Garage conversion ADUs are hands-down the most popular and cost-effective way to add livable square footage or rental income in San Diego. With the removal of owner-occupancy requirements and streamlined permitting, garage conversions have become one of our most requested project types.
Why Garage Conversions Are Exploding in San Diego
Lower cost: At $150–$250/sq ft versus $300–$450/sq ft for new construction, a 400 sq ft garage conversion runs $60,000–$100,000 vs. $120,000–$180,000 for a detached ADU.
Simpler permitting: The footprint already exists. No new foundation, no grading, minimal structural work. Permitting typically takes 4–8 weeks versus 3–6 months for new construction.
Utility connections exist: Electrical panel, water, and sewer are usually close or already accessible.
What a Garage Conversion Actually Involves
1. Structural: Garage slabs are typically 4" thick and set below the adjacent floor — usually needs leveling or pouring a new section. Walls need insulation and interior framing.
2. Energy efficiency: California Title 24 energy requirements apply. Insulation, dual-pane windows, and energy-efficient HVAC are mandatory.
3. Egress: Minimum window sizes for sleeping areas are strictly enforced. At least one exterior door is required.
4. Parking replacement: California law prohibits cities from requiring replacement parking for converted garages. San Diego complies with this.
Garage Conversion Costs Breakdown
| Item | Typical Cost |
|---|---|
| Demolition and framing | $5,000 – $10,000 |
| Insulation and drywall | $4,000 – $8,000 |
| Electrical (new panel or sub-panel) | $3,000 – $8,000 |
| Plumbing (for kitchen/bath) | $8,000 – $20,000 |
| HVAC mini-split system | $3,000 – $6,000 |
| Flooring | $3,000 – $7,000 |
| Kitchen and bath finishes | $10,000 – $25,000 |
| Permits and fees | $3,000 – $8,000 |
ROI on Garage Conversion ADUs
In San Diego, a finished 1-bedroom garage conversion ADU rents for $1,800–$2,400/month. On an $80,000 conversion, that's a 27–36% annual cash-on-cost return — making it one of the best real estate investments available.
