2026 Cost Guide
How Much Does an ADU Cost?
ADU costs range from $20,000 for a junior ADU to $350,000+ for a detached unit in a high-cost state. What you pay depends on type, location, size, and finish level. Here's the real data.
ADU Cost by Type
Junior ADU (JADU)
$20,000 – $80,000
Up to 500 sq ft
Convert existing bedroom or basement
Garage Conversion
$40,000 – $150,000
200–600 sq ft
Existing structure, lowest cost per sq ft
Attached ADU
$100,000 – $250,000
Up to 1,200 sq ft
Addition to existing home
Detached ADU
$150,000 – $350,000
Up to 1,200 sq ft
Standalone structure, most flexibility
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ADU Cost by State
| State | Detached ADU Range | Cost Per Sq Ft |
|---|---|---|
| California | $150,000 – $350,000 | $300–$520/sq ft |
| Washington | $140,000 – $300,000 | $250–$420/sq ft |
| Oregon | $130,000 – $280,000 | $220–$380/sq ft |
| Colorado | $130,000 – $280,000 | $200–$360/sq ft |
| Texas | $100,000 – $250,000 | $180–$320/sq ft |
| Florida | $110,000 – $260,000 | $190–$340/sq ft |
| Arizona | $100,000 – $230,000 | $175–$310/sq ft |
Costs reflect detached ADU construction. Garage conversions and JADUs are 40–70% less.
What's Included in ADU Cost
Construction (hard costs)
Foundation, framing, roofing, windows, exterior, rough trades
Interior Finishes
Flooring, cabinets, counters, fixtures, appliances, paint
Design & Engineering
Architect, structural engineer, energy calculations
Permits & Fees
Building permits, impact fees, utility connections
Site Work
Grading, drainage, utility trenching, landscaping repair
Contingency
Budget for unknowns — always include this
Frequently Asked Questions
How much does an ADU cost?
ADU costs vary by type and location. Detached ADUs typically cost $150,000–$350,000. Garage conversions run $40,000–$150,000. Junior ADUs (JADUs) cost $20,000–$80,000. California and Washington run 20–30% above national averages.
What is the cheapest type of ADU to build?
Junior ADUs (JADUs) are the least expensive — typically $20,000–$80,000 — because they convert existing space within your home. Garage conversions are the next most affordable at $40,000–$150,000. Detached ADUs are the most expensive.
How much does an ADU cost in California?
California ADU costs typically range from $150,000–$350,000 for a detached unit. Garage conversions run $75,000–$175,000. The Bay Area and Los Angeles run 20–30% higher than the state average.
What affects ADU cost the most?
The biggest cost drivers are: ADU type (detached vs garage conversion vs JADU), location (labor costs vary by state), size (cost per sq ft decreases as size increases), finish level (standard vs premium materials), and site conditions (slope, utilities, soil).
Next Steps
Cost data is based on contractor surveys and published ADU cost studies as of early 2026. Actual costs vary by project scope, site conditions, and local labor markets. Always get multiple contractor bids before budgeting.