ADU Cost per Square Foot by Metro [2026]
Per-sqft rates for a typical 600 sq ft detached new-build ADU across 18 US metros, from $200/sf in the Sun Belt to $700/sf in the Bay Area.
Last updated: •Reviewed by the aduglossary editorial team
National average
$0/sf
$/sqft by metro · 600 sq ft detached new-build
Bars show the mid-point of each metro's $/sqft range. The dashed line is the national average ($384/sf).
🟠 highest-cost metro·🟢 lowest-cost metro·🟣 mid-range·tap any city for the full cost guide
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Full $/sqft range + permit fees by metro
Low and high per-sqft rates plus typical permit-fee window for a 600 sq ft detached build.
| Metro | $/sf low | $/sf high | All-in 600 sf |
|---|---|---|---|
| San Francisco / San Jose | $450 | $700 | $270K–$420K |
| Honolulu | $450 | $700 | $270K–$420K |
| Seattle | $420 | $620 | $252K–$372K |
| Los Angeles | $400 | $550 | $240K–$330K |
| Denver | $400 | $550 | $240K–$330K |
| San Diego | $380 | $520 | $228K–$312K |
| Portland | $350 | $500 | $210K–$300K |
| Sacramento | $300 | $420 | $180K–$252K |
| Phoenix / Scottsdale | $280 | $400 | $168K–$240K |
| Miami | $280 | $400 | $168K–$240K |
| Atlanta | $260 | $380 | $156K–$228K |
| Minneapolis | $240 | $380 | $144K–$228K |
| Nashville | $240 | $360 | $144K–$216K |
| Tampa | $240 | $360 | $144K–$216K |
| Austin | $220 | $380 | $132K–$228K |
| Raleigh | $230 | $350 | $138K–$210K |
| Dallas | $210 | $360 | $126K–$216K |
| Houston | $200 | $340 | $120K–$204K |
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<iframe src="https://aduglossary.com/adu-cost-per-square-foot/embed" width="100%" height="720" frameborder="0" loading="lazy" title="ADU cost per square foot by metro [2026] — ADUCosts"></iframe> <p><a href="https://aduglossary.com/adu-cost-per-square-foot" target="_blank" rel="noopener">Source: ADUCosts — ADU Cost per Sqft [2026]</a></p>
Why cost per sqft drops as ADUs get larger
Many homeowners assume a 400 sq ft ADU should be the cheapest option per square foot. The opposite is usually true. ADU builds carry a fixed-cost stack that doesn't scale with size:
- Permits and plan check — the same fee structure regardless of build size in most jurisdictions.
- Utility hookups — sewer, water, and electric tap-ins are the same trench and the same connection fee for a 400 or 1,200 sq ft unit.
- Design fees — an architect typically charges a flat fee or a fee floor that doesn't shrink proportionally.
- Mobilization and site setup — hauling equipment, erecting fences, and pulling licenses cost the same on day one regardless of footprint.
The result: a 400 sq ft ADU in Sacramento might run $400/sf, while an 800 sq ft ADU on the same lot lands at $340/sf. Total budget is higher for the bigger unit, but value-per-square-foot improves. This is why many homeowners size up to 600–800 sq ft when zoning allows.
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Per-sf math tells you what to budget; financing tells you what you can afford. Compare HELOC, construction-perm, RenoFi, and DSCR loans — or run a payment scenario in the ADU loan calculator.
Frequently asked questions
What is a typical ADU cost per square foot in 2026?
Across the US, ADU all-in costs run $200 to $700 per square foot in 2026. The national median is roughly $400/sf for a detached new-build, $300/sf for a garage conversion, and $200/sf for a basement conversion. The biggest swings come from labor markets and permit fees, not materials.
Why does cost per square foot go down as ADUs get larger?
Fixed costs (permits, utility hookups, design fees, mobilization) are roughly the same whether you build 400 or 1,200 sq ft. Spreading those costs over more square footage lowers the effective per-sf number. A 400 sq ft ADU often costs more per sq ft than an 800 sq ft build on the same lot.
Is cost per square foot a reliable budgeting tool?
It is useful for early feasibility but not for final budgeting. Two builds at the same per-sf number can differ by $30K–$50K once site conditions, foundation type, and finish level are factored in. Use per-sf to compare neighborhoods and ADU types; use a contractor bid for the final budget.
Which US cities have the highest ADU cost per square foot?
San Francisco, San Jose, Seattle, and Honolulu top the list at $450–$700+/sf for a 600 sq ft detached build. Los Angeles and San Diego run $380–$550/sf. Sacramento, Portland, and Phoenix are in the $280–$420/sf band. Texas metros (Houston, Austin, Dallas) and the Mountain West run $200–$380/sf.
What is included in the per-square-foot number?
Hard construction (labor + materials), soft costs (design, engineering, project management), and permits. It typically excludes land, demolition, lot-specific work like grading or retaining walls, and furnishings.
Does ADU type affect cost per square foot?
Yes — significantly. Detached new-build is the most expensive at $300–$700/sf because everything is new. Attached ADUs save 10–20% on shared walls. Garage conversions reuse the foundation and shell ($150–$350/sf). Basement conversions are cheapest at $100–$250/sf.
Source & method: Per-sqft rates derived from ADUCosts 2026 metro cost guides, normalized to a 600 sq ft detached new-build (all-in: design, permits, hard construction; excludes land, demolition, lot-specific site work, and furnishings). Tap any city above for its full local breakdown.
YMYL disclaimer: ADU costs are sensitive to lot conditions, finish level, contractor selection, and local labor rates. The figures on this page are general guidance for early feasibility — they are not a contractor quote, mortgage pre-approval, or financial advice. Confirm pricing with at least three local licensed builders and consult a licensed loan officer before committing to a budget.
Reviewed and last updated 2026-06-11 · Methodology aligns with ADUCosts 2026 city guides · Issue #105.
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