Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your San Diego ADU cost →Building an ADU in San Diego costs between $120,000-$300,000 for new construction, with per-square-foot costs averaging $180-$350. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $70,000-$160,000, while prefab/modular ADUs fall in between at $90,000-$220,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | $3,500-$12,000 |
| Impact Fees | Waived for units under 750 sq ft |
| Site Prep & Foundation | $10,000 – $35,000 |
| Framing & Structure | $15,000 – $45,000 |
| Plumbing | $8,000 – $20,000 |
| Electrical | $5,000 – $15,000 |
| HVAC | $3,000 – $8,000 |
| Interior Finishes | $15,000 – $40,000 |
Quotes for the same ADU commonly vary 20–40% between builders. Get up to 3 free quotes from ADU builders serving San Diego — no obligation.
Get San Diego builder quotes →Permit fees in San Diego are $3,500-$12,000. The review timeline is 60 days (often faster), with plan check: Standard plan check included. Impact fees are Waived for units under 750 sq ft. Pre-approved plans: Yes — companion unit program with pre-approved designs.
| 1-Bedroom Rent | $1,600-$2,200/month |
| 2-Bedroom Rent | $2,000-$2,800/month |
| Annual Rental Income (est.) | $22,800/year |
| Payback Period (est.) | 9.2 years |
| Short-Term Rental | Not allowed for ADUs — minimum 31-consecutive-day lease (Information Bulletin 400); JADUs are barred from short-term rental |
| Overall ROI Estimate | 7-11% annual return |
A typical ADU in San Diego generates approximately $22,800 per year in rental income based on average 1-bedroom rents. At an average construction cost of $210,000, the estimated payback period is 9.2 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in San Diego and varies by market (often less than build cost).
1. Garage conversions save 40-60% vs new construction since the shell already exists. Average cost in San Diego: $70,000-$160,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $90,000-$220,000.
3. Pre-approved plans — available in San Diego, which can save $3,000-$10,000 in design costs and 2-3 months in review time.
4. State grants — California's CalHFA ADU grant (up to $40K) is currently paused; check calhfa.ca.gov/adu for status and your state for active programs.
5. Get multiple bids — ADU contractor pricing varies 20-40% for the same project. We recommend getting at least 3 quotes.
Compare prices from local ADU contractors in your area. Free, no-obligation estimates.
Find ADU Contractors →