Texas ADU Cost Calculator

What Does It Cost to Build an ADU in Texas?

Texas is among the most affordable states in the country for ADU construction. A detached 800-square-foot ADU with standard finishes typically runs $150,000–$240,000 in Austin, Houston, and the Dallas-Fort Worth metro, and $130,000–$200,000 in San Antonio and the smaller Texas cities. The labor multiplier sits at about 0.92 versus the national baseline, meaning you can often build for 40–50% less than the same structure would cost in California. Austin bucks the trend slightly — the city's tech-driven labor market has pushed framer, electrician, and plumber rates higher, and lead times to book a quality GC stretched during the post-pandemic period. Garage conversions are the most efficient Texas path, often $60,000–$120,000 because land is flat, foundations are slab-on-grade, and the mechanical runs are short.

Texas-Specific Cost Drivers

The biggest cost variance in Texas is heat and hurricane resilience. Houston, Galveston, Beaumont, and Corpus Christi all sit in hurricane-exposed coastal zones, which drives wind-rated roofing, impact-rated windows, and engineered tie-down requirements that can add $8,000–$18,000 versus a similar inland build. Dallas and Austin avoid hurricane rules but face heat-driven HVAC sizing that runs materially larger than Pacific Northwest or Northeast equivalents — a 4-ton system for an 800-square-foot ADU is not unusual in Central Texas, whereas the same unit in Seattle runs 1.5 tons. Soil is another Texas specialty: much of the Austin-San Antonio corridor sits on expansive clay, which requires post-tension slab foundations and occasionally pier-and-beam with additional geotechnical engineering, adding $5,000–$15,000 versus a simple slab on well-drained soil. Offsetting, Texas has no state income tax, no hurricane-zone property tax surcharge, and generally faster inspection cycles than California or Washington.

Permits and the City-By-City Reality

Texas permit fees are remarkably low — typically $800–$3,000 — because cities don't layer impact fees on ADUs the way California does. The harder question is whether your specific city allows them at all. Austin has a robust ADU ordinance with reduced setbacks and compatibility standards. Houston is famously permissive about what you can build on your lot, with no traditional zoning but deed restrictions and lot-coverage rules that do regulate accessory dwellings. San Antonio allows ADUs with a conditional use permit in many residential districts. Dallas has a narrower ADU allowance tied to specific neighborhood zoning. Smaller Texas cities and unincorporated counties often don't explicitly allow ADUs; in those jurisdictions, a second dwelling may be treated as a duplex (requiring different zoning) or may be technically not permitted at all. Timeline from architect-hire to certificate of occupancy is 4–8 months in the major Texas metros, meaningfully faster than Pacific Coast jurisdictions.