The complete guide to building an ADU in San Diego. Costs, permits, timeline, financing, and ROI — everything you need to know before starting.
ADUs (Accessory Dwelling Units) are transforming San Diego properties. Whether for rental income, multigenerational living, or a home office, this guide covers everything you need to know.
What is an ADU?
An ADU is a secondary housing unit on a residential lot. California law now allows ADUs on most single-family properties. Types include:
- Detached ADU: Standalone unit, up to 1,200 sq ft
- Attached ADU: Connected to main house
- Garage Conversion: Transform existing garage
- Junior ADU (JADU): Within existing home, up to 500 sq ft
ADU Costs in San Diego (2025)
Garage Conversion: $80,000-$150,000
Detached ADU (500 sq ft): $150,000-$250,000
Detached ADU (1,000 sq ft): $250,000-$350,000
Junior ADU: $50,000-$100,000
ADU Timeline
- Design & permits: 2-4 months
- Construction: 4-8 months
- Total: 6-12 months
ROI & Rental Income
San Diego ADU rental rates (2025):
- Studio ADU: $1,500-$2,000/month
- 1-bedroom ADU: $2,000-$3,000/month
- 2-bedroom ADU: $2,500-$4,000/month
At $2,500/month, an ADU generates $30,000/year — paying for itself in 5-10 years while increasing property value by 20-30%.
Financing Options
Home Equity: HELOC or home equity loan
Cash-out refinance: Tap existing equity
Construction loan: Short-term financing
CalHFA ADU Grant: Up to $40,000 for qualifying homeowners
San Diego ADU Requirements
- 4-foot side/rear setbacks (typically)
- 16-foot height limit (detached)
- No owner-occupancy requirement
- Separate entrance required
- Kitchen, bathroom, and living space
Ready to build? Explore our ADU construction services or learn about ADU permits.
Ready to Start Your Project?
Contact One Stop Builders for a free consultation.
