, City of Tucson Planning and Development Services. Accessed October 9, 2026.
- Planning & Development Services, City of Tucson. Accessed October 9, 2026.
- Casita Model Plan Library, City of Tucson Planning and 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.
- 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.