With housing shortages affecting affordability in California, San Diego County has embraced Accessory Dwelling Units (ADUs) and Junior Accessory Dwelling Units (JADUs) as a flexible, legal way to increase housing supply. Whether you're a homeowner seeking extra rental income or a family needing multi-generational living space, understanding the local rules is crucial.
What is an ADU?
An Accessory Dwelling Unit (ADU) is a secondary housing unit built on the same lot as a primary residence. Also known as granny flats, in-law units, or casitas, ADUs can be detached, attached, or converted from existing space (like a garage or basement).
What is a Junior ADU (JADU)?
A Junior ADU (JADU) is a smaller unit (up to 500 sq. ft.) created within the primary home, such as converting a bedroom or portion of the house. Unlike full ADUs, JADUs must be located within the existing residence and require an efficiency kitchen but not a full bathroom.
Key Benefits of ADUs and JADUs in San Diego County
✅ Increase Property Value
✅ Generate Rental Income
✅ Provide Housing for Family or Tenants
✅ Sustainable Urban Growth
✅ Reduced Permit Barriers Under State Law
San Diego County ADU Regulations (As of 2025)
| Category | ADU | JADU |
|---|---|---|
| Max Size | Up to 1,200 sq. ft. | Up to 500 sq. ft. |
| Kitchen Required? | Yes | Efficiency kitchen only |
| Bathroom Required? | Yes | Not required (may share with main) |
| Parking Requirements | Typically waived near transit | None |
| Owner-Occupancy Required? | No (until 2025 ends) | Yes |
| Fire Sprinklers? | Not required if not in primary | Not required |
| Zoning Restrictions | Allowed in all residential zones | Allowed in all residential zones |
Permit Process for Building an ADU/JADU in San Diego County
- Preliminary Site EvaluationDetermine zoning, lot size, setbacks, and utility availability.
- Design and PlanningCreate architectural plans meeting local codes.
- Submit for PermitsApply through the County of San Diego Planning & Development Services.
- Approval and FeesFees vary depending on unit size and type. In some areas, development and impact fees are waived.
- Construction and InspectionHire licensed contractors and schedule inspections as required.
Cost to Build an ADU in San Diego
The cost to build an ADU in San Diego County ranges from $150,000 to $350,000, depending on:
Type (detached vs. garage conversion)
Size and materials
Utility connections
Site grading and accessibility
JADUs are much more affordable, often under $75,000, due to reduced construction scope.
Top ADU Builders in San Diego County
If you're looking for professional guidance, here are some reputable ADU specialists:
FortuneADU – Offering full-service ADU design, permitting, and construction tailored for San Diego County.
Modative – Focused on modern prefab ADUs.
SnapADU – Known for customized ADU planning and project management.
Maxable Space – Helps homeowners through the entire ADU journey.
JADU vs. ADU – Which One Should You Build?
| Factor | Choose ADU | Choose JADU |
|---|---|---|
| Budget | Higher budget available | Lower-cost solution |
| Separate Living Space | Needed (for renters or guests) | Not essential |
| Rental Income Potential | Higher (full unit) | Lower (smaller, shared bath) |
| Construction Scope | Major construction acceptable | Minimal alterations preferred |
FAQ
Final Thoughts
Building an ADU or JADU in San Diego County is more accessible than ever thanks to updated California laws and reduced permit barriers. Whether you're looking to generate rental income, increase property value, or house a loved one, an ADU or JADU can be a smart investment in 2025.
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