Updated April 2026
ADU Impact Fees: $0–$30,000 — What You'll Pay by City (2026)
The complete guide to ADU development impact fees — from California's SB 13 waiver to city-by-city fee schedules and proven reduction strategies.
Quick Answer
Most ADUs under 750 sq ft pay $0 in impact fees in California (SB 13 waiver). Larger ADUs (750–1,200 sf) pay proportional fees ranging from $2,000 to $30,000+ depending on your city.
What Are ADU Impact Fees?
Development impact fees are one-time charges collected by cities and counties when you pull a building permit. They are designed to fund the public infrastructure your new ADU will use — parks, roads, fire stations, police services, schools, water systems, and sewer capacity. Impact fees are entirely separate from permit fees (which fund plan review) and utility hookup fees (which fund physical connections). For many ADU builders, impact fees represent the single largest permit-related cost — sometimes exceeding the cost of the permit itself by 5x or more.
The amount you pay depends on your city's fee schedule, your ADU's size, and what state laws apply. In California, SB 13 has dramatically reduced the impact fee burden for small ADUs. In other states, fees are set entirely by local governments with no statewide waiver.
Parks & Recreation
Funds new park space and recreation facilities. Typically $500–$5,000 per ADU depending on city population growth goals.
Transportation
Funds road improvements and traffic mitigation for new residents. Typically $1,000–$8,000 per ADU.
Fire & Police
Funds emergency services capacity for new residents. Typically $200–$3,000 per ADU, often split between fire and police budgets.
Sewer & Water Capacity
Funds utility system expansion for new demand. Often the largest single fee category at $2,000–$12,000 per ADU.
California SB 13 Impact Fee Waiver
California Senate Bill 13 (signed 2019) requires all cities and counties in California to waive impact fees for ADUs under 750 square feet. For larger ADUs, fees must be proportional — calculated as a ratio of the ADU's size divided by the primary home's size. This law has saved California ADU builders millions of dollars and is one of the most powerful ADU-friendly policies in the country.
| ADU Type & Size | Impact Fee Treatment | Legal Basis |
|---|---|---|
| ADU under 750 sq ft | All impact fees waived | SB 13 (2019) |
| ADU 750–1,200 sq ft | Proportional fees (ADU sf ÷ primary home sf) | SB 13 (2019) |
| JADU under 500 sq ft | All fees waived, incl. school fees | SB 543 (2025) clarified |
Sunset Date: The SB 13 waiver runs through December 31, 2026. Check with your local planning department for the latest status and any pending legislative extensions.
City-by-City ADU Impact Fee Comparison
Impact fees vary dramatically by city. California cities benefit from the SB 13 waiver for small ADUs, while cities in other states set their own rules. Here's what to expect in 12 major metro areas:
| City | State | ADU < 750 sf | ADU 750+ sf | Notes |
|---|---|---|---|---|
| San Diego | CA | $0 | $5,000–$15,000 | SB 13 waiver applies; proportional above 750 sf |
| Los Angeles | CA | $0 | $3,000–$12,000 | SB 13 waiver; city also waives some school fees |
| San Francisco | CA | $0 | Varies | City waives many impact fees for all ADU sizes |
| San Jose | CA | $0 | $3,000–$10,000 | Pre-approved plans may further reduce fees |
| Sacramento | CA | $0 | $1,000–$5,000 | Lower fee schedule than coastal CA cities |
| Portland | OR | $15,000–$20,000 | $15,000–$20,000 | SDC waiver program available — up to $20K saved |
| Seattle | WA | $0–$2,000 | $2,000–$5,000 | Many waivers available; check with SDCI |
| Denver | CO | $1,000–$4,000 | $3,000–$8,000 | No statewide waiver; fees set by city ordinance |
| Austin | TX | $2,000–$5,000 | $5,000–$10,000 | Impact fees vary by location within city limits |
| Miami | FL | $3,000–$5,000 | $5,000–$8,000 | County-level fees may stack on top of city fees |
| Scottsdale | AZ | $1,000–$2,000 | $2,000–$4,000 | Relatively low fee schedule; garage conversions lower |
| Raleigh | NC | $2,000–$4,000 | $4,000–$8,000 | Growing city with increasing infrastructure fees |
Fee ranges are estimates. Verify with your local planning department before budgeting. Updated April 2026.
Calculate Your Total ADU Cost
Get a personalized estimate that includes impact fees, permit fees, utility hookups, and construction costs for your city.
Get Your Estimate6 Ways to Reduce ADU Impact Fees
Build Under 750 sq ft (CA)
In California, keeping your ADU under 750 square feet triggers an automatic SB 13 waiver — $0 in impact fees. This single decision can save $5,000–$15,000 or more.
Build a JADU
Junior ADUs under 500 sq ft are fully exempt from all impact fees in California, including school fees. SB 543 (2025) confirmed this exemption with no ambiguity.
Check Local Waiver Programs
Many cities offer additional impact fee waivers for affordability commitments, family member occupancy, or garage conversions. Always ask your planning department what programs are available.
Use Pre-Approved Plans
Some cities that offer pre-approved ADU plan programs also reduce or streamline fee schedules for those plans. San Jose's program, for example, can reduce total permit costs significantly.
Portland SDC Waiver ($20K Saved)
Portland's System Development Charge (SDC) waiver program can eliminate up to $20,000 in SDC fees for qualifying ADU projects. You must apply before permit issuance — retroactive applications are not accepted.
Appeal Incorrect Calculations
If your fees are based on wrong square footage or the city failed to apply a required waiver, you can appeal. File in writing, provide documentation, and request recalculation. Many errors are caught and corrected through appeals.
Impact Fees vs. Other ADU Fees
Impact fees are just one of several fee categories you'll encounter when building an ADU. Understanding how they differ helps you budget accurately and avoid surprises at permit issuance.
| Fee Type | When Paid | Funds | Typical Range |
|---|---|---|---|
| Impact Fees | At permit issuance | Public infrastructure (parks, roads, utilities) | $0–$30,000+ |
| Permit Fees | At permit issuance | Plan review and building inspections | $2,000–$8,000 |
| School Fees | At permit issuance | School district capital improvements | $2–$5 per sq ft |
| Utility Connection Fees | At utility connection | Physical hookups (water, sewer, electric) | $2,000–$15,000 |
Total fee burden at permit: $4,000–$50,000+ depending on city, ADU size, and applicable waivers.
Frequently Asked Questions
What are ADU impact fees?
ADU impact fees are one-time fees charged by cities and counties when you build an ADU to fund public infrastructure — parks, roads, fire stations, police, schools, water, and sewer systems. They are separate from building permit fees and plan check fees, and can be the single largest permit-related cost, ranging from $0 to $30,000 or more depending on your city and ADU size.
Are impact fees waived in California?
Yes. California SB 13 requires cities to waive all impact fees for ADUs under 750 square feet. ADUs between 750 and 1,200 square feet pay proportional fees. JADUs under 500 square feet are also fully exempt. This waiver runs through December 31, 2026.
How much are impact fees for an 800 sq ft ADU?
An 800 sq ft ADU in California pays proportional impact fees based on its size relative to the primary home. Fees typically range from $2,000 to $15,000 depending on your city. In high-fee cities like San Diego or San Jose, fees for an 800 sq ft ADU could reach $5,000–$12,000. Outside California, fees can be higher — Portland charges $15,000–$20,000 regardless of size, though a waiver program may apply.
Do JADUs pay impact fees?
No. Junior ADUs (JADUs) under 500 square feet are fully exempt from impact fees in California. SB 543 (2025) clarified that JADUs are completely exempt, including school fees for ADUs up to 500 square feet. This makes JADUs one of the most cost-effective ADU types from a fee perspective.
What's the difference between impact fees and permit fees?
Impact fees fund public infrastructure like parks, roads, and utilities — they're charged based on the new demand your ADU creates on those systems. Permit fees fund the city's plan review and inspection process. Both are paid at permit issuance, but they serve different purposes and are calculated differently. Permit fees are typically $2,000–$8,000 for an ADU; impact fees range from $0 to $30,000+.
Can I appeal impact fees?
Yes. If you believe your impact fees were calculated incorrectly — wrong square footage, wrong ADU type classification, or failure to apply a required waiver — you can appeal to your local planning or building department. File your appeal in writing, provide documentation of the error, and request a fee recalculation. Many cities have a formal appeals process. A permit expediter or local ADU contractor can help you identify calculation errors before you pay.
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