Garage Conversion Cost (2026): ADU, Living Space, and Studio Pricing
By Fabio Freire, Founder & General Contractor at EZ-Estimates. Published 2026-07-17.
Garage Conversion Cost (2026): ADU, Living Space, and Studio Pricing
Homeowner texts a photo of their 2-car garage and asks "how much to turn this into an ADU". If you shoot a number back without walking the site, you are guessing on ceiling height, slab condition, code egress, plumbing runs, and 15 other variables that swing the price by $40,000 in either direction.
Garage conversions look easy from the outside. They are not. The shell exists but almost nothing behind the drywall is code-compliant for habitable space. Insulation is thin. HVAC does not extend. Electrical is a single 20-amp circuit for a garage door opener. Plumbing usually is not there at all. Getting a garage rebuilt to residential code is 70% of a ground-up build in cost.
Here is what garage conversions really cost in 2026.
Garage Conversion Cost Per Sq Ft (2026 Ranges)
Installed cost per finished square foot for a standard 400 to 600 sqft attached or detached garage conversion.
| Conversion Type |
Low End |
Mid Range |
High End |
| Basic Living Space (no plumbing) |
$50/sqft |
$75/sqft |
$100/sqft |
| Studio with Bath |
$75/sqft |
$110/sqft |
$145/sqft |
| Full ADU with Kitchen + Bath |
$90/sqft |
$130/sqft |
$200/sqft |
| Home Gym or Office (no bath) |
$45/sqft |
$65/sqft |
$85/sqft |
| Rental ADU (permitted, all in) |
$100/sqft |
$150/sqft |
$220/sqft |
For a standard 480 sqft garage:
- Home office / gym: $21,600 to $40,800
- Living space (no plumbing): $24,000 to $48,000
- Studio with bath: $36,000 to $70,000
- Full ADU: $43,000 to $96,000
- Permitted rental ADU (Cal, WA, Colorado): $48,000 to $105,600
What Actually Has to Be Done
A garage conversion is a code upgrade project. Even if the shell looks solid, the following almost always need addressing:
Slab. Most garages slope 1/4 inch per foot toward the door for drainage. That is not code for habitable space. You need to either self-level the floor ($4 to $8/sqft), pour a new slab on top ($8 to $14/sqft), or build a raised subfloor system ($6 to $12/sqft).
Walls. Garage walls are usually R-11 batts (or nothing). Habitable code requires R-19 to R-21 minimum in walls, R-38 to R-49 in ceilings depending on climate zone. Re-insulation costs $2.50 to $5/sqft of wall/ceiling.
Windows and egress. Code requires natural light (typically 8% of floor area) and egress (bedroom needs a 5.7 sqft opening). Adding a proper egress window is $2,500 to $6,500 including framing, header, and finishing.
Garage door removal. The door has to go. Frame in the opening, add proper sheathing, insulate, drywall, and finish exterior. That is $4,500 to $9,500.
HVAC. Existing furnace or heat pump might not have capacity for 400+ more sqft. Options: extend existing (ductwork run + return + register, $2,500 to $5,500), add a ductless mini-split ($4,500 to $7,500), or supplement with a heat pump (variable).
Electrical. A garage typically has 1 to 2 circuits. Living space needs at least 4 to 6 circuits for lighting, receptacles, HVAC, kitchen (if ADU). Panel might need upgrade to 200A. Electrical scope: $4,500 to $12,000+.
Plumbing (for bath or kitchen). Requires connecting to main house drain and water supply. Slab has to be cut to bury waste and vent lines. Slab cut and re-pour is $2,500 to $6,000 per bath. Full plumbing rough-in is $8,000 to $18,000.
Ceiling height. Habitable space requires 7 ft minimum in most jurisdictions. If the garage ceiling is 8 ft, drywall + finish drops to about 7.75 ft. Fine. If it is 7.5 ft joist to slab, you may be tight after finish.
Fire separation. Attached garages have a 5/8 fire-rated drywall assembly between the garage and house. When converting, that wall must be brought into the house envelope with proper insulation and finish.
Home Office / Gym Conversion Breakdown
Simplest scope. No plumbing. Just insulation, drywall, floor, HVAC, and finish.
Sample estimate for a 400 sqft home office conversion:
| Line Item |
Cost |
| Slab prep and self-level |
$2,400 |
| Frame in garage door opening |
$3,800 |
| Batt insulation (R-19 walls, R-38 ceiling) |
$2,200 |
| Drywall + finish |
$4,800 |
| Interior paint |
$1,600 |
| LVP flooring |
$3,200 |
| Ductless mini-split (12k BTU) |
$4,800 |
| Electrical (4 new circuits, panel work) |
$3,500 |
| 3 new windows + egress |
$4,500 |
| Interior door + trim |
$1,200 |
| Baseboards + trim |
$1,400 |
| Permit and inspection |
$600 |
| Materials/Sub Subtotal |
$34,000 |
| GC overhead (12%) |
$4,080 |
| GC profit (15%) |
$5,712 |
| Total Estimate |
$43,792 |
That works out to about $109/sqft. Middle of range.
Full ADU with Kitchen and Bath Breakdown
Complete rental-ready ADU. Kitchen, full bath, sleeping area, HVAC, all utilities.
Sample estimate for a 480 sqft attached garage ADU conversion:
| Line Item |
Cost |
| Slab prep, cut for plumbing, re-pour |
$6,500 |
| Frame in garage door opening (structural insulated) |
$5,200 |
| Rough framing (partition walls, ceiling if needed) |
$3,800 |
| Rough plumbing (bath + kitchen, connect to main) |
$12,500 |
| Rough electrical (200A subpanel + circuits) |
$8,800 |
| HVAC (ductless multi-zone) |
$8,500 |
| Insulation (R-21 walls, R-49 ceiling, R-30 floor if raised) |
$4,200 |
| Windows (2 new + egress) |
$5,800 |
| Exterior door |
$1,500 |
| Drywall + finish |
$6,800 |
| Interior doors and trim |
$2,400 |
| Kitchen (basic cabinets, quartz counter, sink, appliances) |
$12,500 |
| Bathroom (full, tile shower, vanity, toilet, exhaust) |
$9,500 |
| Flooring (LVP throughout) |
$3,800 |
| Paint |
$2,200 |
| Light fixtures and hardware |
$2,400 |
| Water heater (tankless) |
$2,800 |
| Permit and inspection (ADU) |
$2,500 |
| Materials/Sub Subtotal |
$101,700 |
| GC overhead (12%) |
$12,204 |
| GC profit (14%) |
$15,948 |
| Total Estimate |
$129,852 |
That is $270/sqft for a fully permitted, rentable ADU. Solid mid-range number.
Permits and Legal Considerations
Permitted ADU vs unpermitted conversion. A homeowner who converts their garage without permits is creating a code issue that follows the property. Buyer inspections will flag it. Insurance may not cover damage. Rentability is limited.
Bid for permitted work every time. If the client insists on unpermitted work to save money, walk. It is not worth your license.
ADU zoning. Not every jurisdiction allows attached or detached ADUs. California (AB 68/881), Oregon, Washington, Colorado, Vermont, and Utah are ADU-friendly. Most Texas, Florida, and Georgia jurisdictions still restrict them. Check zoning before bidding.
Separate utility meters. Some jurisdictions require a separate electric meter for a rentable ADU. Adds $2,500 to $5,000 to electrical scope.
Fire sprinklers. In California and some Oregon jurisdictions, ADUs may trigger fire sprinkler requirements for the main house. Adds $8,000 to $22,000. Verify before quoting.
Parking. Some cities require a replacement parking space when a garage is converted. Concrete parking pad runs $4,500 to $9,500.
Regional Cost Multipliers
- California (LA, SF, San Diego): +40% to +80%. Highest ADU volume in the country. Labor and permit fees are brutal.
- Pacific Northwest (Seattle, Portland): +25% to +40%. High labor cost, strict energy code.
- Northeast (Boston, NYC, DC): +30% to +50%. Older housing stock, strict code, high labor.
- Sunbelt (Phoenix, Austin, Dallas): Baseline. Growing ADU market.
- Midwest, Southeast secondary: Baseline to -10%.
Contractors in Los Angeles, San Francisco, and San Diego are running near-continuous ADU pipelines. Contractors in Denver and Portland have seen ADU activity double since 2023.
Common Garage Conversion Estimating Mistakes
Assuming the slab is level and dry. It never is. Test moisture and slope before quoting. Water intrusion at the door seam is standard.
Missing the panel upgrade. Adding an ADU almost always requires 200A service. Panel upgrade is $2,500 to $6,500. Include it or eat it.
Under-quoting the plumbing tie-in. Sewer connection to the main house drain is often 30 to 60 feet away. Trenching, PVC, and re-connection can be $4,500 to $10,000 just for the outside work.
Forgetting exterior finish. Filling in the garage door opening leaves a big patch. Matching existing siding, stucco, or brick is $3,500 to $8,000 in exterior work.
Not budgeting for HVAC extension. "Just tie it into the existing system" is usually not possible. Existing air handler will not have the tonnage.
Related Reading
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