Zoning & Size Limits
| Requirement | San Francisco, CA | San Diego, CA |
|---|
| Allowed Zones | RH-1, RH-2, RH-3, RM, RTO zones and most residential distric | All residential zones; also allowed in some commercial mixed |
| Max Size (Detached) | 1,200 sq ft (state minimum; local program caps at 850-1,000 sq ft) | 1,200 sq ft |
| Max Size (Attached) | 1,000 sq ft or 50% of primary dwelling | 1,200 sq ft or 50% of primary dwelling |
| Max Height | 25 ft for detached ADUs | 25 ft (2 stories) |
| Parking Required | No parking required | No parking required |
| Owner Occupancy | Not required | Not required |
Setback Requirements
| Setback | San Francisco, CA | San Diego, CA |
|---|
| Rear Setback | 4 ft minimum | 4 ft |
| Side Setback | 4 ft minimum | 4 ft |
| Front Setback | Must meet zone's front setback requirement | Per underlying zone |
Permits & Timeline
| Detail | San Francisco, CA | San Diego, CA |
|---|
| Permit Timeline | 60-day review period (state-mandated) | 60 days (often faster) |
| Permit Fees | $5,000-$20,000 depending on scope | $3,500-$12,000 |
| Impact Fees | Waived for units under 750 sq ft | Waived for units under 750 sq ft |
| Pre-Approved Plans | Yes — SF has pre-approved ADU plan sets | Yes — companion unit program with pre-approved des |
Construction Costs
| Cost | San Francisco, CA | San Diego, CA |
|---|
| Avg Build Cost | $200,000-$450,000 | $120,000-$300,000 |
| Cost Per Sq Ft | $300-$500 | $180-$350 |
| Garage Conversion | $120,000-$250,000 | $70,000-$160,000 |
| Prefab ADU | $150,000-$350,000 | $90,000-$220,000 |
Rental Income Potential
| Rental | San Francisco, CA | San Diego, CA |
|---|
| 1BR Avg Rent | $2,200-$3,200/mo | $1,600-$2,200/mo |
| 2BR Avg Rent | $2,800-$4,000/mo | $2,000-$2,800/mo |
| Short-Term Rentals | Heavily regulated; 90-day annual cap for unhosted | Allowed with STRO license in certain zones |
| Est. ROI | 5-8% annual return | 7-11% annual return |
Which City Is Better for ADUs?
San Francisco scores 9/10 while San Diego scores 9/10 on our ADU-friendliness index.
Both cities offer viable ADU development opportunities — the best choice depends on your specific property, budget, and goals.
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