Why Do You Need an ADU Permit?
Permits are legally required in California for all ADU types—whether you're building from the ground up or converting existing space. ADU permits ensure that:
The unit complies with California Building Code (CBC)
Zoning laws and fire safety standards are followed
Structural, electrical, plumbing, and energy systems meet current regulations
💼 Types of ADU Permits & Associated Costs
| Permit Type | Estimated Cost Range (2025) |
| Building Permit | $1,500 – $6,000 |
| Plan Review Fees | $500 – $2,000 |
| Zoning/Planning Permit | $250 – $1,500 |
| Electrical Permit | $100 – $1,000 |
| Plumbing/Mechanical Permit | $150 – $1,500 |
| School Impact Fees | $0 – $4,000+ (waived for ADUs ≤ 750 sq ft) |
| Utility Hookup Fees | $0 – $5,000+ (varies by utility) |
| Fire Department Review | $200 – $1,000 |
| Total Permit Costs | ✅ $3,000 to $15,000+ |
🧾 Cost Factors That Influence ADU Permit Fees
1. ADU Size and Type
Smaller ADUs (≤ 750 sq ft) qualify for fee waivers under state law.
- Detached units typically cost more to permit than conversions or JADUs.
2. Location (City or County)
Each city and county has different fee structures. For example:
Los Angeles may charge more for plan checks and utility fees.
San Jose and San Diego offer fee reductions for specific ADU projects.
3. New Construction vs. Conversion
Garage or basement conversions often have lower permit fees than new builds.
Conversions may qualify for utility fee waivers.
4. Utility Requirements
Upgrading sewer, water, or electrical systems can trigger additional permit and connection fees.
Some cities waive these fees if existing systems are adequate.
🏘️ How to Estimate ADU Permit Costs in Your City
To get an accurate estimate:
Visit your local planning or building department’s website
Use any available ADU fee calculators (many cities have them)
Contact the city’s permit counter for a personalized breakdown
Request a copy of the ADU fee schedule if not publicly posted
✅ Tips to Reduce ADU Permit Costs
Stay under 750 sq ft to qualify for mandatory fee waivers (impact & school fees)
Use pre-approved ADU plans available in cities like San Jose, Fresno, and LA
Convert existing structures (e.g., garage or basement) to avoid new utility connection fees
Apply early in the year to take advantage of limited-time incentives or fee reduction programs
📌 Real-World Examples of ADU Permit Costs (2025)
| City | Approx. Permit Cost | Notes |
| Los Angeles | $8,000 – $15,000 | Higher utility hookup fees; incentives for low-income ADUs |
| San Diego | $4,000 – $10,000 | Discounts for pre-approved plans and ADUs under 750 sq ft |
| Sacramento | $3,500 – $8,000 | Conversion ADUs cost less; some school fee exemptions |
| San Jose | $5,000 – $12,000 | Offers streamlined permitting and planning grants |
| Oakland | $4,000 – $9,000 | Waives impact fees for affordable ADU units |
