Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Phoenix ADU cost →Building an ADU in Phoenix costs between $150,000-$280,000 for new construction, with per-square-foot costs averaging $200-$350. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $80,000-$150,000, while prefab/modular ADUs fall in between at $155,000-$300,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | Valuation-based (PDD Fee Schedule, Ordinance G-7465, effective January 20, 2026, Table A): permit fee $703 on the first $50,000 plus $9 per $1,000 up to $200,000, then $2,053 plus $9 per $1,000; residential plan review is 80% of the permit fee when valuation exceeds $50,000 (100%, minimum $195, at or below); plot plan review $98; each extra utility meter $98. Examples: a $150,000 valuation is about $1,603 permit + $1,282 plan review + $98 = $2,983; $250,000 is about $2,503 + $2,002 + $98 = $4,603. Valuation is the higher of the city's square-foot valuation table or your contract price. Re-inspections after the first are $195 each |
| Impact Fees | Depends on where the lot is. Under the Development Impact Fee schedule effective June 23, 2025, the established city ('Balance of City') pays no fire, police, parks, library, arterial or storm-drain impact fees; the growth-area zones (Northwest, Deer Valley, Northeast, Paradise Ridge, Estrella, Laveen, Ahwatukee) charge a single-family dwelling roughly $12,000-$35,000 in total. Citywide the schedule lists per-dwelling water treatment ($4,387), wastewater treatment ($1,071) and water resource acquisition ($2,009, off-project) fees for a single-family unit on a meter up to 1 in. The schedule does not say whether an ADU on the house's existing meter is assessed, so email impactfees@phoenix.gov with your APN before budgeting; a 1% administrative charge applies to any gross fee |
| Site Prep & Foundation | $10,000 – $35,000 |
| Framing & Structure | $15,000 – $45,000 |
| Plumbing | $8,000 – $20,000 |
| Electrical | $5,000 – $15,000 |
| HVAC | $3,000 – $8,000 |
| Interior Finishes | $15,000 – $40,000 |
Quotes for the same ADU commonly vary 20–40% between builders. We pass your request to up to 5 local builders serving Phoenix, where we have them — free, no obligation.
Get Phoenix builder quotes →Permit fees in Phoenix are Valuation-based (PDD Fee Schedule, Ordinance G-7465, effective January 20, 2026, Table A): permit fee $703 on the first $50,000 plus $9 per $1,000 up to $200,000, then $2,053 plus $9 per $1,000; residential plan review is 80% of the permit fee when valuation exceeds $50,000 (100%, minimum $195, at or below); plot plan review $98; each extra utility meter $98. Examples: a $150,000 valuation is about $1,603 permit + $1,282 plan review + $98 = $2,983; $250,000 is about $2,503 + $2,002 + $98 = $4,603. Valuation is the higher of the city's square-foot valuation table or your contract price. Re-inspections after the first are $195 each. The review timeline is Not published as a fixed ADU figure. Planning & Development posts a monthly Plan Review Turnaround Times report (goal vs. actual, by plan type) on its Reports, Data and Turnaround Times page; plan on at least one correction cycle. Phoenix builders' 2026 guides quote 6-12 months from design start to move-in for a detached casita and 4-6 months for a garage conversion, with plan check: Full residential plan review (no over-the-counter path for ADUs). Submit a plot plan with site-planning approval, floor plans, elevations, structural and energy-code documents per the Residential Plan Submittal Checklist, and note fire-rating requirements per IRC R302; no grading-and-drainage plan is required for an attached or detached ADU (TRT/DOC/00192). Extra reviews apply on hillside lots (slope over 1:10), historic properties and floodplain lots. State law bars the city from requiring a fire sprinkler or commercial-code compliance in an ADU (ARS 9-461.18.D). Impact fees are Depends on where the lot is. Under the Development Impact Fee schedule effective June 23, 2025, the established city ('Balance of City') pays no fire, police, parks, library, arterial or storm-drain impact fees; the growth-area zones (Northwest, Deer Valley, Northeast, Paradise Ridge, Estrella, Laveen, Ahwatukee) charge a single-family dwelling roughly $12,000-$35,000 in total. Citywide the schedule lists per-dwelling water treatment ($4,387), wastewater treatment ($1,071) and water resource acquisition ($2,009, off-project) fees for a single-family unit on a meter up to 1 in. The schedule does not say whether an ADU on the house's existing meter is assessed, so email impactfees@phoenix.gov with your APN before budgeting; a 1% administrative charge applies to any gross fee. Pre-approved plans: In progress. The city's ADU Standard Plan Library, built from the 2024 City of Phoenix / AIA Phoenix Metro design competition, listed four detached designs marked 'in review' on the city ADU page in May 2026; approved plans are free to Phoenix residents, must be used without modification and still need a plot/site plan. State law (ARS 9-461.20, from SB 1529 of 2025) requires Phoenix to offer at least three pre-approved ADU plans at 200, 600 and 1,000 sq ft from July 1, 2026 and to accept outside plan submissions; check the city ADU page for the current list.
| 1-Bedroom Rent | $1,150-$1,500/month |
| 2-Bedroom Rent | $1,500-$1,750/month |
| Annual Rental Income (est.) | $15,900/year |
| Payback Period (est.) | 13.5 years |
| Short-Term Rental | Yes, with a city short-term rental permit for each unit (City Code Ch. 10 Art. XVI; TPT license, $500,000 liability insurance, neighbor notice). |
| Overall ROI Estimate | Roughly 6-11% gross rental yield on a $150,000-$280,000 detached build at $1,300-$1,700/mo (before taxes, vacancy, insurance and financing) |
A typical ADU in Phoenix generates approximately $15,900 per year in rental income based on average 1-bedroom rents. At an average construction cost of $215,000, the estimated payback period is 13.5 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Phoenix and varies by market (often less than build cost).
1. Garage conversions save 40-60% vs new construction since the shell already exists. Average cost in Phoenix: $80,000-$150,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $155,000-$300,000.
3. Pre-approved plans — available in Phoenix, which can save $3,000-$10,000 in design costs and 2-3 months in review time. See which cities offer pre-approved ADU plans.
4. State grants — California's CalHFA ADU grant (up to $40K) is currently paused; check calhfa.ca.gov/adu for status and your state for active programs.
5. Get multiple bids — ADU contractor pricing varies 20-40% for the same project. We recommend getting at least 3 quotes.
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