ADU Construction Cost in 2026
Real ADU construction cost ranges from $150,000 to $500,000 all-in across major US metros in 2026. Below: per-city pricing, the full cost breakdown line-by-line, and the five proven ways to lower your build cost.
National median ADU build
Per sq ft (varies by metro)
Avg home value lift (NAR 2025)
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ADU Construction Cost by City (2026)
All-in build cost ranges for a typical 700–1,000 sq ft detached ADU in 11 major metros. Includes design, permits, sitework, and finishes. Excludes land cost.
| City | Low estimate | High estimate | Full guide |
|---|---|---|---|
| San Francisco | $350,000 | $600,000 | Read cost guide |
| Los Angeles | $300,000 | $550,000 | Read cost guide |
| San Diego | $270,000 | $500,000 | Read cost guide |
| Seattle | $250,000 | $450,000 | Read cost guide |
| Miami | $240,000 | $420,000 | Read cost guide |
| Scottsdale | $230,000 | $410,000 | Read cost guide |
| Denver | $220,000 | $400,000 | Read cost guide |
| Sacramento | $210,000 | $380,000 | Read cost guide |
| Portland | $200,000 | $370,000 | Read cost guide |
| Austin | $190,000 | $350,000 | Read cost guide |
| Raleigh | $170,000 | $320,000 | Read cost guide |
ADU Construction Cost Breakdown (where every dollar goes)
A $260K national-median ADU build breaks down like this. Use these percentages to sanity-check any builder quote — anything outside these bands deserves a follow-up question.
| Category | % of total | What's included |
|---|---|---|
| Design & architecture | 8–12% | Permit drawings, structural engineering, T24 energy calcs |
| Permits & city fees | 2–10% | Building, water/sewer hookup, school fees (some cities waive) |
| Sitework & utilities | 8–15% | Grading, foundation prep, gas/electric/water/sewer trenching |
| Framing & shell | 20–25% | Foundation, framing, roof, siding, windows, doors |
| MEP rough-in | 12–18% | Plumbing, electrical, HVAC rough installation |
| Interior finishes | 15–20% | Drywall, flooring, cabinets, counters, fixtures, paint |
| Kitchen & bath | 10–15% | Per-unit fixtures, appliances, tile |
| Soft costs & buffer | 10–15% | Insurance, financing fees, 10% contingency reserve |
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Cost calculator
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Cost by size
400 sq ft to 2,000 sq ft pricing across 16 metros (144 pages).
Financing options
HELOC vs cash-out refi vs construction loan with 2026 rates.
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Vetted ADU builders by city with verified pricing.
ADU Construction Cost FAQ
What is the average ADU construction cost in 2026?
A typical detached ADU build costs $150,000–$500,000 all-in in 2026, depending on size, city, and finish level. The national median is roughly $260,000 for a 700–900 sq ft unit. Garage conversions run 40–60% lower ($80K–$180K).
What is included in ADU construction cost?
All-in ADU construction cost covers design and architecture (8–12% of total), permits and city fees ($4K–$25K), sitework and utility connections ($15K–$60K), framing and core construction (45–55% of total), interior finishes (15–20%), and soft costs like insurance, financing fees, and contingency (10–15%).
How much does ADU construction cost per square foot in 2026?
ADU construction costs $300–$600 per square foot in 2026 in major US metros. Coastal California cities sit at the top ($500–$650/sqft in the Bay Area, $400–$550/sqft in LA/SD). Mid-tier markets (Denver, Austin, Raleigh) run $250–$400/sqft. Garage conversions can come in as low as $150–$250/sqft.
Why does ADU construction cost so much?
ADUs are expensive per square foot because the fixed costs — design, permits, foundation, utility connections, full bath, full kitchen — get amortized across only 400–1,200 sq ft. A single-family home spreads those same fixed costs across 2,000+ sq ft, so the per-sqft cost looks lower even when the total dollars are higher.
How do I lower my ADU construction cost?
Five proven ways: (1) use pre-approved plans where your city offers them (saves $8K–$20K design + 4–8 weeks), (2) convert an existing garage instead of building new ($80K–$180K vs $250K+), (3) choose prefab or modular (15–25% cheaper than site-built), (4) pick a 1-bedroom under 800 sq ft (kitchens and baths drive cost), (5) bundle financing with your existing mortgage via cash-out refi for the lowest blended rate.