ADU Cost Comparison: Top 10 US Cities (2026)
Compare ADU permit fees, impact fees, and total estimated government costs across the 10 largest ADU markets in the US. Data from official city fee schedules.
Side-by-Side Comparison
ADU Cost Comparison: Top 10 US Cities (2026)
| Los AngelesCalifornia | San FranciscoCalifornia | San DiegoCalifornia | PortlandOregon | SeattleWashington | AustinTexas | DenverColorado | SacramentoCalifornia | San JoseCalifornia | BoiseIdaho | |
|---|---|---|---|---|---|---|---|---|---|---|
| Plan Check Fee | $500–$3,000 | $800–$3,500 | $600–$2,500 | $1,500–$4,000 | $2,000–$5,000 | $300–$2,000 | $1,500–$4,500 | $500–$2,200 | $700–$2,800 | $300–$1,500 |
| Building Permit Fee | $1,500–$5,000 | $2,000–$6,000 | $1,500–$5,500 | $1,200–$3,500 | $1,500–$4,000 | $1,000–$4,000 | $1,200–$3,500 | $1,200–$4,500 | $1,800–$5,500 | $800–$3,500 |
| Impact / System Development Fees | Waived under 750 sq ft | Waived under 750 sq ft | Waived under 750 sq ft | $10,000–$25,000 (SDCs: transportation, parks, utilities) | $3,700–$7,400 (school impact fees) | $3,000–$8,000 (water/wastewater impact fees) | $3,000–$6,000 (school impact fees) | Waived under 750 sq ft | Waived under 750 sq ft | Varies (water/sewer connection fees) |
| Total Estimated Government Fees | $2,000–$8,000 | $3,000–$10,000 | $2,500–$9,000 | $13,000–$33,000 | $7,700–$19,400 | $3,000–$15,000 | $6,000–$16,000 | $2,000–$7,500 | $2,500–$8,500 | $1,500–$6,000 |
| Permit Timeline | 2-4 weeks (LADBS ADU Express) | 2-6 weeks | 3-6 weeks | 4-8 weeks (2-4 with pre-approved plans) | 4-8 weeks (1-3 with pre-approved plans) | 2-4 months | 4-8 weeks (60-day state mandate) | 3-5 weeks | 3-6 weeks | 4-8 weeks |
| School Impact Fees (ADUs under 750 sq ft) | Waived | Waived | Waived | May apply | $3,700–$7,400 | None | $3,000–$6,000 | Waived | Waived | None |
Key Differences
ADU government fee costs vary dramatically across the top 10 US ADU markets, and the differences can amount to tens of thousands of dollars. Portland stands out as the most expensive in total government fees — its System Development Charges (SDCs) for transportation, parks, and utilities add $10,000–$25,000 to every new ADU project on top of standard permit fees, totaling $13,000–$33,000. Seattle and Denver are mid-tier at $7,700–$19,400 and $6,000–$16,000 respectively, primarily due to school impact fees. California cities benefit from statewide impact fee waivers for ADUs under 750 sq ft (Government Code 65852.2(f)(3)), making Sacramento, Los Angeles, San Diego, and San Jose among the least expensive cities for ADU permit fees ($2,000–$10,000 range). San Francisco's higher base permit fees push it to $3,000–$10,000. Boise is the lowest-cost city in this comparison at $1,500–$6,000 total, with no school impact fees and water/sewer connection fees as the primary variable. Austin's fees are moderate at $3,000–$15,000, with water/wastewater impact fees creating the largest variable. Permit timeline correlates somewhat with fee complexity: Sacramento and LA have the fastest timelines (2-6 weeks) while Austin's review process takes 2-4 months — the longest in this group.
Cost Comparison
Beyond government fees, construction costs vary even more dramatically than permit fees. A comparable 750 sq ft detached ADU costs approximately: - Bay Area (SF, San Jose): $250,000–$450,000+ - Los Angeles: $180,000–$350,000 - Seattle: $200,000–$380,000 - Portland: $160,000–$320,000 - Denver: $160,000–$330,000 - Sacramento: $150,000–$290,000 - Austin: $150,000–$300,000 - Boise: $120,000–$250,000 The total cost to a homeowner — construction + government fees — can range from under $125,000 (small ADU in Boise) to over $500,000 (full 1,200 sq ft ADU in San Francisco). However, Bay Area rental income potential may justify the premium: San Jose ADUs can command $2,500–$3,500/month, while Boise might yield $1,000–$1,600/month.
Our Verdict
For lowest government fee burden, California cities with ADUs under 750 sq ft are the cheapest thanks to statewide fee waivers. Sacramento and Boise are the most cost-effective overall when combining permit fees with reasonable construction costs. Portland is the most expensive for fees alone due to SDC burden. For the best return on investment considering both costs and rental income, Bay Area cities (San Jose, San Francisco) generate the highest rents despite the highest construction costs. The sweet spot for cost vs income is often Sacramento or Denver — moderate construction costs, reasonable fees, and solid rental demand.
Explore Each City
Frequently Asked Questions
Which US city has the lowest ADU permit fees?
Boise, Idaho has the lowest total government fees at $1,500–$6,000, with no school impact fees and only water/sewer connection fees as variables. Among California cities, Sacramento ($2,000–$7,500) and Los Angeles ($2,000–$8,000) are the cheapest thanks to statewide ADU fee waivers for units under 750 sq ft.
Why are Portland ADU fees so much higher than other cities?
Portland charges System Development Charges (SDCs) for transportation, parks, and water/sewer infrastructure — these typically add $10,000–$25,000 to ADU project costs on top of standard permit fees. SDCs are Portland's mechanism for funding infrastructure. California prohibits these charges for ADUs under 750 sq ft under state law. SDC deferrals are available for affordable housing ADUs in Portland.
Are California ADU permit fees really that low?
Yes, for ADUs under 750 sq ft. California Government Code 65852.2(f)(3) waives impact fees and school developer fees for ADUs under 750 sq ft statewide. Permit fees (plan check + building permit) are the only government costs, running $2,000–$10,000 depending on project value and city. ADUs 750+ sq ft are subject to school developer fees.
Does a faster permit timeline mean lower total costs?
Not directly — permit fees are separate from timelines. However, faster permitting reduces carrying costs if you're financing construction, and reduces delays to receiving rental income. Los Angeles's 2-4 week ADU Express timeline and Sacramento's 3-5 weeks are among the fastest, while Austin's 2-4 month timeline creates longer wait periods before rental income begins.
Source: PropertyZoned Editorial Research. Last verified April 5, 2026. View source