# ADU Laws in San Diego 2025: Complete Guide to Building Your Accessory Dwelling Unit
Thinking about building an ADU in San Diego? Here's everything you need to know about permits, costs, and regulations.
See our complete ADU builder cost guide for San Diego for detailed 2026 pricing.
What is an ADU?
An Accessory Dwelling Unit (ADU) is a secondary housing unit on a single-family residential lot. In San Diego, ADUs are also called:
- Granny flats
- In-law suites
- Backyard cottages
- Casitas
San Diego ADU Rules (Updated 2025)
Size Limits
| ADU Type | Maximum Size |
|---|---|
| Detached ADU | 1,200 sq ft |
| Attached ADU | 50% of main home or 1,200 sq ft (whichever is less) |
| Junior ADU (JADU) | 500 sq ft (within existing home) |
Setback Requirements
- Rear setback: 4 feet
- Side setback: 4 feet
- No setback required for conversions of existing structures
Parking
- No additional parking required for ADUs in San Diego!
- This changed in 2020 and makes ADUs much more feasible
Height Limits
- Detached ADU: 16 feet (can be taller in some zones)
- Attached ADU: Must match main home height
How Much Does an ADU Cost in San Diego?
| ADU Type | Cost Range | Timeline |
|---|---|---|
| Garage Conversion | $80,000 - $150,000 | 3-4 months |
| Prefab/Modular ADU | $150,000 - $250,000 | 4-6 months |
| Custom Built ADU | $200,000 - $400,000+ | 6-12 months |
Cost Breakdown:
- Design & Permits: $10,000 - $25,000
- Foundation: $15,000 - $30,000
- Construction: $150 - $400 per sq ft
- Utilities hookup: $10,000 - $30,000
- Landscaping: $5,000 - $15,000
ADU Benefits for San Diego Homeowners
1. Rental Income
Average ADU rent in San Diego: $1,800 - $3,000/month
- Annual income potential: $21,600 - $36,000
- Can offset mortgage significantly
2. Property Value Increase
ADUs typically add 20-30% to property value
- $500K home → Could become $650K with ADU
3. Multi-Generational Living
- Housing for aging parents
- Space for adult children
- Guest accommodations
4. Work From Home Space
Perfect home office that's separate from main living areas
San Diego ADU Permit Process
Step 1: Pre-Application Meeting (Optional)
Meet with city planning to discuss your project
Step 2: Submit Plans
- Site plan
- Floor plan
- Elevations
- Structural calculations
Step 3: Plan Review (60-90 days)
City reviews for compliance with codes
Step 4: Permit Issued
Pay fees and receive building permit
Step 5: Construction + Inspections
Build ADU with required inspections
Step 6: Final Inspection
Certificate of occupancy issued
Total timeline: 6-12 months from start to finish
San Diego ADU Financing Options
1. Home Equity Loan/HELOC
Use your home's equity to fund construction
2. Construction Loan
Converts to permanent mortgage after build
3. Cash-Out Refinance
Refinance existing mortgage and pull cash for ADU
4. ADU-Specific Loans
New products designed for ADU construction
5. CalHFA ADU Grant Program
Up to $40,000 for qualifying homeowners
Popular ADU Designs in San Diego
1. Modern Studio (400-500 sq ft)
- Open floor plan
- Murphy bed
- Compact kitchen
- Great for rentals
2. One-Bedroom (600-800 sq ft)
- Separate bedroom
- Full kitchen
- Living area
- Most popular choice
3. Two-Bedroom (900-1,200 sq ft)
- Family-friendly
- Two full baths
- Premium rental income
Why Choose Cali Dream Construction for Your ADU?
✅ Full-Service: Design, permits, construction
✅ Local Expertise: We know San Diego codes inside and out
✅ Transparent Pricing: Fixed bids, no surprises
✅ Quality Built: Craftsmanship that lasts
✅ On-Time Delivery: We meet our deadlines
Our ADU Process:
- planning session and site visit
- Custom design based on your needs
- Handle all permits and approvals
- Build your ADU with regular updates
- Final walkthrough and handover
Get Started on Your San Diego ADU
Ready to add an ADU to your property? Let's talk about your options.
📞 Call: (858) 434-7166
📧 Email: team@calidreamconstruction.com
🌐 Website: calidreamconstruction.com
planning sessions for San Diego County homeowners
Ready to Start Your San Diego Remodel?
Request in-person project planning from our licensed general contracting team. CSLB #1054602.
Request planning session(858) 434-7166
Next Cost And Scope Planning
Use these related guides and project examples to turn the topic above into a realistic budget, scope, and permit plan.