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 | $2,500-$5,000 (valuation-based) - Confirm with ABQ Planning |
| Alexandria, VA | $85,000-$190,000 | $160,000-$320,000 | ADU permit ~$75-100; building-permit fees are valuation-based |
| Anaheim, CA | $75,000-$165,000 | $130,000-$290,000 | $3,500-$12,000 |
| 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 | $90,000-$200,000 | $170,000-$340,000 | $2,800-$4,500 |
| Atlanta, GA | $60,000-$140,000 | $120,000-$240,000 | $2,400-$4,000 |
| Austin, TX | $60,000-$140,000 | $125,000-$250,000 | $2,500-$4,000 |
| Beaverton, OR | $100,000-$180,000 | $150,000-$320,000 | Type 1 application fee plus valuation-based building permit fees (third-party guides estimate $2,500-$9,000) — Confirm with Beaverton Building Division |
| Bellevue, WA | $90,000-$190,000 | $180,000-$380,000 | Permit and plan review fees based on project valuation — Confirm with Bellevue Development Services |
| Bend, OR | $70,000-$160,000 | $140,000-$280,000 | $1,700-$2,900 |
| 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 | Confirm with Dept. of Planning, Engineering & Permits |
| Boston, MA | $100,000-$220,000 | $200,000-$400,000 | $4,500-$7,500 |
| Bothell, WA | $110,000-$235,000 | $235,000-$430,000 | At submittal (2026 fees, from the city's ADU checklist): a plan check fee based on project valuation, a Single Family Planning Review fee of $231.00, and a 5 percent technology fee. At permit issuance: the permit fee, plumbing, mechanical and state fees; a Residential Site Review and Inspection fee of $834.00 where you are constructing an addition or a new building; a stormwater facility charge if you are adding square footage; and the 5 percent technology fee on everything except the state fee, impact fees and facility charges. For a new detached ADU the plumbing and mechanical permit fees are each 8 percent of the building permit fee, 16 percent in total; for a remodel or addition creating an ADU they are a base fee of $82.00 plus a per-fixture fee, most residential fixtures running $27.00 each |
| Boulder, CO | $80,000-$180,000 | $160,000-$320,000 | $1,900-$3,200 |
| Buffalo, NY | $55,000-$130,000 | $110,000-$220,000 | $2,000-$3,500 |
| Burbank, CA | $95,000-$195,000 | $220,000-$400,000 | Plan check and permit fees due at submittal — confirm current schedule with Burbank Building & Safety, (818) 238-5250 |
| Cambridge, MA | $105,000-$230,000 | $210,000-$420,000 | $3,500-$5,500 |
| Carlsbad, CA | $80,000-$180,000 | $150,000-$350,000 | Roughly $8-$15 per sq ft in combined permit/plan-check fees — Confirm with Carlsbad Building Division |
| 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 | $150,000-$300,000 | Valuation-based building-permit fees, no published flat ADU fee - third-party estimates put total Charleston ADU permitting at roughly $1,500-$3,000 |
| Charlotte, NC | $55,000-$130,000 | $115,000-$230,000 | $2,200-$3,800 |
| Chicago, IL | $80,000-$180,000 | $150,000-$300,000 | $2,800-$4,500 |
| Chula Vista, CA | $80,000-$160,000 | $300,000-$450,000 | Roughly $3-$5 per sq ft in permit/plan-check fees (local builder estimate); City Standard Plans save approximately $1,000 in plan review fees — confirm current schedule with Development Services |
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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