Everything homeowners ask about building an ADU in Tucson — answered with 2026 data.
Yes, ADUs are allowed in Any parcel in a zone that permits residential use and is developed with a Family Dwelling (single-family detached or attached, manufactured home, duplex); UDC 6.6.3.B. Multifamily developments (3+ units on one lot) are excluded, and Middle Housing (2-4 unit buildings) is defined separately from ADUs (UDC 11.3.7.A.3). Casitas are allowed inside Historic Preservation Zones, Historic Landmark and Neighborhood Preservation Zones but must pass that district's design review (6.6.3.B.8). State law does not reach tribal land or land in the noise territory of an airport (A.R.S. 9-461.18(G)). Check your zone with the city's zoning map or PDSD at (520) 791-5550 in Tucson, AZ. The maximum size for a detached ADU is 75% of the gross floor area of the principal dwelling, not to exceed 1,000 sq ft of gross floor area; a casita may always be up to 650 sq ft regardless of the size of the main house (UDC 6.6.3.B.5). Gross floor area means interior habitable area (A.R.S. 9-461.18(I)(2)). Lot coverage in R-1, R-2 and R-3 is capped at 70% for single-family use (Table 6.3-2.A), and ADUs are exempt from the zone's maximum residential density (6.6.3.B.1). Attached ADUs can be up to Same cap as detached: 75% of the main house up to 1,000 sq ft, with 650 sq ft always allowed. Tucson has an ADU-friendliness score of 7/10. Check our full Tucson ADU rules page for complete zoning details.
ADU construction in Tucson typically costs $150,000-$250,000. The cost per square foot averages $150-$300. Garage conversions are more affordable at $60,000-$150,000, while prefab ADUs cost $150-$300 per sq ft. Permit fees add City fees are valuation-based (FY2027 Planning and Permitting Fee Schedule, effective July 1, 2026). Building permit for new construction: $1,038.05 plus $9.64 per $1,000 over $50,000, or $1,520.05 plus $8.25 per $1,000 over $100,000 (Section 4-02.4); building staff review (plan check) for residential is 50% of the permit fee (4-02.2.1); digital filing fee 1% (minimum $18.54). Worked example: a $120,000 valuation gives a $1,685.05 permit + $842.53 plan review + about $25 filing = roughly $2,550; at $200,000 it is about $3,550. Using an approved model plan waives the construction-document review and substitutes a $176.55 site-plan review (4-02.3.3), so the same $120,000 casita pays about $1,880. Valuation follows the ICC Building Valuation Data table; ask PDSD (pdsdinquiries@tucsonaz.gov) for the current per-square-foot figure. Setback relief via the Design Development Option costs $278.07 plus public-notice fees to your budget. See our detailed Tucson ADU cost guide.
Detached ADUs in Tucson can be up to 75% of the gross floor area of the principal dwelling, not to exceed 1,000 sq ft of gross floor area; a casita may always be up to 650 sq ft regardless of the size of the main house. Attached ADUs are limited to Same cap as detached: 75% of the main house up to 1,000 sq ft, with 650 sq ft always allowed. Junior ADUs (JADUs) have a cap of Tucson has no junior ADU category. A unit inside the house counts as one of the two ADUs allowed per lot and follows the same 75% / 1,000 sq ft cap; a garage or carport built on a property line can only become a casita if it meets the 5-ft setback or wins relief through the Design Development Option (UDC 3.11.1, $278.07 staff review fee plus public notice, with neighbors within 100 ft notified). Maximum height is Same as a single-family home in the zone (UDC 6.6.3.B.7 and 6.6.3.D): 25 ft in R-1, R-2, R-3, RX-2, MH-1 and MH-2; 30 ft in RH, SR, SH and RX-1 (Tables 6.3-1.A and 6.3-2.A). State law bars the city from setting a lower height for ADUs than for houses in the same zone (A.R.S. 9-461.18(B)(5)). Ordinary sheds and other accessory structures are held to 12 ft, but that limit does not apply to ADUs. You are allowed up to Two ADUs per parcel developed with a Family Dwelling; one ADU on a parcel developed with a duplex on a qualifying lot.
Rear setback: 5 ft minimum from the rear property line (UDC 6.6.3.B.6), the ceiling allowed by A.R.S. 9-461.18(B)(6). Chimneys, roof overhangs and bay windows may project 2 ft into the yard as long as 3 ft remains (6.4.5.D.1). A casita cannot be built over a public utility easement without the utility's written consent (A.R.S. 9-461.18(E)). Side setback: 5 ft minimum from each interior side property line (UDC 6.6.3.B.6); 10 ft from a side street property line on a corner lot (6.4.5.C.1.b). Same 2-ft eave/chimney projection allowance as the rear yard. Front setback: A detached casita is not permitted in the area between the house and the front street lot line, i.e. it must sit behind the front wall of the house; only shade structures or carports up to 400 sq ft, low terraces, paving and walls may go there (UDC 6.6.3.C). An attached ADU follows the house's 20-ft front street perimeter yard (6.4.5.C.1.a); lots in approved subdivisions may have a 5-ft front yard shown on the plat. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None. Vehicular parking is not required for an ADU (UDC 6.6.3.B.3) and the city may not demand added parking or an in-lieu fee (A.R.S. 9-461.18(B)(3)). No replacement parking is required if a garage or carport is converted, but a converted structure must still meet setbacks and building code. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required for long-term rental. The UDC contains no owner-occupancy rule for ADUs, and A.R.S. 9-461.18(B)(1)-(2) bar the city from prohibiting separate long-term leasing (90 days or more, or month to month) of the house or the casita or from requiring a family or employment relationship between the occupants. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Tucson is typically PDSD's published performance goal is 10 business days per review cycle for the 'Residential ADU / Casita' and 'Residential Model from Template' permit types (Fast Lane), after up to 3 business days for intake; residential additions/alterations run in the 20-business-day Standard Lane. Corrections restart the clock, so plan on one to three months from a complete application to a permit, and 4-8 months of construction. Arizona has no deemed-approved deadline for ADU permits. Plan check: Electronic review through the TDC portal; all disciplines (zoning, building, MEP, energy, fire) review the one submittal. Review fee is 50% of the building permit fee (waived for an unmodified model plan). Plans must show the 2024 IECC thermal envelope, Manual J/S/D HVAC sizing (REScheck accepted for energy), a plumbing fixture-unit and water-supply calculation covering both buildings when a meter is shared, a complete panel schedule and riser diagram, Outdoor Lighting Code fixture data, egress windows in every bedroom (5.7 sq ft clear, 24 in. high, 20 in. wide, sill no higher than 44 in.) and at least one 36-in. exterior door. An engineer is required for engineered trusses and other conditions in PDSD's truss policy. State law bars the city from requiring fire sprinklers or the commercial code for an ADU (A.R.S. 9-461.18(D)). Pre-approved plans availability: Yes. The city's Casita Model Plan Library (casitas.tucsonaz.gov) listed 11 pre-approved designs in September 2026: 6 design-competition winners and 5 other approved plans, together offering about 20 floor-plan options from a 156 sq ft studio to a 1,000 sq ft two-bedroom, two-bath unit. Plans are licensed from their designers for a one-time fee set by the designer (not paid to the city); the license does not transfer ownership, and any change to the plan sends it back through full review. You still submit a site plan showing utility routes and pay the building permit and impact fees, but the construction-document review fee is waived and the permit runs in the Fast Lane. Model plans are valid for one year and renewable until the residential code changes; Arizona-certified modular designs can also be added to the library.
Average ADU rental income in Tucson: 1-bedroom units rent for $950-$1,300/month, 2-bedroom units for $1,200-$1,700/month. Short-term rentals: Yes, with a city business license and transient (bed) tax. A.R.S. Expected ROI: 5-8% gross rental yield on a $150,000-$250,000 detached casita renting at $950-$1,300/mo (estimate before taxes, vacancy, financing and the $3,515-$5,420 impact fee).
The minimum lot size for an ADU in Tucson is No ADU-specific minimum: a casita is allowed on any lot that lawfully holds a single-family home, and the city may not set a stricter lot-size, coverage or frontage rule for ADUs than for houses (A.R.S. 9-461.18(B)(5)). For reference, the zone minimums after Ordinance 12219 are 6,000 sq ft in R-1 and 4,000 sq ft in R-2 and R-3 (Table 6.3-2.A); a casita cannot be sold separately unless the lot is legally split into two lots that each meet that minimum. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Tucson, a garage conversion typically costs $60,000-$150,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
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