As of October 2026, one published San Antonio guide estimates about $95,000 to $170,000 all-in for a detached ADU, including design, permits and utilities, and about $40,000 to $80,000 in construction for a garage conversion or attached unit. Soil, utility distance, size and finishes decide where a real project falls.
What are the published ranges?
| Item | Published estimate, October 2026 | Source |
|---|---|---|
| Detached ADU, construction | $80,000 to $150,000 | Steadily |
| Detached ADU, all-in | $95,000 to $170,000 | Steadily |
| Garage conversion or attached unit | $40,000 to $80,000 | Steadily |
| Design and drawings | $3,000 to $8,000 | Steadily |
| Utility connections | $5,000 to $20,000 | Steadily |
| 600 sq ft detached, construction | About $73,000 basic, $110,000 mid-range, $152,000 high-end | CostToBuildHouse (RSMeans indices) |
These are third-party estimates, not our prices. Published San Antonio figures run lower than those for Austin, but they vary widely between sources and leave out site-specific work.
It depends: what pushes a San Antonio ADU up or down?
- Foundation. Expansive clay in much of the area, or rock on the north side and toward the Hill Country.
- Utilities. Trench length to the sewer, and whether you choose separate CPS Energy and SAWS meters.
- Setbacks. Building within 5 feet of a side or rear line adds fire-rated wall work.
- Size. Going over 800 sq ft triggers a parking space requirement.
- Finishes. Cabinets, flooring and fixtures can swing a budget widely.
Can fees be waived?
Sometimes. The city may waive development and permitting fees and SAWS impact fees when the home or ADU is rented to a household at or below 80% of area median income for five years. Read the fee waiver guide.
How do I compare builder quotes?
Insist on a written, itemized quote. Check whether it includes drawings, the energy report and HVAC calculations, permit and impact fees, utility work to the unit, and appliances, and how allowances and change orders are handled.
Sources, as of October 2026:
- Steadily, "ADU housing laws and regulations in San Antonio, TX," updated October 1, 2026, for local cost estimates.
- CostToBuildHouse.com, "2026 Texas ADU Cost Guide," for RSMeans-based San Antonio construction estimates.
- City of San Antonio Development Services, Accessory Dwelling Unit Permits page, for setback, parking and fee-waiver rules.