A garage conversion is usually the lowest-cost path to an ADU in Phoenix — $80,000-$150,000, versus $150,000-$280,000 for a new detached build — because the shell already exists.
Garage Conversion Cost in Phoenix
Converting an existing garage in Phoenix runs $80,000-$150,000. That's well under the $150,000-$280,000 typical cost of a ground-up detached ADU, because you're reusing the foundation, walls, and roof. The biggest variables are whether the slab and framing are sound, what utility/electrical upgrades are needed, and your finish level. Permit fees add 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. A converted unit rents for about $1,150-$1,500/mo (1BR) in Phoenix.
The Phoenix Garage Conversion Permit Process
A garage-to-ADU conversion in Phoenix needs building permits even if the exterior is unchanged. Approval process: By-right building permit; a code-compliant ADU needs no public hearing, variance or use permit (ARS 9-461.18 'permitted use'; ZO 608.E.2, 706.A). Order of work: 1) confirm zoning on My Community Map and lot size and building footprints on the Maricopa County Assessor record; 2) obtain site-planning approval of a scaled plot plan showing setbacks and lot coverage; 3) submit the residential plan set through the SHAPE PHX portal or at the Residential counter, 200 W. Washington St., 2nd floor (ADU submittals are logged in for full review, not over the counter); 4) pay permit fees; 5) inspections (602-495-0800) and final. A Section 307 use permit is needed only to exceed 15 ft inside a required yard or to place a detached ADU in front of the house. Separate address on request from Addressing Services (602-256-3127); one combined water meter service is the standard 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). 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.
- Confirm eligibility — ADUs are allowed in Every residential district, on a lot with no more than one single-family detached house: S-1, S-2, RE-43, RE-24 and R1-14 (ZO Sections 603-607) and RE-35, R1-18, R1-10, R1-8, R1-6, R-2, R-3, R-3A, R-4, R-4A, R-5 and residential PADs (ZO 608.E.2, use table condition pc2). Lots with a duplex, triplex, single-family attached or multifamily units get no ADU. Look up your district on the city's My Community Map.
- Prepare conversion plans — layout, egress windows, insulation, ventilation, smoke/CO detectors, plus a kitchen and bathroom.
- Submit for 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).
- Pull permits and build — fees run 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; then framing, electrical, plumbing, and final inspection.
Parking Rules for a Garage Conversion
No additional parking may be required for an ADU (ARS 9-461.18.B.3; city ADU process guide TRT/DOC/00192 FAQ). If you convert the garage or carport, the city's ADU Beginner's Guide says the house's off-street parking must be re-established elsewhere on the lot on a dustproof surface, outside the front setback Garage conversions sometimes trigger different parking rules than new detached ADUs, so confirm replacement-parking requirements with Phoenix before you start. Owner-occupancy is not required, so you can rent the converted unit out.
The JADU Option for an Attached Garage
If your garage is attached to the house, you can convert it into a junior ADU (JADU) — capped at Phoenix has no junior ADU category. A self-contained unit carved out of the existing house (or a garage attached to it) is simply the one attached ADU allowed per lot and follows the same 75% / 1,000 sq ft limits and built within the existing walls. JADUs are cheaper and faster to permit than a full ADU, though they may share sanitation with the main home. A full ADU gives you more size and a separate unit; a JADU is the budget route.
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Phoenix Garage Conversion FAQ
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Do I need a permit to convert a garage in Phoenix?
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Compare your options: see the full Phoenix ADU rules, estimate your build with the Phoenix ADU cost calculator, or read the general garage conversion guide.