A garage conversion turns space you already own into a legal dwelling. Because the shell is standing, it typically costs less than half of a comparable new detached ADU. The trade-offs are that you lose the garage, you are limited to its existing footprint, and older slabs and walls sometimes need work the estimate did not anticipate.
The parking question decides many projects
In California, cities may not require you to replace the parking space when a garage is converted to an ADU (AB 68, Gov. Code §66314) — 38 of the California cities on this site are covered by that rule. Outside California there is no single answer: some cities require a replacement space somewhere on the lot, which can make an otherwise cheap conversion impossible on a narrow parcel. Check your own city below before you budget anything.
What a garage conversion costs
These are published local figures, not a national average. The spread between cities is wider than most guides admit, and it is mostly labour and permit cost, not materials.
| City | Garage conversion | New detached ADU | Permit fees |
|---|---|---|---|
| Albuquerque, NM | $60,000-$130,000 | $120,000-$240,000 | Valuation-based (Plan Review and Building Permit Fees table, rev. April 2010, still posted): a $150,000-$250,000 casita pays about $640-$920 permit plus $415-$600 plan review (65%), $25 zoning, $50 hydrology and trade permits. Site Plan - Administrative fee: see the Planning General Fee Schedule. |
| Alexandria, VA | $80,000-$150,000 | $150,000-$350,000 | No separate ADU permit since June 2025 (a $135 ADU zoning-permit line remains in the FY2027 P&Z schedule; confirm). Building permit: new construction $0.75/sq ft plus $194 each electrical, plumbing, mechanical; alterations $0.30/sq ft ($95 min); plus 5% tech fee and state levy (FY26 schedule). |
| Anaheim, CA | $90,000-$200,000 | $220,000-$450,000 | Building Permit Fees schedule (Exhibit A, Tier 3 Type VB, Residential Category 1, Dwellings and Custom; posted Aug 2026): combined plan check and building permit of $1,677 for the first 500 sq ft plus $213 per extra 100 sq ft up to 1,000 sq ft (about $2,316 for an 800 sq ft ADU), then $2,741 at 1,001 sq ft plus $171 per 100 sq ft (about $3,083 for 1,200 sq ft). Add trade permits (electrical $26 for the first 100 sq ft plus $0.26 per sq ft; plumbing $49 per fixture; $188 minimum per trade permit), Zoning Plan Check $352 and a $114 address fee (Planning fee schedule, Aug 2025). Budget roughly $3,000-$4,500 in city fees for an 800-1,200 sq ft detached ADU before impact and school fees |
| Ann Arbor, MI | $60,000-$130,000 | $120,000-$240,000 | Building and trade permit fees are based on construction valuation — confirm current fee schedule with the Ann Arbor Building Department |
| Arlington, VA | $80,000-$160,000 | $150,000-$350,000 | AD Permit $582 plus $387 if a DES parking survey is needed (FY2027 Planning and Zoning fee schedule, effective July 1, 2026). Building permit $1.70 per sq ft for new construction/additions or $0.63 per sq ft for alterations, plus a 2% state levy and a 10% automation surcharge; CO for an AD $520. |
| Atlanta, GA | $60,000-$140,000 | $120,000-$240,000 | $1,700-$2,750 for a $150,000-$300,000 ADU: building permit $7 per $1,000 of construction cost (minimum $150) plus a $25 technology fee, three trade permits at $150 plus $25 each, and a $100 certificate of occupancy (Department of City Planning fee tables, checked Sept 2026). |
| Austin, TX | $30,000-$100,000 | $150,000-$350,000 | About $1,850-$2,150 in DSD fees for an 800-1,200 sq ft unit (FY2025-26 residential schedule, eff. Oct 1, 2025): $106.72 processing + $896.50-$1,220 plan review + roughly $840-$885 in building, electrical, mechanical, plumbing and energy permits; Austin Energy adds $220-$440. |
| Avondale, AZ | $80,000-$150,000 | $150,000-$280,000 | FY2027 schedule (eff. 9/1/2026): permit $1,247 + $8 per $1,000 of valuation over $100,000, plan review 65% of that, $102 application fee, $158 C of O — about $2,400 for a 600 sq ft casita valued near $106,000 and $3,320 at 1,000 sq ft (~$176,000). Impact fees are separate |
| Beaverton, OR | $70,000-$160,000 | $165,000-$300,000 | The ADU land-use fee is set in the Citywide Comprehensive Fee Schedule (Exhibit A to the fee resolution) and the building permit is valuation-based (Building Permit Fee Schedule B70-1108); both PDFs were behind a bot check on 9/20/2026, so confirm current figures with Community Development. |
| Bellevue, WA | $100,000-$225,000 | $325,000-$550,000 | Fees are set by the 2026 fee ordinance (Ord. 6879): a plan-review deposit at submittal and an inspection deposit at issuance, charged at the stated hourly rate with monthly invoices for overage. Use the City's Permit Fee Estimator (permitfeeestimator.bellevuewa.gov) for a figure |
| Bend, OR | $60,000-$150,000 | $225,000-$350,000 | Roughly $3,000-$4,000 for a 600-800 sq ft ADU at FY2025-26 rates: building permit $1,212.58 for the first $100,000 of valuation + $7.00 per extra $1,000, plan review 65%, 12% state surcharge, 0.33% affordable-housing fee, plus trade permits. The City emails project estimates. |
| Berkeley, CA | $120,000-$250,000 | $250,000-$500,000 | $250 zoning plan check + $500 neighbor noticing fee at submittal + $250 address assignment; building permit fees based on project valuation (city fee estimator tool available) |
| Birmingham, AL | $40,000-$95,000 | $90,000-$180,000 | Building permit $9.50 per $1,000 of valuation, $125 minimum, plus a $150 Certificate of Occupancy (2024 Technical Code, Art. V); trades covered under the general contractor pay a processing fee only. A $120,000 ADU is about $1,140 plus the CO. |
| Boston, MA | $150,000-$275,000 | $75,000-$350,000 | Long-form building permit $50 plus $10 per $1,000 of estimated construction cost (ISD fee schedule dated May 15, 2023): about $950 on a $90,000 interior ADU, $3,050 on a $300,000 detached ADU; ZBA appeal $150 for a 1-3 family home. |
| Bothell, WA | $100,000-$225,000 | $325,000-$550,000 | 2026 fees: a valuation-based permit fee (Table 20.02.155-A: $1,514 plus $9 per $1,000 over $100,000), plan check at 65 percent, planning review $231, site review $834, energy review $230, plumbing and mechanical 16 percent, 5 percent tech fee. A $300,000 detached ADU: about $7,700 plus impact fees |
| Boulder, CO | $100,000-$250,000 | $200,000-$450,000 | Valuation-based (2026 schedule): $1,059 + $5.95 per $1,000 over $100,000, plus 25% plan check and $83.90 energy fee: about $1,700 for an 800 sq ft unit at the city's $170.80/sq ft floor, about $2,900 on a $300,000 contract. Use tax, trade permits, impact fees and excise tax are extra. |
| Buckeye, AZ | $80,000-$150,000 | $150,000-$280,000 | $4,100-$5,600 in permit and plan-review fees for a 600-1,000 sq ft casita (Development User Fee Schedule, Res. 38-26, effective May 21, 2026: Table 1-A permit fee on the ICC valuation of $175.92/sq ft, plus 65% plan review and a $54 plot-plan review) |
| Buffalo, NY | $55,000-$130,000 | $110,000-$220,000 | Building-permit fees are set on construction value; the current schedule was not retrievable online - confirm with Permit & Inspection Services. Zoning fees (OSP memo eff. July 1, 2025): area variance $150 (1-2 units), minor site plan $350, special use permit $350. |
| Burbank, CA | $100,000-$225,000 | $220,000-$400,000 | Planning ADU application fee $1,728.42 (FY2026-27 Planning Fees, effective July 1, 2026); building plan check and permit fees are valuation-based under the Citywide Fee Schedule (confirm with Building & Safety, (818) 238-5220). BWP water charges run 'from a few hundred up to ten thousand dollars' depending on fixture count, main location and any new service, paid before Water Division approval; BWP electric aid-in-construction fees and a kVA capacity charge apply to any new, upgraded or relocated panel (since Oct 1, 2023). A school district facilities receipt is required at submittal |
| Cambridge, MA | $100,000-$250,000 | $220,000-$400,000 | Building permit $15 per $1,000 of construction cost for buildings of 3 dwelling units or fewer ($20 per $1,000 otherwise), $50 minimum (ISD Building Fees table): about $3,750 on a $250,000 ADU, $5,250 on $350,000. Plan review included; certificate of occupancy $100; trade permits extra. |
| Carlsbad, CA | $80,000-$200,000 | $300,000-$450,000 | About $2,800-$3,000 permit plus plan check for a 750-1,200 sq ft ADU: R-3 base fee $1,700 up to 1,000 sq ft plus $0.35 per extra sq ft, plan check 65% of the permit (FY 2026-27 Master Fee Schedule, eff. Sept. 1, 2026); the city's ADU page says $2,000-$4,000. Coastal Zone detached: $3,974 minor CDP. |
| Chandler, AZ | $60,000-$140,000 | $125,000-$250,000 | Valuation-based per Chandler fee schedule using ICC Building Valuation Data (minimum permit fee $60); third-party guides estimate roughly 1.5-2% of construction value plus plan review — confirm exact amounts with Chandler Development Services |
| Charleston, SC | $60,000-$150,000 | $140,000-$300,000 | Valuation-based (fee schedule eff. Oct. 1, 2019): $40 application + permit fee ($260 + $4 per $1,000 over $50,000; $460 + $3 per $1,000 over $100,000) + plan review at 50% of the permit fee. An 850 sq ft ADU at the schedule's $116.15/sq ft is about $724 before trade permits; budget $700-$1,300. |
| Charlotte, NC | $55,000-$130,000 | $115,000-$230,000 | $900-$1,700 county building permit for a $100,000-$250,000 ADU (LUESA Fee Ordinance rev. July 1, 2026, Sec. II.A.1: $632.57 + $5.49 per $1,000 over $50,000, $907.12 + $5.93 per $1,000 over $100,000, $1,203.52 + $4.59 per $1,000 over $150,000) plus a $3 technology charge and the city LDIRL fee. |
Figures are the ranges published on each city’s own page and are updated when the underlying rules change. They are estimates for planning, not quotes — a builder pricing your actual slab, ceiling height and electrical service is the only number that binds.
Where the rules differ
Three things vary enough to change the answer for your lot:
- Replacement parking. Barred in California. Elsewhere it is the single most common reason a garage conversion does not pencil.
- Ceiling height and egress. A garage built to store a car is not built to be slept in. Expect to raise the floor, add a window, or both.
- Setbacks for the existing structure. Many garages sit closer to the property line than a new ADU would be allowed. Most codes let an existing lawful structure keep its position when converted — but not all, and that is worth confirming before you draw anything.
Garage conversion rules by city
Each page below covers that city’s own cost range, parking rule, permit path and size limits.
Every city we cover → · Los Angeles garage conversions in depth →
Common questions
Is converting a garage cheaper than building a new ADU?
Almost always, because the foundation, walls and roof already exist. Across the cities on this site the conversion range typically runs well under half the new-build range. It stops being cheaper when the slab, ceiling height or electrical service has to be rebuilt anyway.
Do I have to replace the parking space?
In California, no — state law bars cities from requiring it. Outside California it depends entirely on your city, and it is the first thing to check.
Can I convert a detached garage as well as an attached one?
Yes, and a detached garage often converts more easily: it is already a separate structure, so it raises fewer questions about fire separation and shared walls.
Will a converted garage count as a JADU or a full ADU?
Usually a full ADU, because a JADU must be created within the walls of the existing house. A garage attached to the house can sometimes qualify as a JADU where the local code allows it, which can mean lower fees. Your city page says which applies.
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