Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your San Antonio ADU cost →Building an ADU in San Antonio costs between $125,000-$320,000 for new construction, with per-square-foot costs averaging $225-$400. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $30,000-$90,000, while prefab/modular ADUs fall in between at $150,000-$300,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | FY2026 DSD fee schedule (rev. Oct 2025), new residential construction by size: $988 total basic permit fees for 501-1,000 sq ft, $1,022 for 1,001-1,250 and $1,201 for 1,251-1,500 sq ft (building, trade and sewer permits plus a $200 plan review). 100% waivable for income-qualified ADUs. |
| Impact Fees | The City itself charges no impact fee. SAWS water and wastewater impact fees (effective July 1, 2024; about $7,300-$12,000 per EDU combined, by service area) apply only if the ADU adds service beyond the lot's platted EDU, e.g. a separate meter; waivable for income-qualified ADUs under the Fee Waiver Program. |
| 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. We pass your request to up to 5 local builders serving San Antonio, where we have them — free, no obligation.
Get San Antonio builder quotes →Permit fees in San Antonio are FY2026 DSD fee schedule (rev. Oct 2025), new residential construction by size: $988 total basic permit fees for 501-1,000 sq ft, $1,022 for 1,001-1,250 and $1,201 for 1,251-1,500 sq ft (building, trade and sewer permits plus a $200 plan review). 100% waivable for income-qualified ADUs.. The review timeline is DSD publishes only its review targets: up to 3 business days for intake/completeness review and up to 3 business days for the first plan-review redlines; the permit issues once corrections are accepted and fees paid (DSD ADU page; DSD fact sheet 3/28/2023). Total time to permit is not published., with plan check: Up to 3 business days to first redline comments (DSD ADU page). Impact fees are The City itself charges no impact fee. SAWS water and wastewater impact fees (effective July 1, 2024; about $7,300-$12,000 per EDU combined, by service area) apply only if the ADU adds service beyond the lot's platted EDU, e.g. a separate meter; waivable for income-qualified ADUs under the Fee Waiver Program.. Pre-approved plans: Yes: 5 Casita Permit-Ready Plans (375, 490, 675, 794 and 800 sq ft), reviewed and approved by DSD as complete building plans; $450 base fee paid to the designer, site-specific changes priced separately; owners at or below 80% AMI can get up to $4,500 design-fee reimbursement.
| 1-Bedroom Rent | $950-$1,250/month |
| 2-Bedroom Rent | $1,200-$1,500/month |
| Annual Rental Income (est.) | $13,200/year |
| Payback Period (est.) | 16.9 years |
| Short-Term Rental | Only with a City STR permit (UDC 35-374.01): Type 1 owner-occupied lot, $300 application, 3-year term, one permit per unit, blockface density caps. |
| Overall ROI Estimate | 4-8% gross rent yield |
A typical ADU in San Antonio generates approximately $13,200 per year in rental income based on average 1-bedroom rents. At an average construction cost of $222,500, the estimated payback period is 16.9 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in San Antonio 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 Antonio: $30,000-$90,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $150,000-$300,000.
3. Pre-approved plans — available in San Antonio, which can save $3,000-$10,000 in design costs and 2-3 months in review time. See which cities offer pre-approved ADU plans.
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.
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