ADU Permit Requirements: The Complete California Guide
Thinking about building an accessory dwelling unit (ADU) on your property? Before you start, it’s crucial to understand what an ADU permit is, why you need it, how to get it, and how much it costs in California. This guide answers all your questions so you can move forward confidently.
What Is an ADU Permit?
An ADU permit is official approval from your city or county building department to build, convert, or legalize an accessory dwelling unit on your property. It ensures your ADU complies with California Building Standards, zoning laws, and safety codes.
Do You Need a Permit for an ADU in California?
Yes. California law requires a permit for:
- Detached new-build ADUs
- Garage conversion ADUs
- Junior ADUs (JADUs)
- Interior conversions within existing homes
Building without a permit can lead to severe legal and financial consequences.
Why Do You Need a Permit for an ADU?
- ✅ Ensures your ADU is legal and safe
- ✅ Protects property value and insurability
- ✅ Avoids fines, penalties, or forced demolition
- ✅ Allows legal rental or refinancing
How to Get an ADU Permit in California
1. Review Local Zoning Rules
Each city has unique zoning regulations. Confirm:
- Which ADU types are allowed in your zone
- Minimum lot size requirements
- Setback rules (distance from property lines)
- Maximum height and square footage limits
💡 Tip: Use the California HCD ADU Handbook for detailed state guidance.
2. Prepare Professional ADU Plans
Most permit applications require:
- Site Plan: Shows ADU placement on property
- Floor Plans: Interior room layouts
- Elevations & Sections: Exterior views and structural details
- Title 24 Energy Compliance Report
- Structural Calculations (if needed)
✅ Using a professional ADU designer prevents costly plan rejections.
3. Submit Your Permit Application
Submit your application online or in person with:
- Completed city/county forms
- Construction drawings and reports
- Permit application and plan check fees
4. Address Plan Check Corrections
The building department may issue corrections. Respond promptly to keep your approval timeline short.
5. Receive Approval & Start Construction
After approval, your permit allows legal construction. Schedule inspections at each stage to remain compliant.
✅ Using a professional ADU designer or an ADU builder in Sacramento prevents costly plan rejections and ensures your project meets all local requirements from the start.
How Much Does an ADU Permit Cost in California?
Permit costs vary by city and ADU type. Typical ranges:
| ADU Type | Estimated Permit Cost |
| Garage Conversion | $3,000 – $8,000 |
| Detached New ADU | $5,000 – $15,000+ |
| Junior ADU (JADU) | $1,000 – $3,000 |
✅ Included in these costs:
- Plan check fees
- Building permit fees
- Impact fees (often waived for ADUs under 750 sq ft)
- Utility connection fees (if applicable)
🔗 Check your city’s ADU permit fee schedule for exact pricing.
How Long Does It Take to Get an ADU Permit?
By law, California cities must approve or deny a complete ADU application within 60 days. Realistically:
- Well-prepared plans: 2–3 months
- Incomplete submissions: 4–6+ months
⏳ Factors affecting timelines:
- Missing documents or errors in plans
- High volume of permit applications
- Delays in applicant responses
What Happens If You Build an ADU Without a Permit in California?
Building without an ADU permit can result in:
- ❌ Stop-work orders
- ❌ Daily fines and penalties
- ❌ Forced removal or demolition
- ❌ Problems selling or refinancing your property
- ❌ Insurance coverage denial if damages occur
💡 Permitting your ADU upfront is always safer and more affordable than retroactive legalization.
How to Permit an Unpermitted ADU
If your ADU was built without permits:
- Hire a designer or permit service to create as-built plans
- Submit for a retroactive permit with your city
- Make modifications to meet current codes if required
- Schedule inspections to legalize the unit
How to Apply for an ADU Permit
✅ Steps to apply:
- Contact your city building department
- Review zoning and code requirements
- Prepare professional construction and energy plans
- Complete and submit all application forms
- Pay plan check and permit fees
- Address plan check corrections
- Receive permit approval
Can I Hire a Company to Handle My ADU Permitting Process?
Yes. Many homeowners choose to hire a permit service company or ADU permit contractor to handle the entire permitting process. These professionals manage:
- Preparing accurate architectural and structural plans
- Ensuring all documents meet local building and zoning codes
- Submitting applications to the city or county
- Addressing plan check corrections quickly
- Scheduling necessary inspections
💡 Tip: If you want a stress-free experience, consider working with an experienced ADU builder in Sacramento who offers design, drafting, and permit services as part of their package. This ensures your ADU is approved faster and built to code from the start.
FAQs About ADU Permits in California
How much does it cost to permit an ADU?
Between $1,000 for JADUs to over $15,000 for large detached units, depending on your city and project complexity.
What happens if I build an ADU without a permit?
You risk stop-work orders, fines, forced demolition, and legal issues. Legalizing later often costs more.
How long does it take to get an ADU permit?
Typically 2–4 months, depending on plan quality and city workload.
How to get an ADU permit in California?
Prepare professional plans, complete city applications, pay required fees, and submit for plan check. Address corrections promptly.
How to permit an unpermitted ADU?
Hire a designer for as-built plans, apply for retroactive permits, make code modifications, and pass inspections to legalize the unit.
Final ADU Permit Checklist
✅ Confirm zoning and setback rules
✅ Hire professional design and drafting services
✅ Submit complete applications with all required documents
✅ Pay permit and plan check fees
✅ Address plan check corrections promptly
✅ Schedule inspections throughout construction
Ready to Start Your ADU Project Legally?
Navigating ADU permits can be complex, but TOV Plans simplifies the process. We create accurate drafting, code-compliant plans, and handle your permitting paperwork so you can build your ADU confidently and stress-free.
👉 Contact TOV Plans today for a free consultation and ensure your ADU permit is approved quickly and efficiently.
