What's Required in Tucson
- Apply for the casita through TDC Online using the Accessory Dwelling Unit checklist under the 2024 I-Codes and Tucson amendments.
- Keep the casita within 75 percent of the primary structure and 1,000 square feet, or at most 650 square feet regardless of house size.
- Meet 5-foot rear and side setbacks or obtain a Design Development Option.
- Install a cool roof on a newly built casita.
- Obtain a separate address for the casita from Pima County.
- Submit full plans, including foundation, framing, energy, mechanical load calculations, plumbing and electrical with a panel schedule and load calculation.
- Pay development impact fees for parks, streets and police when the permit is issued.
- Complete historic review if the parcel is in a Historic or Neighborhood Preservation Zone.
- Use a licensed contractor if the casita will be rented; the owner-builder exemption covers owner-occupied work only.
Can you build an ADU in Tucson?
Yes. Tucson calls them casitas, and since November 21, 2024 the Unified Development Code has allowed them on parcels in any zone that permits residential use. The change brought the code in line with Arizona's ADU law (A.R.S. 9-461.18). The current city rules:
- Two casitas on a parcel with one existing family dwelling, or one casita with a duplex. A third casita is allowed on parcels over one acre if one unit is restricted to households earning 80% of area median income or less.
- Size: up to 75% of the primary structure, capped at 1,000 sq ft. Any casita can be up to 650 sq ft regardless of the house size.
- Height matches the single-family limit for the zone, generally 25 feet. Rear and side setbacks are 5 feet.
- No parking is required. A cool roof is required on a newly built casita. Each casita needs its own address issued by Pima County, but it may share the house's utility meters.
The city's casita rules have no owner-occupancy condition. State law bars cities from prohibiting long-term rental of an ADU, requiring a family or other relationship between owner and occupant, or demanding a restrictive covenant. Selling the casita separately requires a lot split, and both new lots must meet the minimum lot size. Parcels in unincorporated Pima County follow county rules instead.
| What you are doing | City filing | Rule |
|---|---|---|
| New detached casita | New Building/Dwelling + ADU checklist | Zoning, building and utility review |
| Attached casita or garage conversion | ADU permit | Same ADU standards as detached |
| Casita from the Model Plan Library | ADU permit, model plan | Plan review waived; site plan review $176.55 |
| Casita closer than 5 feet to a side or rear line | Design Development Option | Findings plus notice to owners within 100 feet |
| Casita in a Historic or Neighborhood Preservation Zone | Permit + historic review | District design standards apply |
| Legalizing an existing unpermitted casita | Full permit, same rules | Must meet building and zoning codes |
How much does a Tucson ADU permit cost?
A casita is new construction, so the building permit fee comes from its valuation, from the fee schedule effective July 1, 2026. The city's table values IRC dwellings at $170.80 per sq ft for wood-frame (Type VB) construction. On that value, the fee is $1,038.05 for the first $50,000 plus $9.64 per additional $1,000 to $100,000, and $1,520.05 for the first $100,000 plus $8.25 per additional $1,000 above that. Values round up. Plan review adds 50%, and the digital filing fee is 1% of the total with an $18.54 minimum.
- 400 sq ft casita: $68,320 value; $1,038.05 + 19 × $9.64 = $1,221.21; review $610.61; filing $18.54; about $1,850.
- 1,000 sq ft casita: $170,800 value; $1,520.05 + 71 × $8.25 = $2,105.80; review $1,052.90; filing $31.59; about $3,190.
- 600 sq ft model plan: $102,480 value; permit fee $1,544.80 + site plan review $176.55 + filing $18.54; about $1,740, because construction document review is waived.
On top of these, casitas pay development impact fees for parks, streets and police. The city is updating its impact fee program, so use the city's calculator for a current figure. Mechanical, electrical and plumbing work are included in the single casita building permit. You can build it yourself as an owner-builder only if you will occupy it and not rent or sell it for a year. A casita built to rent needs a licensed contractor.
How to Get a ADU Permit in Tucson
Step 1: Confirm eligibility
Check that the parcel is inside City of Tucson limits, in a zone that allows residential use, and already has a home.
Step 2: Size and site the casita
Apply the 75 percent and 1,000 square foot limits, or the 650 square foot floor, with 5-foot side and rear setbacks and the zone's height limit.
Step 3: Pick a plan
Use a pre-reviewed design from the Casita Model Plan Library or have a full plan set prepared to the ADU checklist.
Step 4: Apply and pay
File in TDC Online with the plot plan and plans. Pay the review fees up front and the permit and impact fees at issuance.
Step 5: Build, inspect and address
Get the Pima County address, pass inspections, and the approved final inspection serves as the certificate of occupancy.